Younes BENARIOUA - Academia.edu (original) (raw)
Papers by Younes BENARIOUA
Advanced Science, Engineering and Medicine, Aug 1, 2020
Hard coatings based on chromium carbides and chromium borides are widely used in applications tha... more Hard coatings based on chromium carbides and chromium borides are widely used in applications that require mechanical performance, i.e., high hardness and low friction coefficient and good corrosion resistance. In this work, we made layers of chromium carbides and chromium borides on the surface of low carbon steel through some specific treatments. For chromium carbides, the cementation in a solid medium followed by electroplating of chromium on the surface and finally the application of annealing treatment at temperatures between 500 and 1100 °C for 1 hour. For chromium borides, the boriding treatment in solid medium at 900 °C for 4 hours followed by chromium electroplating on the steel surface and finally the application of annealing treatment at temperatures at 950 °C for 1 and 2 hours. The obtained results show that, in the first case, the cemented layer and the chromium deposited on the surface combine to form chromium carbides on the treated surface after annealing. Similarly, for the second case, boron diffusion and chromium deposition lead to chromium borides on the treated surface. The characteristics of the chromium carbides and chromium borides obtained are very similar to those of chromium carbides and chromium borides obtained by other processes.
Materials Science Forum
Chromium carbide coatings deposited on mechanical parts by different techniques have an interesti... more Chromium carbide coatings deposited on mechanical parts by different techniques have an interesting hardness, wear-resistant and corrosion resistance. Some studies show that chromium carbides produced by physical vapor deposition methods and revealed a superior hardness present a poor adherence to their substrates. The objective of this study is to indirectly obtain a hard, and adherent coating of chromium carbide by using a conversion treatment including carburizing treatment of steel substrate, deposition of a pure chromium layer, and annealing treatment of coated carburized steel under a carbonic gas atmosphere. Treatment temperature has an effect on the partial or complete conversion of chromium film as a result of the diffusion and precipitation process. The transformation rate of chromium into both chromium carbide layers was investigated. For 1 h of holding treatment, chromium film was totally transformed at 900 °C into chromium carbide film which presented high hardness and ...
Materials Science Forum
Boriding is a thermochemical treatment that can be applied to improve the mechanical and chemical... more Boriding is a thermochemical treatment that can be applied to improve the mechanical and chemical properties of steels by surface modification while stilling adequate substrate properties. This kind of treatment is widely used to protect the degradation of the mechanical parts’ surface against wear. The boride atoms introduced into the steel can produce a hard metallic compound formed by diffusion and precipitation. The present study has been conducted in order to obtain an iron borides layer on two types of steel substrates 16NC6 and 20MC5 by using a powder consisting of B4C, NaBF4 and, SiC. The solid boriding treatment was carried out in an electric furnace heated to 950°C for three holding times of 2h, 4h and, 6h. The present research work focuses an the effect studying of holding time as a parameter on the thickness, structure, morphology, and hardness of layers obtained on low carbon steels by the case boriding. As confirmed by structure and microstructure characterization, the...
Newest Updates in Physical Science Research Vol. 14
The present study has been conducted in order to obtain titanium carbide layer using a conversion... more The present study has been conducted in order to obtain titanium carbide layer using a conversion treatment consisting of two main steps. In the first step a thin pure titanium layer was deposited onto 120C4 carbon steel by PVD. In a second step, a vacuum annealing treatment is conducted in order to diffuse the carbon atoms from the substrate toward the titanium coating. As a result, the pure titanium coating is transformed into titanium carbide. However, depending on the annealing temperature, partial or complete conversion into TiC is obtained. Due to that the hardness of the layer depends on the annealing temperature. By a systematic study of the hardness-load variation, the process of the phase transformation of the layer is then confirmed.
Acta Physica Polonica A
The present study has been conducted in order to obtaining chromium boride layers on carbon steel... more The present study has been conducted in order to obtaining chromium boride layers on carbon steel using a conversion processing comprising the following steps: boriding treatment in order to increase the amount of boron atoms in the steel surface, deposition of a thin layer of pure chromium using electrolytic method, and finally an annealing treatment for boron diffusion and formation of boride layer until complete transformation of chromium layer. Depending on the method used (chromium deposition followed by boriding or boriding followed by chromium deposition) and the holding time, the partial or complete conversion is obtained as a result of the diffusion process. The role of the annealing temperature on transformation rates of chromium into chromium boride films was investigated. It is shown that for 1 h at 900 • C, the chromium layer is totally transformed. The scanning electron microscopy analysis and X-ray diffraction showed the presence of CrB and CrB2 chromium borides in addition of FeB and Fe2B iron borides.
International Journal of Thermal and Environmental Engineering
Zinc and some of its alloys have a number of characteristics that make it well suited for use as ... more Zinc and some of its alloys have a number of characteristics that make it well suited for use as a protective coating against the corrosion of steel substrates under severe atmospheric conditions. The metal of zinc, which represents the main galvanization element offer then a cathodic protection to the ferrous materials. Because of these excellent characteristics, galvanization coatings are expected to be used for different protective applications fields. The objective of this work is to study the influence of the nature of steel substrate on the microstructure and the hardness of the intermetallic compounds. The steels used as the substrate are employed in agriculture field as tubes and irrigation elements in pivot. After an optimal preparation of the surface of the substrate by an appropriate roughness process, the steels specimen were immersed in a molten zinc bath maintained at 450°C. The chemical reactions which take place between the steel and the liquid zinc give rise to the ...
Key Engineering Materials, 2022
The use of zinc coatings deposited onto steel is one of the most important commercial processing ... more The use of zinc coatings deposited onto steel is one of the most important commercial processing techniques employed to protect steel components exposed to severe corrosive environments. Our objective is to improve the coated galvanizing steel used as irrigation tube in the agriculture field. After the best mechanical and chemical preparation, the substrates of this steel were galvanized by immersion in a molten zinc bath heated at 450°C during 15 min. the coated steel substrates underwent an annealing treatment in classical furnace heated at 350 °C for various holding times. This research work is to investigate the time effect of annealing treatment on intermetallic compounds of coatings obtained by hot dip galvanizing steel. For this purpose, several characterization means are used to evaluate the change effected by the annealing time on the phases of galvanizing coating. The kinetic growth of each layer relates the thickness to the annealing time by a simple power law. The treatm...
Key Engineering Materials, 2022
The present study has been conducted in order to obtain iron nitrides layer on AISI4140 steel by ... more The present study has been conducted in order to obtain iron nitrides layer on AISI4140 steel by using plasma nitriding treatment. As one of several parameters of this process, the nitrogen rate ranging from 10 to 70% with a step of 20% was chosen. The structure, the morphology, the thickness and the hardness of iron nitrides layer were investigated. As a result, the improvement of surface hardness of nitrided steel was identified related with the increase of compound layer thickness due to the increase of activation rate. The steel substrate treated at high activation rate presents hardness 3 times higher than that of untreated steel.
Recent Trends in Chemical and Material Sciences Vol. 5, 2022
International Journal of Sustainable Water and Environmental Systems, 2016
Carburizing technique has recently been developed to engineer the surfaces of the low steels for ... more Carburizing technique has recently been developed to engineer the surfaces of the low steels for combined improvement in wear and fatigue resistance. The resultant carburized surface region is characterized by the high saturation of carbon in austenite lattices of steel. The duration and temperature of carburising surface hardening treatment can be chosen in agreement with the thermal treatment for obtaining optimal bulk hardness in the precipitation hardening steel. Characterization point of view structural and mechanical of the samples using X-ray diffraction, optical microscopy and micro indentation testing was then introduced in this work. It was found that the incorporation of carbon resulted in a hardened additional compounds consisting of a combination of martensite and expanded austenite.
Novel Perspectives of Engineering Research Vol. 4, 2021
The present work has been conducted in the objective of valorising the zinc from leaching residue... more The present work has been conducted in the objective of valorising the zinc from leaching residues. For this purpose we have retained the goethite method which presented some advantages. The sulfuric acid concentration, temperature and time of treatment are those parameters chosen for this study. The effect of three selected parameters on dissolution of zinc from leaching residues was investigated. It is shown that when values parametric increases the content of zinc increase. R´´. La pr´ esente ´ etude a ´ eten´ ee dans le but de valoriser le zinc des rde lixiviation. Pour ce but, nous avons retenu la m´ ethode goethite qui prcertains avantages. La concentration d'acide sulfurique, la temp´ erature et le temps de traitement ceux sont les param` etres choisis lors de ce travail. L'effet de trois params´ electionn´ es sur la dissolution du zinc des rde lixiviation a ´ et´ ´ etudi´ e. Il est d´ emontr´ e que la teneur en zinc augmente avec l'augmentation des valeurs param´
In order to determine the absolute hardness of film or coating, it is necessary to separate the d... more In order to determine the absolute hardness of film or coating, it is necessary to separate the different contributions. It is known that, depending on the thickness of the film and on the applied load, indentation measurements give apparent hardness values which are the results of contributions by both the substrate and the film. There is a need therefore to separate these two contributions in order to determine the true hardness of the film. Numerous authors have worked on this subject during the past and a large number of models who are written under an additive linear function are available in the literature. This study is to determine the absolute hardness of nitride thin layers obtained by two activation rate plasma of 50 and 65%. A series of classical Vickers indentation at several loads were applied at the surface of the specimens. The true hardness of these thin films was determined by using monolayer model of Jonsson and Hogmark which gives in general cases the concluded r...
Low carbon steel substrates were surface hardened by carburizing in solid medium, and then thin l... more Low carbon steel substrates were surface hardened by carburizing in solid medium, and then thin layers of chromium were deposited by electrolytic way. After chromium deposition, the samples were exposed to isothermal annealing at temperatures between 500 and 1100 °C for 1 and 2 hours duration. The obtained thin layers were characterized by X-rays diffraction, optical microscopy and Vickers micro-hardness. The obtained results showed that chromium layers are transformed into chromium carbide by metastable phases of transition. At 500 °C annealing temperature thin films retain their monophasic character Crα, and they almost keep the same hardness values. When temperature range is between 700 and 900 °C the incipient phase appears and is increased while the chromium mother phases decrease. After annealing at 1100 °C, the chromium layer is completely converted into chromium carbides that would be responsible for the increase of the hardness and adhesion layer / substrate.
Advanced Science, Engineering and Medicine, 2020
Hard coatings based on chromium carbides and chromium borides are widely used in applications tha... more Hard coatings based on chromium carbides and chromium borides are widely used in applications that require mechanical performance, i.e., high hardness and low friction coefficient and good corrosion resistance. In this work, we made layers of chromium carbides and chromium borides on the surface of low carbon steel through some specific treatments. For chromium carbides, the cementation in a solid medium followed by electroplating of chromium on the surface and finally the application of annealing treatment at temperatures between 500 and 1100 °C for 1 hour. For chromium borides, the boriding treatment in solid medium at 900 °C for 4 hours followed by chromium electroplating on the steel surface and finally the application of annealing treatment at temperatures at 950 °C for 1 and 2 hours. The obtained results show that, in the first case, the cemented layer and the chromium deposited on the surface combine to form chromium carbides on the treated surface after annealing. Similarly,...
Journal of Physics: Conference Series, 2018
The surface areas of the parts subjected to mechanical loads influence to a great extent the resi... more The surface areas of the parts subjected to mechanical loads influence to a great extent the resistance to wear and fatigue. In majority of cases, producing of a hard superficial layer on a tough substrate is conducive to an increased resistance to mechanical wear and fatigue. Cementation treatment of low alloy steels which bonds superficial martensitic layer of high hardness and lateral compressive to a core of lower hardness and greater toughness is an example of a good solution of the problem. The high hardness of the martensitic layer is due to an increased concentration of interstitial carbon atoms in the austenite before quenching. The lower hardness of the core after quenching is due to the presence of ferrite and pearlite components which appear if the cooling rate after austenitization becomes lower than the critical on. The objective of the present study was to obtain a cemented surface layer on low alloy steel by means of pack carburizing treatment. Different steel grades, austenitization temperatures as well as different soaking times were used as parameters of the pack carburizing treatment. During this treatment, carbon atoms from the pack powder diffuse toward the steels surface and form compounds of iron carbides. The effect of carburizing parameters on the transformation rate of low carbon surface layer of the low alloy steel to the cemented one was investigated by several analytical techniques.
International Journal of Computational and Experimental Science and Engineering, 2020
Steel substrates low carbons were face-hardened by cementing in case, and then thin layers of chr... more Steel substrates low carbons were face-hardened by cementing in case, and then thin layers of chromium were deposited by electrolytic way on these substrates. After deposition, the samples were exposed to isothermal annealing in the temperature of 950°C. The characterization of the thin layers was made by means of optical microscopy and interferometry Vickers micro-hardness. From the obtained results, we have established the kinetics of phase shift (under effect the layer of cementing) in the thin layers of chromium which are transformed into chromium carbide while passing by metastable phases of transition. These transformations occurred by diffusion of the carbon atoms coming from layer of cementing, germination and growth in solid phase. This fact has examined according to the temperature of annealing, the evolution of the lattice parameter and the morphology of the deposited chromium layer. As regards the mechanical properties, it was established that the micro-hardness believes...
Revue de Métallurgie, 1999
On trouve dans la bibliographie des modeles qui cherchent a representer l’influence du substrat s... more On trouve dans la bibliographie des modeles qui cherchent a representer l’influence du substrat sur la mesure de la durete de film. Dans cet article, nous cherchons a repondre aux questions suivantes : parmi ces modeles, lequel apparait le plus adequat et quel credit peut-on accorder a ses previsions ? Pour tenter de repondre a ces questions, nous analysons des resultats tires de la bibliographie ainsi que des resultats obtenus dans notre laboratoire.
Materials Science and Engineering: A, 2016
For an accurate determination of the materials hardness, instrumented indentation test is undoubt... more For an accurate determination of the materials hardness, instrumented indentation test is undoubtedly the most adequate technique compared to the classical one. However, numerous laboratories or industries have no access to such instrumented device. Consequently, they have no other alternative methods that the use of classical indentation test. However, this technique can lead to wrong interpretation because it does not allow considering the indenter tip defect. In this paper, we suggest to introduce the indenter tip defect into the classical hardness calculation. The proposed methodology is validated on a diamond like-carbon thin film deposited onto a tungsten carbide. Firstly, the truncated indenter tip defect length is estimated from the indentation size effect observed for the substrates which is attributed to the influence of the indenter tip defect. As a result, the tip defect is found to have the same value independently of the tested samples. Afterwards, the tip defect length is introduced into the composite hardness computation and the model of Jönsson and Hogmark is applied to predict film hardness. As a main result, the film hardness is found equal to 37.3 GPa independently of the film thickness and in a good accordance with literature data regarding the diamond hybridization sp3/sp2 ratio.
Surface Engineering, 2016
During the last past decades, galvanised steels have been extensively developed to improve corros... more During the last past decades, galvanised steels have been extensively developed to improve corrosion resistance of steels due to their excellent chemical properties particularly in severe atmospheric conditions. The objective of this work is to predict the hardness-load variation in relation to the bath immersion time using both a multilayer coating hardness model and a layers growth modelling. The kinetic growth of each layer relates the thickness to the immersion time by a simple power law. The hardness of the intermetallic compounds is determined by applying a multilayer hardness model on classical Vickers microindentation data obtained at different indentation loads. Afterwards by combining the kinetic growth laws and the compounds hardness, it is possible to predict the surface hardness-load variation as a function of the immersion bath time.
Advanced Science, Engineering and Medicine, Aug 1, 2020
Hard coatings based on chromium carbides and chromium borides are widely used in applications tha... more Hard coatings based on chromium carbides and chromium borides are widely used in applications that require mechanical performance, i.e., high hardness and low friction coefficient and good corrosion resistance. In this work, we made layers of chromium carbides and chromium borides on the surface of low carbon steel through some specific treatments. For chromium carbides, the cementation in a solid medium followed by electroplating of chromium on the surface and finally the application of annealing treatment at temperatures between 500 and 1100 °C for 1 hour. For chromium borides, the boriding treatment in solid medium at 900 °C for 4 hours followed by chromium electroplating on the steel surface and finally the application of annealing treatment at temperatures at 950 °C for 1 and 2 hours. The obtained results show that, in the first case, the cemented layer and the chromium deposited on the surface combine to form chromium carbides on the treated surface after annealing. Similarly, for the second case, boron diffusion and chromium deposition lead to chromium borides on the treated surface. The characteristics of the chromium carbides and chromium borides obtained are very similar to those of chromium carbides and chromium borides obtained by other processes.
Materials Science Forum
Chromium carbide coatings deposited on mechanical parts by different techniques have an interesti... more Chromium carbide coatings deposited on mechanical parts by different techniques have an interesting hardness, wear-resistant and corrosion resistance. Some studies show that chromium carbides produced by physical vapor deposition methods and revealed a superior hardness present a poor adherence to their substrates. The objective of this study is to indirectly obtain a hard, and adherent coating of chromium carbide by using a conversion treatment including carburizing treatment of steel substrate, deposition of a pure chromium layer, and annealing treatment of coated carburized steel under a carbonic gas atmosphere. Treatment temperature has an effect on the partial or complete conversion of chromium film as a result of the diffusion and precipitation process. The transformation rate of chromium into both chromium carbide layers was investigated. For 1 h of holding treatment, chromium film was totally transformed at 900 °C into chromium carbide film which presented high hardness and ...
Materials Science Forum
Boriding is a thermochemical treatment that can be applied to improve the mechanical and chemical... more Boriding is a thermochemical treatment that can be applied to improve the mechanical and chemical properties of steels by surface modification while stilling adequate substrate properties. This kind of treatment is widely used to protect the degradation of the mechanical parts’ surface against wear. The boride atoms introduced into the steel can produce a hard metallic compound formed by diffusion and precipitation. The present study has been conducted in order to obtain an iron borides layer on two types of steel substrates 16NC6 and 20MC5 by using a powder consisting of B4C, NaBF4 and, SiC. The solid boriding treatment was carried out in an electric furnace heated to 950°C for three holding times of 2h, 4h and, 6h. The present research work focuses an the effect studying of holding time as a parameter on the thickness, structure, morphology, and hardness of layers obtained on low carbon steels by the case boriding. As confirmed by structure and microstructure characterization, the...
Newest Updates in Physical Science Research Vol. 14
The present study has been conducted in order to obtain titanium carbide layer using a conversion... more The present study has been conducted in order to obtain titanium carbide layer using a conversion treatment consisting of two main steps. In the first step a thin pure titanium layer was deposited onto 120C4 carbon steel by PVD. In a second step, a vacuum annealing treatment is conducted in order to diffuse the carbon atoms from the substrate toward the titanium coating. As a result, the pure titanium coating is transformed into titanium carbide. However, depending on the annealing temperature, partial or complete conversion into TiC is obtained. Due to that the hardness of the layer depends on the annealing temperature. By a systematic study of the hardness-load variation, the process of the phase transformation of the layer is then confirmed.
Acta Physica Polonica A
The present study has been conducted in order to obtaining chromium boride layers on carbon steel... more The present study has been conducted in order to obtaining chromium boride layers on carbon steel using a conversion processing comprising the following steps: boriding treatment in order to increase the amount of boron atoms in the steel surface, deposition of a thin layer of pure chromium using electrolytic method, and finally an annealing treatment for boron diffusion and formation of boride layer until complete transformation of chromium layer. Depending on the method used (chromium deposition followed by boriding or boriding followed by chromium deposition) and the holding time, the partial or complete conversion is obtained as a result of the diffusion process. The role of the annealing temperature on transformation rates of chromium into chromium boride films was investigated. It is shown that for 1 h at 900 • C, the chromium layer is totally transformed. The scanning electron microscopy analysis and X-ray diffraction showed the presence of CrB and CrB2 chromium borides in addition of FeB and Fe2B iron borides.
International Journal of Thermal and Environmental Engineering
Zinc and some of its alloys have a number of characteristics that make it well suited for use as ... more Zinc and some of its alloys have a number of characteristics that make it well suited for use as a protective coating against the corrosion of steel substrates under severe atmospheric conditions. The metal of zinc, which represents the main galvanization element offer then a cathodic protection to the ferrous materials. Because of these excellent characteristics, galvanization coatings are expected to be used for different protective applications fields. The objective of this work is to study the influence of the nature of steel substrate on the microstructure and the hardness of the intermetallic compounds. The steels used as the substrate are employed in agriculture field as tubes and irrigation elements in pivot. After an optimal preparation of the surface of the substrate by an appropriate roughness process, the steels specimen were immersed in a molten zinc bath maintained at 450°C. The chemical reactions which take place between the steel and the liquid zinc give rise to the ...
Key Engineering Materials, 2022
The use of zinc coatings deposited onto steel is one of the most important commercial processing ... more The use of zinc coatings deposited onto steel is one of the most important commercial processing techniques employed to protect steel components exposed to severe corrosive environments. Our objective is to improve the coated galvanizing steel used as irrigation tube in the agriculture field. After the best mechanical and chemical preparation, the substrates of this steel were galvanized by immersion in a molten zinc bath heated at 450°C during 15 min. the coated steel substrates underwent an annealing treatment in classical furnace heated at 350 °C for various holding times. This research work is to investigate the time effect of annealing treatment on intermetallic compounds of coatings obtained by hot dip galvanizing steel. For this purpose, several characterization means are used to evaluate the change effected by the annealing time on the phases of galvanizing coating. The kinetic growth of each layer relates the thickness to the annealing time by a simple power law. The treatm...
Key Engineering Materials, 2022
The present study has been conducted in order to obtain iron nitrides layer on AISI4140 steel by ... more The present study has been conducted in order to obtain iron nitrides layer on AISI4140 steel by using plasma nitriding treatment. As one of several parameters of this process, the nitrogen rate ranging from 10 to 70% with a step of 20% was chosen. The structure, the morphology, the thickness and the hardness of iron nitrides layer were investigated. As a result, the improvement of surface hardness of nitrided steel was identified related with the increase of compound layer thickness due to the increase of activation rate. The steel substrate treated at high activation rate presents hardness 3 times higher than that of untreated steel.
Recent Trends in Chemical and Material Sciences Vol. 5, 2022
International Journal of Sustainable Water and Environmental Systems, 2016
Carburizing technique has recently been developed to engineer the surfaces of the low steels for ... more Carburizing technique has recently been developed to engineer the surfaces of the low steels for combined improvement in wear and fatigue resistance. The resultant carburized surface region is characterized by the high saturation of carbon in austenite lattices of steel. The duration and temperature of carburising surface hardening treatment can be chosen in agreement with the thermal treatment for obtaining optimal bulk hardness in the precipitation hardening steel. Characterization point of view structural and mechanical of the samples using X-ray diffraction, optical microscopy and micro indentation testing was then introduced in this work. It was found that the incorporation of carbon resulted in a hardened additional compounds consisting of a combination of martensite and expanded austenite.
Novel Perspectives of Engineering Research Vol. 4, 2021
The present work has been conducted in the objective of valorising the zinc from leaching residue... more The present work has been conducted in the objective of valorising the zinc from leaching residues. For this purpose we have retained the goethite method which presented some advantages. The sulfuric acid concentration, temperature and time of treatment are those parameters chosen for this study. The effect of three selected parameters on dissolution of zinc from leaching residues was investigated. It is shown that when values parametric increases the content of zinc increase. R´´. La pr´ esente ´ etude a ´ eten´ ee dans le but de valoriser le zinc des rde lixiviation. Pour ce but, nous avons retenu la m´ ethode goethite qui prcertains avantages. La concentration d'acide sulfurique, la temp´ erature et le temps de traitement ceux sont les param` etres choisis lors de ce travail. L'effet de trois params´ electionn´ es sur la dissolution du zinc des rde lixiviation a ´ et´ ´ etudi´ e. Il est d´ emontr´ e que la teneur en zinc augmente avec l'augmentation des valeurs param´
In order to determine the absolute hardness of film or coating, it is necessary to separate the d... more In order to determine the absolute hardness of film or coating, it is necessary to separate the different contributions. It is known that, depending on the thickness of the film and on the applied load, indentation measurements give apparent hardness values which are the results of contributions by both the substrate and the film. There is a need therefore to separate these two contributions in order to determine the true hardness of the film. Numerous authors have worked on this subject during the past and a large number of models who are written under an additive linear function are available in the literature. This study is to determine the absolute hardness of nitride thin layers obtained by two activation rate plasma of 50 and 65%. A series of classical Vickers indentation at several loads were applied at the surface of the specimens. The true hardness of these thin films was determined by using monolayer model of Jonsson and Hogmark which gives in general cases the concluded r...
Low carbon steel substrates were surface hardened by carburizing in solid medium, and then thin l... more Low carbon steel substrates were surface hardened by carburizing in solid medium, and then thin layers of chromium were deposited by electrolytic way. After chromium deposition, the samples were exposed to isothermal annealing at temperatures between 500 and 1100 °C for 1 and 2 hours duration. The obtained thin layers were characterized by X-rays diffraction, optical microscopy and Vickers micro-hardness. The obtained results showed that chromium layers are transformed into chromium carbide by metastable phases of transition. At 500 °C annealing temperature thin films retain their monophasic character Crα, and they almost keep the same hardness values. When temperature range is between 700 and 900 °C the incipient phase appears and is increased while the chromium mother phases decrease. After annealing at 1100 °C, the chromium layer is completely converted into chromium carbides that would be responsible for the increase of the hardness and adhesion layer / substrate.
Advanced Science, Engineering and Medicine, 2020
Hard coatings based on chromium carbides and chromium borides are widely used in applications tha... more Hard coatings based on chromium carbides and chromium borides are widely used in applications that require mechanical performance, i.e., high hardness and low friction coefficient and good corrosion resistance. In this work, we made layers of chromium carbides and chromium borides on the surface of low carbon steel through some specific treatments. For chromium carbides, the cementation in a solid medium followed by electroplating of chromium on the surface and finally the application of annealing treatment at temperatures between 500 and 1100 °C for 1 hour. For chromium borides, the boriding treatment in solid medium at 900 °C for 4 hours followed by chromium electroplating on the steel surface and finally the application of annealing treatment at temperatures at 950 °C for 1 and 2 hours. The obtained results show that, in the first case, the cemented layer and the chromium deposited on the surface combine to form chromium carbides on the treated surface after annealing. Similarly,...
Journal of Physics: Conference Series, 2018
The surface areas of the parts subjected to mechanical loads influence to a great extent the resi... more The surface areas of the parts subjected to mechanical loads influence to a great extent the resistance to wear and fatigue. In majority of cases, producing of a hard superficial layer on a tough substrate is conducive to an increased resistance to mechanical wear and fatigue. Cementation treatment of low alloy steels which bonds superficial martensitic layer of high hardness and lateral compressive to a core of lower hardness and greater toughness is an example of a good solution of the problem. The high hardness of the martensitic layer is due to an increased concentration of interstitial carbon atoms in the austenite before quenching. The lower hardness of the core after quenching is due to the presence of ferrite and pearlite components which appear if the cooling rate after austenitization becomes lower than the critical on. The objective of the present study was to obtain a cemented surface layer on low alloy steel by means of pack carburizing treatment. Different steel grades, austenitization temperatures as well as different soaking times were used as parameters of the pack carburizing treatment. During this treatment, carbon atoms from the pack powder diffuse toward the steels surface and form compounds of iron carbides. The effect of carburizing parameters on the transformation rate of low carbon surface layer of the low alloy steel to the cemented one was investigated by several analytical techniques.
International Journal of Computational and Experimental Science and Engineering, 2020
Steel substrates low carbons were face-hardened by cementing in case, and then thin layers of chr... more Steel substrates low carbons were face-hardened by cementing in case, and then thin layers of chromium were deposited by electrolytic way on these substrates. After deposition, the samples were exposed to isothermal annealing in the temperature of 950°C. The characterization of the thin layers was made by means of optical microscopy and interferometry Vickers micro-hardness. From the obtained results, we have established the kinetics of phase shift (under effect the layer of cementing) in the thin layers of chromium which are transformed into chromium carbide while passing by metastable phases of transition. These transformations occurred by diffusion of the carbon atoms coming from layer of cementing, germination and growth in solid phase. This fact has examined according to the temperature of annealing, the evolution of the lattice parameter and the morphology of the deposited chromium layer. As regards the mechanical properties, it was established that the micro-hardness believes...
Revue de Métallurgie, 1999
On trouve dans la bibliographie des modeles qui cherchent a representer l’influence du substrat s... more On trouve dans la bibliographie des modeles qui cherchent a representer l’influence du substrat sur la mesure de la durete de film. Dans cet article, nous cherchons a repondre aux questions suivantes : parmi ces modeles, lequel apparait le plus adequat et quel credit peut-on accorder a ses previsions ? Pour tenter de repondre a ces questions, nous analysons des resultats tires de la bibliographie ainsi que des resultats obtenus dans notre laboratoire.
Materials Science and Engineering: A, 2016
For an accurate determination of the materials hardness, instrumented indentation test is undoubt... more For an accurate determination of the materials hardness, instrumented indentation test is undoubtedly the most adequate technique compared to the classical one. However, numerous laboratories or industries have no access to such instrumented device. Consequently, they have no other alternative methods that the use of classical indentation test. However, this technique can lead to wrong interpretation because it does not allow considering the indenter tip defect. In this paper, we suggest to introduce the indenter tip defect into the classical hardness calculation. The proposed methodology is validated on a diamond like-carbon thin film deposited onto a tungsten carbide. Firstly, the truncated indenter tip defect length is estimated from the indentation size effect observed for the substrates which is attributed to the influence of the indenter tip defect. As a result, the tip defect is found to have the same value independently of the tested samples. Afterwards, the tip defect length is introduced into the composite hardness computation and the model of Jönsson and Hogmark is applied to predict film hardness. As a main result, the film hardness is found equal to 37.3 GPa independently of the film thickness and in a good accordance with literature data regarding the diamond hybridization sp3/sp2 ratio.
Surface Engineering, 2016
During the last past decades, galvanised steels have been extensively developed to improve corros... more During the last past decades, galvanised steels have been extensively developed to improve corrosion resistance of steels due to their excellent chemical properties particularly in severe atmospheric conditions. The objective of this work is to predict the hardness-load variation in relation to the bath immersion time using both a multilayer coating hardness model and a layers growth modelling. The kinetic growth of each layer relates the thickness to the immersion time by a simple power law. The hardness of the intermetallic compounds is determined by applying a multilayer hardness model on classical Vickers microindentation data obtained at different indentation loads. Afterwards by combining the kinetic growth laws and the compounds hardness, it is possible to predict the surface hardness-load variation as a function of the immersion bath time.