Rafał Molak - Profile on Academia.edu (original) (raw)
Papers by Rafał Molak
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016
The paper describes multiscale experimental techniques required for determining the mechanical re... more The paper describes multiscale experimental techniques required for determining the mechanical response of a ferritic-pearlitic steel (14MoV6). Accordingly, five different sets of specimens ranging from macro to micro size scales are utilized and whose experimental results have been compared. Digital image correlation is employed to measure deformations on the surface of the test specimens under tensile loading conditions. The influence of the surface conditions on the residual stress distribution was investigated by means of X-ray synchrotron diffraction. In addition, the effects of specimen size, surface conditions and the number of grains in the cross-section of the specimens on mechanical properties are examined. It is observed that key material parameters including the yield stress, tensile strength and elongation to failure are dependent on specimen size. In addition, the results demonstrate that the number of grains in the cross-section of the specimens significantly influence the material response during uniaxial tensile testing. On the other hand, the surface treatment of the micro tensile test specimens bring about reducing differences in mechanical properties between standard and miniature specimens.
Materials, Sep 7, 2022
The poly(lactic acid) (PLA) biodegradable polymer, as well as natural, siliceous reinforcement in... more The poly(lactic acid) (PLA) biodegradable polymer, as well as natural, siliceous reinforcement in the form of diatomaceous earth, fit perfectly into the circular economy trend. In this study, various kinds of commercial PLA have been reinforced with diatomaceous earth (DE) to prepare biodegradable composites via the extrusion process. The structure of the manufactured composites as well as adhesion between the matrix and the filler were investigated using scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) analyses were carried out to determine crystallinity of PLA matrix as function of DE additions. Additionally, the effect of the ceramic-based reinforcement on the mechanical properties (Young's modulus, elongation to failure, ultimate tensile strength) of PLA has been investigated. The results are discussed in terms of possible applications of PLA + DE composites.
Materials, Sep 23, 2021
In this research, the cold spray process as an additive manufacturing method was applied to depos... more In this research, the cold spray process as an additive manufacturing method was applied to deposit thick titanium coatings onto 7075 aluminium alloy. An analysis of changes in the microstructure and mechanical properties of the coatings depending on the standoff distance was carried out to obtain the maximum deposition efficiency. The process parameters were selected in such a way as to ensure the spraying of irregular titanium powder at the highest velocity and temperature and changing the standoff distance from 20 to 100 mm. Experimental studies demonstrated that the standoff distance had a significant effect on the microstructure of the coatings and their adhesion. Moreover, its rise significantly increased the deposition efficiency. The standoff distance also significantly affected the coating microstructure and their adhesion to the substrate, but did not cause any changes in their phase composition. The standoff distance also influenced the coating porosity, which first decreased to a minimum level of 0.2% and then increased significantly to 9.8%. At the same time, the hardness of the coatings increased by 30%. Numerical simulations confirmed the results of the tests.
Thermal treatment and properties of Ni-SDC cathode for high temperature fuel cells
Materials Science for Energy Technologies, 2023
IM Inżynieria Materiałowa, Jun 28, 2016
The aim of this work was to indicate the influence of changes on the surface of materials caused ... more The aim of this work was to indicate the influence of changes on the surface of materials caused by the corrosive medium (3.5% NaCl solution) on the intensity and character of the Portevin-Le Chatelier effect in model aluminium alloys. For this purpose, two Al alloys, containing 1% and 3% of magnesium, were subjected to tensile testing in the as-cast state and after the exposition in NaCl solution for various time. Several electrochemical measurements were held to determine materials' corrosive behaviour and microscopic observations to evaluate the surface character of the samples. High corrosion resistance of the materials resulted in a very slight alteration of their surface development, which didn't lead into any significant variations in the plastic instability phenomenon PLC.
Effect of annealing on the mechanical and corrosion properties of 316L stainless steel manufactured by laser powder bed fusion
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Dec 1, 2022
Materials
Additive manufacturing (AM) has seen remarkable development in recent years due to relatively hig... more Additive manufacturing (AM) has seen remarkable development in recent years due to relatively high efficiency of the process. Cold spraying (CS) is a particular method of AM, in which titanium and titanium alloy powders are used. CS is a very competitive technology enabling the deposition of coatings, repairing machine parts, and manufacturing new components. For specific applications, the surface of cold-sprayed materials may require further processing. This paper reports an attempt to employ laser surface treatment (LST) of cold-sprayed coatings on an aluminium alloy substrate. The influence of laser beam interaction time on the coatings’ properties was analysed. The microstructure was investigated and observed employing scanning electron microscopy (SEM). To evaluate residual stress after CS and LST, the sin2ψ technique was used. Investigations were also performed on Vickers hardness, contact angle, and surface roughness. Significant changes in the surface morphology of the coati...
Thermal treatment and properties of Ni-SDC cathode for high temperature fuel cells
Materials Science for Energy Technologies
Scientific Reports
Novel metal matrix composites (MMCs) have been fabricated with Ti6Al4V matrix and a biogenic cera... more Novel metal matrix composites (MMCs) have been fabricated with Ti6Al4V matrix and a biogenic ceramic filler in the form of diatomaceous earth (DE). Mixtures of DE and Ti6Al4V powders were consolidated by the spark plasma sintering (SPS) method. Microstructure of the consolidated samples has been investigated with microscopic techniques and XRD. Thermomechanical characteristics have been obtained using small-sample techniques. The results obtained indicate that the fabricated composites show outstanding mechanical and thermal properties due to synergic effects between the filler and the matrix (beyond the rule of mixtures).
Influence of an aluminizing process on the microstructure and tensile strength of the nickel superalloy IN 718 produced by the Selective Laser Melting
Vacuum, 2021
Abstract The paper presents the impact of a surface treatment (an aluminizing process) on the mic... more Abstract The paper presents the impact of a surface treatment (an aluminizing process) on the microstructure and tensile strength of the nickel superalloy IN 718 produced by Selective Laser Melting (SLM). The aluminizing process was carried out by means of chemical vapor deposition with the participation of AlCl3 vapors, in a hydrogen atmosphere as the carrier gas The microstructure of the nickel superalloy IN 718 after 3D printing and thermo-chemical treatment was observed through a optical microscope and an electron scanning microscope. X-ray diffraction made it possible to analyze the phase composition and to determine the residual stresses (sin2Ψ method). Moreover, it was found that the material had a crystalline texture. A static tensile test was carried out on a Zwick/Roell Z005 testing machine. On the basis of the tests, it was ascertained that, with SLM and an appropriate selection of technological parameters, it is possible to obtain a nickel superalloy IN 718 characterized by a fine column microstructure and crystal dendrites. The samples of the nickel superalloy IN 718 produced featured a high strength, similar to that of nickel superalloy IN 718 produced by conventional methods. It was also shown that an aluminizing process carried out by the CVD method makes it possible to attain an intermetallic layer mainly comprised of a AlNi phase characterized by compressive residual stresses. The tensile strength tests proved that the aluminizing process reduced the strength of the nickel alloy IN 718.
Surface and Coatings Technology, 2019
Magnesium alloys are essential materials for aircraft applications however their corrosion protec... more Magnesium alloys are essential materials for aircraft applications however their corrosion protection is still a challenge and restriction from the spread of the applications. Owing to there is still need to search a new way to protect magnesium alloys from corrosion in replacement of currently used chromate coatings which manufacturing process is dangerous and harmful for living organism and will be soon forbidden by law restrictions. In this work, the novel surface modification of magnesium alloy AZ91E was realized. A novel hybrid coating made by combining of the oxide and Diamond-Like Carbon (DLC) layer were elaborated and explored to find out is there any improvements in functional properties when compared to chromate coatings. The corrosion testing in 3.5% NaCl solution and salt fog condition revealed the clear improvements in corrosion protection of AZ91E alloy. Additionally, It was found that oxide coating has lower microhardness and young modulus when compared to DLC and thus it decreases internals stress within the hybrid coating. The wear test revealed that DLC coating significantly improves abrasion resistance when compared to raw, unmodified AZ91 or AZ91E covered with chromate coating.
Surface and Coatings Technology, 2019
Thermally sprayed coatings are one of the potential ways to increase corrosion performance of Mg ... more Thermally sprayed coatings are one of the potential ways to increase corrosion performance of Mg alloys dedicated for aircraft applications. In our research, a novel thermal spray process called Warm Spraying (WS) was used to deposit Ti coatings onto AZ91E magnesium alloy. WS gives us the possibility to control the temperature of the sprayed particles by changing the nitrogen flow rate (NFR) what as a result determine the porosity of WS coatings. The microstructure, porosity and oxygen content of coatings deposited under three different NFR was determined. A relation between porosity, oxygen content and NFR was revealed. The corrosion testing in 3.5 % NaCl solution of assprayed coatings revealed their poor corrosion resistance that led to fast degradation of the substrate. The following post-treatment with epoxy-based polymer resulted in a significant improvement of the corrosion performance of Ti warm sprayed coatings.
Journal of Thermal Spray Technology, Dec 9, 2016
Warm spray is a novel thermal spray technique that allows the formation of dense and relatively p... more Warm spray is a novel thermal spray technique that allows the formation of dense and relatively pure Ti-6Al-4V coatings due to its capability to control the temperature of the propellant gas by diluting the combustion flame with an inert gas such as nitrogen. Recently, its combustion pressure has been increased from 1 to 4 MPa aiming to further increase particle velocity to over 1000 m/ s. Two series of coatings with combustion pressure of 1 and 4 MPa and various nitrogen flow rates were prepared in this study. Effects of combustion pressure and nitrogen flow rate on the microstructure and mechanical properties of the Ti-6Al-4V coatings were systematically studied. Miniature tensile specimens with a total length of about 9 mm were used for static tensile tests. It was found that the spray parameters affect both the porosity and oxygen content of the coatings significantly and had remarkable effects on their mechanical properties. High level of porosity in the Ti-6Al-4V coatings reduced the effective cross-sectional area of the mini-specimens and caused a drop in their tensile strength and Young's modulus. Subsequent heat treatments were found effective in significantly recovering the mechanical properties of the as-sprayed coatings.
Current status and future prospects of warm spray technology☆
Elsevier eBooks, 2015
A modification of high-velocity oxy-fuel (HVOF) thermal spray process named as warm spray (WS) ha... more A modification of high-velocity oxy-fuel (HVOF) thermal spray process named as warm spray (WS) has been developed. By injecting room temperature inert gas into the combustion gas jet of HVOF, the temperature of the propellant gas can be controlled in a range approximately from 2300 to 1000 K so that many powder materials can be deposited in thermally softened state at high impact velocity. In this review, the characteristics of WS process were analyzed by using gas dynamic simulation of the flow field and heating/acceleration of powder particles in comparison with HVOF, cold spray (CS), and high-velocity air-fuel (HVAF) spray. Transmission electron microscopy of WS and CS titanium splats revealed marked differences in the microstructures stemming from the different impact temperatures. Mechanical properties of several metallic coatings formed under different WS and CS conditions were compared. Characteristics of WC-Co coatings made by WS were demonstrated for wear resistant applications.
Journal of Thermal Spray Technology, Nov 3, 2015
The microstructure and mechanical properties of Ti coatings deposited by warm spraying were inves... more The microstructure and mechanical properties of Ti coatings deposited by warm spraying were investigated with the aim to find a set of optimum parameters for the spray process as well as for the subsequent heat treatment. Titanium powder was deposited with different nitrogen flow rates in a range from 0.5 to 1.5 m 3 /min. It was shown that spray parameters, which affect the temperature and velocity of in-flight particles, have significant influence on the fabricated coatings properties. Especially the increase of the warm spraying combustion pressure from 1 to 4 MPa resulted in an increase in the particle velocity to above 1100 m/s. This modification significantly increased the density and was beneficial for controlling the oxygen level in Ti coatings. Miniature tensile specimens with a total length of 9 mm were used to perform tensile tests for the Ti deposits. The optimal mechanical properties were achieved for specimens formed at a middle range of nitrogen flow rate (0.75 m 3 /min). Subsequently, several heat treatments were performed in order to enhance the mechanical properties of the as-sprayed coatings. It was found that the post-spray heat treatment significantly enhanced the strength and elongation of the Ti deposits determined by miniature specimen tensile test.
温間噴霧したTi‐6Al‐4V被覆のミクロ組織と機械的性質に及ぼす噴霧パラメータおよび噴霧後熱処理の効果
Journal of Thermal Spray Technology, 2017
The studies carried out were aimed at developing guidelines for the procedure of employing the Ac... more The studies carried out were aimed at developing guidelines for the procedure of employing the Acoustic Emission (AE) method for ensuring the required manufacturing quality and operating safety of composite bridge structures. For the studies, the experience gathered in the studies of thin-walled components made for the aeronautics, automotive and boatbuilding sectors was used. The focus was components with a significant thickness (14÷16 mm) which are, by their nature, less homogeneous and can have more defects when compared to thin-walled composites. The studies carried out for the purpose of this work demonstrate the system for the acceptance tests of composite structures. The demonstrator model in question was developed based on laboratory tests of composite components and of parts of a prototypical structure under load, as described in this work. The recorded acoustic signals were analyzed using software enabling the authors to analyze numerous parameters of the signals and to lo...
Velocity Measurement of Sprayed Particles and Coatings Fabrication of Titanium Alloys by High Pressure Warm Spray
Asm, May 15, 2013
Materials
Aluminium (Al) and titanium (Ti) coatings were applied on AZ91E magnesium alloy using a low-press... more Aluminium (Al) and titanium (Ti) coatings were applied on AZ91E magnesium alloy using a low-pressure warm spray (WS) method. The deposition was completed using three different nitrogen flow rates (NFR) for both coatings. NFR effects on coating microstructure and other physical properties were systematically studied. Microstructural characterization was performed using scanning electron microscopy (SEM), and the porosity was estimated using two methods—image analysis and X-ray microtomography. The coating adhesion strength, wear resistance, and hardness were examined. The protective properties of the coatings were verified via a salt spray test. Decreasing NFR during coating deposition produced more dense and compact coatings. However, these conditions increased the oxidation of the powder. Al coatings showed lower hardness and wear resistance than Ti coatings, although they are more suitable for corrosion protection due to their low porosity and high compactness.
Journal of KONES, 2018
Remarkable characteristics of high temperature thermoplastic (HTP) matrix used in composite mater... more Remarkable characteristics of high temperature thermoplastic (HTP) matrix used in composite materials reinforced with continuous fibres causes growing application in composite industry. Because of high processing temperature of some semi, crystalline matrix there is limited number of technologies that can be used for part manufacturing. Press forming is an example of technology that allows manufacturing high quality complex parts made of HTP reinforced fibres composite. In order to manufacture part with acceptable quality and mechanical properties, uniform pressure distribution during the process is required. In this article, tooling design process focused on uniform pressure distribution for manufacturing of supporting rib was presented. In order to satisfy this requirement, the rubber stamp was proposed as a tool for manufacturing. Typical press forming process defects were identified and the requirements for rubber stamp were described. It was assumed that the forming process has...
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016
The paper describes multiscale experimental techniques required for determining the mechanical re... more The paper describes multiscale experimental techniques required for determining the mechanical response of a ferritic-pearlitic steel (14MoV6). Accordingly, five different sets of specimens ranging from macro to micro size scales are utilized and whose experimental results have been compared. Digital image correlation is employed to measure deformations on the surface of the test specimens under tensile loading conditions. The influence of the surface conditions on the residual stress distribution was investigated by means of X-ray synchrotron diffraction. In addition, the effects of specimen size, surface conditions and the number of grains in the cross-section of the specimens on mechanical properties are examined. It is observed that key material parameters including the yield stress, tensile strength and elongation to failure are dependent on specimen size. In addition, the results demonstrate that the number of grains in the cross-section of the specimens significantly influence the material response during uniaxial tensile testing. On the other hand, the surface treatment of the micro tensile test specimens bring about reducing differences in mechanical properties between standard and miniature specimens.
Materials, Sep 7, 2022
The poly(lactic acid) (PLA) biodegradable polymer, as well as natural, siliceous reinforcement in... more The poly(lactic acid) (PLA) biodegradable polymer, as well as natural, siliceous reinforcement in the form of diatomaceous earth, fit perfectly into the circular economy trend. In this study, various kinds of commercial PLA have been reinforced with diatomaceous earth (DE) to prepare biodegradable composites via the extrusion process. The structure of the manufactured composites as well as adhesion between the matrix and the filler were investigated using scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) analyses were carried out to determine crystallinity of PLA matrix as function of DE additions. Additionally, the effect of the ceramic-based reinforcement on the mechanical properties (Young's modulus, elongation to failure, ultimate tensile strength) of PLA has been investigated. The results are discussed in terms of possible applications of PLA + DE composites.
Materials, Sep 23, 2021
In this research, the cold spray process as an additive manufacturing method was applied to depos... more In this research, the cold spray process as an additive manufacturing method was applied to deposit thick titanium coatings onto 7075 aluminium alloy. An analysis of changes in the microstructure and mechanical properties of the coatings depending on the standoff distance was carried out to obtain the maximum deposition efficiency. The process parameters were selected in such a way as to ensure the spraying of irregular titanium powder at the highest velocity and temperature and changing the standoff distance from 20 to 100 mm. Experimental studies demonstrated that the standoff distance had a significant effect on the microstructure of the coatings and their adhesion. Moreover, its rise significantly increased the deposition efficiency. The standoff distance also significantly affected the coating microstructure and their adhesion to the substrate, but did not cause any changes in their phase composition. The standoff distance also influenced the coating porosity, which first decreased to a minimum level of 0.2% and then increased significantly to 9.8%. At the same time, the hardness of the coatings increased by 30%. Numerical simulations confirmed the results of the tests.
Thermal treatment and properties of Ni-SDC cathode for high temperature fuel cells
Materials Science for Energy Technologies, 2023
IM Inżynieria Materiałowa, Jun 28, 2016
The aim of this work was to indicate the influence of changes on the surface of materials caused ... more The aim of this work was to indicate the influence of changes on the surface of materials caused by the corrosive medium (3.5% NaCl solution) on the intensity and character of the Portevin-Le Chatelier effect in model aluminium alloys. For this purpose, two Al alloys, containing 1% and 3% of magnesium, were subjected to tensile testing in the as-cast state and after the exposition in NaCl solution for various time. Several electrochemical measurements were held to determine materials' corrosive behaviour and microscopic observations to evaluate the surface character of the samples. High corrosion resistance of the materials resulted in a very slight alteration of their surface development, which didn't lead into any significant variations in the plastic instability phenomenon PLC.
Effect of annealing on the mechanical and corrosion properties of 316L stainless steel manufactured by laser powder bed fusion
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Dec 1, 2022
Materials
Additive manufacturing (AM) has seen remarkable development in recent years due to relatively hig... more Additive manufacturing (AM) has seen remarkable development in recent years due to relatively high efficiency of the process. Cold spraying (CS) is a particular method of AM, in which titanium and titanium alloy powders are used. CS is a very competitive technology enabling the deposition of coatings, repairing machine parts, and manufacturing new components. For specific applications, the surface of cold-sprayed materials may require further processing. This paper reports an attempt to employ laser surface treatment (LST) of cold-sprayed coatings on an aluminium alloy substrate. The influence of laser beam interaction time on the coatings’ properties was analysed. The microstructure was investigated and observed employing scanning electron microscopy (SEM). To evaluate residual stress after CS and LST, the sin2ψ technique was used. Investigations were also performed on Vickers hardness, contact angle, and surface roughness. Significant changes in the surface morphology of the coati...
Thermal treatment and properties of Ni-SDC cathode for high temperature fuel cells
Materials Science for Energy Technologies
Scientific Reports
Novel metal matrix composites (MMCs) have been fabricated with Ti6Al4V matrix and a biogenic cera... more Novel metal matrix composites (MMCs) have been fabricated with Ti6Al4V matrix and a biogenic ceramic filler in the form of diatomaceous earth (DE). Mixtures of DE and Ti6Al4V powders were consolidated by the spark plasma sintering (SPS) method. Microstructure of the consolidated samples has been investigated with microscopic techniques and XRD. Thermomechanical characteristics have been obtained using small-sample techniques. The results obtained indicate that the fabricated composites show outstanding mechanical and thermal properties due to synergic effects between the filler and the matrix (beyond the rule of mixtures).
Influence of an aluminizing process on the microstructure and tensile strength of the nickel superalloy IN 718 produced by the Selective Laser Melting
Vacuum, 2021
Abstract The paper presents the impact of a surface treatment (an aluminizing process) on the mic... more Abstract The paper presents the impact of a surface treatment (an aluminizing process) on the microstructure and tensile strength of the nickel superalloy IN 718 produced by Selective Laser Melting (SLM). The aluminizing process was carried out by means of chemical vapor deposition with the participation of AlCl3 vapors, in a hydrogen atmosphere as the carrier gas The microstructure of the nickel superalloy IN 718 after 3D printing and thermo-chemical treatment was observed through a optical microscope and an electron scanning microscope. X-ray diffraction made it possible to analyze the phase composition and to determine the residual stresses (sin2Ψ method). Moreover, it was found that the material had a crystalline texture. A static tensile test was carried out on a Zwick/Roell Z005 testing machine. On the basis of the tests, it was ascertained that, with SLM and an appropriate selection of technological parameters, it is possible to obtain a nickel superalloy IN 718 characterized by a fine column microstructure and crystal dendrites. The samples of the nickel superalloy IN 718 produced featured a high strength, similar to that of nickel superalloy IN 718 produced by conventional methods. It was also shown that an aluminizing process carried out by the CVD method makes it possible to attain an intermetallic layer mainly comprised of a AlNi phase characterized by compressive residual stresses. The tensile strength tests proved that the aluminizing process reduced the strength of the nickel alloy IN 718.
Surface and Coatings Technology, 2019
Magnesium alloys are essential materials for aircraft applications however their corrosion protec... more Magnesium alloys are essential materials for aircraft applications however their corrosion protection is still a challenge and restriction from the spread of the applications. Owing to there is still need to search a new way to protect magnesium alloys from corrosion in replacement of currently used chromate coatings which manufacturing process is dangerous and harmful for living organism and will be soon forbidden by law restrictions. In this work, the novel surface modification of magnesium alloy AZ91E was realized. A novel hybrid coating made by combining of the oxide and Diamond-Like Carbon (DLC) layer were elaborated and explored to find out is there any improvements in functional properties when compared to chromate coatings. The corrosion testing in 3.5% NaCl solution and salt fog condition revealed the clear improvements in corrosion protection of AZ91E alloy. Additionally, It was found that oxide coating has lower microhardness and young modulus when compared to DLC and thus it decreases internals stress within the hybrid coating. The wear test revealed that DLC coating significantly improves abrasion resistance when compared to raw, unmodified AZ91 or AZ91E covered with chromate coating.
Surface and Coatings Technology, 2019
Thermally sprayed coatings are one of the potential ways to increase corrosion performance of Mg ... more Thermally sprayed coatings are one of the potential ways to increase corrosion performance of Mg alloys dedicated for aircraft applications. In our research, a novel thermal spray process called Warm Spraying (WS) was used to deposit Ti coatings onto AZ91E magnesium alloy. WS gives us the possibility to control the temperature of the sprayed particles by changing the nitrogen flow rate (NFR) what as a result determine the porosity of WS coatings. The microstructure, porosity and oxygen content of coatings deposited under three different NFR was determined. A relation between porosity, oxygen content and NFR was revealed. The corrosion testing in 3.5 % NaCl solution of assprayed coatings revealed their poor corrosion resistance that led to fast degradation of the substrate. The following post-treatment with epoxy-based polymer resulted in a significant improvement of the corrosion performance of Ti warm sprayed coatings.
Journal of Thermal Spray Technology, Dec 9, 2016
Warm spray is a novel thermal spray technique that allows the formation of dense and relatively p... more Warm spray is a novel thermal spray technique that allows the formation of dense and relatively pure Ti-6Al-4V coatings due to its capability to control the temperature of the propellant gas by diluting the combustion flame with an inert gas such as nitrogen. Recently, its combustion pressure has been increased from 1 to 4 MPa aiming to further increase particle velocity to over 1000 m/ s. Two series of coatings with combustion pressure of 1 and 4 MPa and various nitrogen flow rates were prepared in this study. Effects of combustion pressure and nitrogen flow rate on the microstructure and mechanical properties of the Ti-6Al-4V coatings were systematically studied. Miniature tensile specimens with a total length of about 9 mm were used for static tensile tests. It was found that the spray parameters affect both the porosity and oxygen content of the coatings significantly and had remarkable effects on their mechanical properties. High level of porosity in the Ti-6Al-4V coatings reduced the effective cross-sectional area of the mini-specimens and caused a drop in their tensile strength and Young's modulus. Subsequent heat treatments were found effective in significantly recovering the mechanical properties of the as-sprayed coatings.
Current status and future prospects of warm spray technology☆
Elsevier eBooks, 2015
A modification of high-velocity oxy-fuel (HVOF) thermal spray process named as warm spray (WS) ha... more A modification of high-velocity oxy-fuel (HVOF) thermal spray process named as warm spray (WS) has been developed. By injecting room temperature inert gas into the combustion gas jet of HVOF, the temperature of the propellant gas can be controlled in a range approximately from 2300 to 1000 K so that many powder materials can be deposited in thermally softened state at high impact velocity. In this review, the characteristics of WS process were analyzed by using gas dynamic simulation of the flow field and heating/acceleration of powder particles in comparison with HVOF, cold spray (CS), and high-velocity air-fuel (HVAF) spray. Transmission electron microscopy of WS and CS titanium splats revealed marked differences in the microstructures stemming from the different impact temperatures. Mechanical properties of several metallic coatings formed under different WS and CS conditions were compared. Characteristics of WC-Co coatings made by WS were demonstrated for wear resistant applications.
Journal of Thermal Spray Technology, Nov 3, 2015
The microstructure and mechanical properties of Ti coatings deposited by warm spraying were inves... more The microstructure and mechanical properties of Ti coatings deposited by warm spraying were investigated with the aim to find a set of optimum parameters for the spray process as well as for the subsequent heat treatment. Titanium powder was deposited with different nitrogen flow rates in a range from 0.5 to 1.5 m 3 /min. It was shown that spray parameters, which affect the temperature and velocity of in-flight particles, have significant influence on the fabricated coatings properties. Especially the increase of the warm spraying combustion pressure from 1 to 4 MPa resulted in an increase in the particle velocity to above 1100 m/s. This modification significantly increased the density and was beneficial for controlling the oxygen level in Ti coatings. Miniature tensile specimens with a total length of 9 mm were used to perform tensile tests for the Ti deposits. The optimal mechanical properties were achieved for specimens formed at a middle range of nitrogen flow rate (0.75 m 3 /min). Subsequently, several heat treatments were performed in order to enhance the mechanical properties of the as-sprayed coatings. It was found that the post-spray heat treatment significantly enhanced the strength and elongation of the Ti deposits determined by miniature specimen tensile test.
温間噴霧したTi‐6Al‐4V被覆のミクロ組織と機械的性質に及ぼす噴霧パラメータおよび噴霧後熱処理の効果
Journal of Thermal Spray Technology, 2017
The studies carried out were aimed at developing guidelines for the procedure of employing the Ac... more The studies carried out were aimed at developing guidelines for the procedure of employing the Acoustic Emission (AE) method for ensuring the required manufacturing quality and operating safety of composite bridge structures. For the studies, the experience gathered in the studies of thin-walled components made for the aeronautics, automotive and boatbuilding sectors was used. The focus was components with a significant thickness (14÷16 mm) which are, by their nature, less homogeneous and can have more defects when compared to thin-walled composites. The studies carried out for the purpose of this work demonstrate the system for the acceptance tests of composite structures. The demonstrator model in question was developed based on laboratory tests of composite components and of parts of a prototypical structure under load, as described in this work. The recorded acoustic signals were analyzed using software enabling the authors to analyze numerous parameters of the signals and to lo...
Velocity Measurement of Sprayed Particles and Coatings Fabrication of Titanium Alloys by High Pressure Warm Spray
Asm, May 15, 2013
Materials
Aluminium (Al) and titanium (Ti) coatings were applied on AZ91E magnesium alloy using a low-press... more Aluminium (Al) and titanium (Ti) coatings were applied on AZ91E magnesium alloy using a low-pressure warm spray (WS) method. The deposition was completed using three different nitrogen flow rates (NFR) for both coatings. NFR effects on coating microstructure and other physical properties were systematically studied. Microstructural characterization was performed using scanning electron microscopy (SEM), and the porosity was estimated using two methods—image analysis and X-ray microtomography. The coating adhesion strength, wear resistance, and hardness were examined. The protective properties of the coatings were verified via a salt spray test. Decreasing NFR during coating deposition produced more dense and compact coatings. However, these conditions increased the oxidation of the powder. Al coatings showed lower hardness and wear resistance than Ti coatings, although they are more suitable for corrosion protection due to their low porosity and high compactness.
Journal of KONES, 2018
Remarkable characteristics of high temperature thermoplastic (HTP) matrix used in composite mater... more Remarkable characteristics of high temperature thermoplastic (HTP) matrix used in composite materials reinforced with continuous fibres causes growing application in composite industry. Because of high processing temperature of some semi, crystalline matrix there is limited number of technologies that can be used for part manufacturing. Press forming is an example of technology that allows manufacturing high quality complex parts made of HTP reinforced fibres composite. In order to manufacture part with acceptable quality and mechanical properties, uniform pressure distribution during the process is required. In this article, tooling design process focused on uniform pressure distribution for manufacturing of supporting rib was presented. In order to satisfy this requirement, the rubber stamp was proposed as a tool for manufacturing. Typical press forming process defects were identified and the requirements for rubber stamp were described. It was assumed that the forming process has...