Ugur Sen - Academia.edu (original) (raw)
Papers by Ugur Sen
Industrial Lubrication and Tribology, 2009
Surface & Coatings Technology, 2005
In present study, kinetic studies on borided AISI 5140, AISI 4340 and AISI D2 steels are reported... more In present study, kinetic studies on borided AISI 5140, AISI 4340 and AISI D2 steels are reported. Steels were borided in a salt bath consisting of borax, boric acid and ferro-silicon between 1073 and 1273 K for 2, 4, 6 and 8 h. The morphology and types of borides formed on the surface of steel substrates were confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Boride layer thickness formed on the borided steels ranged from 21 to 238 Am depending on process temperature, treatment time and alloying elements of the substrates. The hardness of borides formed on the samples changes between 1077 and 2140 HV 0.1 according to treatment time and temperature. Layer growth kinetics were analyzed by measuring the extent of penetration of FeB and Fe 2 B sublayers as a function of boronizing time and temperature in the range of 1123 -1273 K. The depth of the tips of the most deeply penetrated FeB and Fe 2 B needles are taken as measures for diffusion in the growth directions. The kinetics of the reaction, K = K o exp ( À Q/RT), have also been determined by varying the boriding temperature and time. The results showed that K increase with boriding temperature. Activation energies ( Q) of borided AISI 5140, AISI 4340 and AISI D2 steels at present study were determined as 223, 234 and 170 kJ/mol, respectively. Moreover, an attempt was made to investigate the possibility of predicting the contour diagrams of boride layers variation and to establish some empirical relationships between process parameters and boride layer thicknesses. D
Industrial Lubrication and Tribology, 2005
... properties of boronized GGG-80 ductile cast iron Ugur Sen and Saduman Sen Technical Education... more ... properties of boronized GGG-80 ductile cast iron Ugur Sen and Saduman Sen Technical Education Faculty, Department of Metal Education, Sakarya University, Sakarya, Turkey, and ...Ipek et al. (2000) characterized the wear and friction properties of grey irons. ...
Wear, 2008
In the present study, the wear and friction behavior of AISI 52100 steel and alumina against niob... more In the present study, the wear and friction behavior of AISI 52100 steel and alumina against niobium carbide coated AISI 1040 steel disk was studied using ball-on-disk arrangement. Niobium carbide coating treatment was performed on AISI 1040 steels using thermo-reactive diffusion techniques. The presence of NbC phase in the coating layer was confirmed by X-ray diffraction analysis. Friction and wear tests were carried out at dry test conditions under 2.5, 5 and 10 N loads at 0.1 m/s sliding speed. The results showed that the friction coefficient values are 0.4-0.68 for AISI 52100 steel and 0.4-0.55 for alumina ball, respectively. The specific wear rate of AISI 52100 steel is ranging between 5.66 × 10 −6 and 3.79 × 10 −5 mm 3 /N m. For alumina, it ranges between 3.03 × 10 −8 and 6.36 × 10 −7 mm 3 /N m. In case of alumina running against niobium carbide coated disk, the wear rate obtained from wear tracks on the disk is ranging between 1.44 × 10 −6 and 7.55 × 10 −6 mm 3 /N m. In general, the coefficient of friction and wear rate increased with the increase in load value.
Vacuum, 2003
GGG-50, GGG-60 and GGG-80 ductile cast irons containing 0.01, 0.3 and 0.98wt% copper, respectivel... more GGG-50, GGG-60 and GGG-80 ductile cast irons containing 0.01, 0.3 and 0.98wt% copper, respectively, were boronized in a salt bath and then analyzed using optical microscopy, scanning electron microscopy and X-ray diffraction analysis. Increasing copper concentration in ductile cast irons resulted in formation of mono-phase boride layer (Fe2B), decreased Si-ferrite zone and hindered the growth discontinuous graphite between boride layer
Materials Letters, 2008
In this study, niobium boride coating was applied on pre-boronized AISI M2 steel by the thermo-re... more In this study, niobium boride coating was applied on pre-boronized AISI M2 steel by the thermo-reactive deposition technique in a powder mixture consisting of ferro-niobium, ammonium chloride and alumina at 950°C for 1-4 h. The coated samples were characterized by X-ray diffraction, scanning electron microscope and micro-hardness tests. Niobium boride layer formed on the pre-boronized AISI M2 steel was smooth, compact and homogeneous. X-ray studies showed that the phases formed on the steel surfaces are NbB, Nb 3 B 2 , FeB and Fe 2 B. The depth of the niobium boride layer ranged from 0.97 μm to 3.25 μm, depending on treatment time. The higher the treatment time the thicker the niobium boride layer observed. The hardness of the niobium boride layer was 2738 ± 353 HV 0.01 .
Ceramics International, 2011
In the present study, the effect of SiC addition on properties of basalt base glass–ceramic coati... more In the present study, the effect of SiC addition on properties of basalt base glass–ceramic coating was investigated. SiC reinforced glass–ceramic coating was realized by atmospheric air plasma spray coating technique on AISI 1040 steel pre-coated with Ni+5wt.%Al bond coat. Composite powder mixture consisted of 10%, 20% and 30% SiC by weight were used for coating treatment. Controlled heat treatment
Key Engineering Materials, 2004
Vacuum, 2005
The growth kinetics of boride layer on boronized AISI 4140 steel is reported. Steel samples were ... more The growth kinetics of boride layer on boronized AISI 4140 steel is reported. Steel samples were boronized in molten borax, boric acid and ferro-silicon bath at 1123, 1173 and 1223 K for 2, 4, 6 and 8 h, respectively. The morphology and types of borides formed on the surface of AISI 4140 steel substrate were analyzed by means of optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analysis (XRD). The boride layer thickness ranged from 38.4 to 225 mm. Iso-thickness diagrams for pre-determined thickness according to treatment time and temperature, were graphed by MATLAB 6.0 software. The hardness of borides formed on the samples changed between 1446 and 1739 HV 0.1 , according to treatment time and temperature. Layer growth kinetics way analyzed by measuring the extent of penetration of FeB and Fe 2 B sublayers as a function of treatment time and temperature in the range of 1123-1223 K. For practical use, an iso hardness diagram was established as a function of treatment time, temperature and boride layer thickness. The depth of the tips of the most deeply penetrated FeB and Fe 2 B needles were taken as measures for diffusion in the growth directions. The kinetics of the reaction, K ¼ K o expðÀQ=RTÞ were also determined by varying the treatment temperature and time. The results show that K increased with boronizing temperature. The activation energy (Q) was formed to be 215 kJ mol À1 . The growth rate constant (K) ranged from 3  10 À9 to 2  10 À8 cm 2 s À1 .
Surface & Coatings Technology, 2004
In this work, some surface properties of ductile irons were improved by a thermo-chemical boroniz... more In this work, some surface properties of ductile irons were improved by a thermo-chemical boronizing process. Boronizing was performed in a slurry salt bath consisting of borax, boric acid and ferro-silicon at 850 and 950 °C for 28 h. Three different ductile irons namely GGG 50, ...
Vacuum, 2007
In this study, chromium nitride coating was realized on AISI 1010 steels by nitro-chromizing trea... more In this study, chromium nitride coating was realized on AISI 1010 steels by nitro-chromizing treatment. Steel samples were tufftrided at 575 1C for 2 h in the first step of the coating process, and then chromized by pack method in the powder mixture consisting of ferrochromium, ammonium chloride and alumina at 1000 1C for 1-4 h. Samples were characterized by scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy, X-ray diffraction (XRD) analysis and Vickers micro-hardness tests. Coating layer formed on the steel samples is smooth and compact and well bonded to the steel matrix. The thickness of chromium nitride layer formed on the steel samples ranged from 5.1671.48 to 13.4571.73 mm, depending on the treatment time. The average micro-hardness value of the layer was 1789759 HV 0.05 . The layer consisted of Cr 2 N and (Cr,Fe) 2 N (1Àx) phases, according to XRD. EDS results showed that coating layer includes chromium and nitrogen. r
Materials Letters, 2006
In this study, we investigated the wear behaviour of borided and borided + short-duration oxidize... more In this study, we investigated the wear behaviour of borided and borided + short-duration oxidized AISI 4140 steel. Boronizing was carried out in a slurry salt bath consisting of borax, boric acid and ferro silicon. Also, short-duration oxidizing treatment was applied to borided steel to produce glass-like boron oxide layer. The short-duration oxidizing was performed at 750°C for 3 min. Optical and scanning electron microscope (SEM) cross-sectional examinations of borided layer revealed a needle-shaped morphology. The presence of non-oxide boride type ceramics FeB and Fe 2 B formed on the surface of steel substrate was confirmed by classical metallographic technique and X-ray diffraction (XRD) analysis. The hardness of borides formed on the surface of steel substrate and unborided steel substrate were 1446-1690 HV 0.1 and 280 HV 0.1 , respectively. The wear behaviour of borided steel were characterised by using a pin-on-disc technique. The borided and short-duration oxidized steels, in the form of pins were allowed to slide against a hard AISI 440C stainless steel disc (63 HRc). The sliding velocity of 1 m s − 1 for borided and short-duration oxidized steel and the nominal load on the pin was 20 N. The highest wear rates were observed on disc slide against the base steel, whilst the lowest wear rates occurred during sliding against the borided and short-duration oxidized steel surfaces. It was observed that the friction coefficient of unborided (hardened + tempered) and borided steels ranged from 0.50 to 0.60, but after short-duration oxidizing, the friction coefficient of borided steel was dropped to 0.12.
Materials Characterization, 2003
In this study, the fracture toughness of boride layers of two borided cold work tool steels have ... more In this study, the fracture toughness of boride layers of two borided cold work tool steels have been investigated. Boriding was carried out in a salt bath consisting of borax, boric acid, ferro-silicon and aluminum. Boriding was performed at 850 and 950 jC for 2 to 7 h. The presence of boride phases were determined by X-ray diffraction (XRD) analysis. Hardness and fracture toughness of borides were measured via Vickers indenter. Increasing of boriding time and temperature leads to reduction of fracture toughness of borides. Metallographic examination showed that boride layer formed on cold work tool steels was compact and smooth. D
Key Engineering Materials, 2004
Materials & Design, 2006
... J Euro Ceram Soc, 17 (1997), pp. 147–152. [13] S. Yılmaz, M. Ipek, G. Celebi and C. Bindal, T... more ... J Euro Ceram Soc, 17 (1997), pp. 147–152. [13] S. Yılmaz, M. Ipek, G. Celebi and C. Bindal, The effect of bond coat on mechanical properties of plasma sprayed Al 2 O 3 and Al 2 O 3 –13 wt% TiO 2 coatings on AISI 316L stainless steel. Vacuum, 77 (2005), pp. 315–321. ...
Journal of Materials Processing Technology, 2004
In this study, some properties of borided perlitic ductile irons were investigated. Boronizing wa... more In this study, some properties of borided perlitic ductile irons were investigated. Boronizing was realized in a salt bath and appropriate boronizing heat treatment was carried out between under atmospheric pressure. Borides eg FeB, Fe 2 B formed on ductile iron was verified by x-ray ...
Industrial Lubrication and Tribology, 2009
Surface & Coatings Technology, 2005
In present study, kinetic studies on borided AISI 5140, AISI 4340 and AISI D2 steels are reported... more In present study, kinetic studies on borided AISI 5140, AISI 4340 and AISI D2 steels are reported. Steels were borided in a salt bath consisting of borax, boric acid and ferro-silicon between 1073 and 1273 K for 2, 4, 6 and 8 h. The morphology and types of borides formed on the surface of steel substrates were confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Boride layer thickness formed on the borided steels ranged from 21 to 238 Am depending on process temperature, treatment time and alloying elements of the substrates. The hardness of borides formed on the samples changes between 1077 and 2140 HV 0.1 according to treatment time and temperature. Layer growth kinetics were analyzed by measuring the extent of penetration of FeB and Fe 2 B sublayers as a function of boronizing time and temperature in the range of 1123 -1273 K. The depth of the tips of the most deeply penetrated FeB and Fe 2 B needles are taken as measures for diffusion in the growth directions. The kinetics of the reaction, K = K o exp ( À Q/RT), have also been determined by varying the boriding temperature and time. The results showed that K increase with boriding temperature. Activation energies ( Q) of borided AISI 5140, AISI 4340 and AISI D2 steels at present study were determined as 223, 234 and 170 kJ/mol, respectively. Moreover, an attempt was made to investigate the possibility of predicting the contour diagrams of boride layers variation and to establish some empirical relationships between process parameters and boride layer thicknesses. D
Industrial Lubrication and Tribology, 2009
Surface & Coatings Technology, 2005
In present study, kinetic studies on borided AISI 5140, AISI 4340 and AISI D2 steels are reported... more In present study, kinetic studies on borided AISI 5140, AISI 4340 and AISI D2 steels are reported. Steels were borided in a salt bath consisting of borax, boric acid and ferro-silicon between 1073 and 1273 K for 2, 4, 6 and 8 h. The morphology and types of borides formed on the surface of steel substrates were confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Boride layer thickness formed on the borided steels ranged from 21 to 238 Am depending on process temperature, treatment time and alloying elements of the substrates. The hardness of borides formed on the samples changes between 1077 and 2140 HV 0.1 according to treatment time and temperature. Layer growth kinetics were analyzed by measuring the extent of penetration of FeB and Fe 2 B sublayers as a function of boronizing time and temperature in the range of 1123 -1273 K. The depth of the tips of the most deeply penetrated FeB and Fe 2 B needles are taken as measures for diffusion in the growth directions. The kinetics of the reaction, K = K o exp ( À Q/RT), have also been determined by varying the boriding temperature and time. The results showed that K increase with boriding temperature. Activation energies ( Q) of borided AISI 5140, AISI 4340 and AISI D2 steels at present study were determined as 223, 234 and 170 kJ/mol, respectively. Moreover, an attempt was made to investigate the possibility of predicting the contour diagrams of boride layers variation and to establish some empirical relationships between process parameters and boride layer thicknesses. D
Industrial Lubrication and Tribology, 2005
... properties of boronized GGG-80 ductile cast iron Ugur Sen and Saduman Sen Technical Education... more ... properties of boronized GGG-80 ductile cast iron Ugur Sen and Saduman Sen Technical Education Faculty, Department of Metal Education, Sakarya University, Sakarya, Turkey, and ...Ipek et al. (2000) characterized the wear and friction properties of grey irons. ...
Wear, 2008
In the present study, the wear and friction behavior of AISI 52100 steel and alumina against niob... more In the present study, the wear and friction behavior of AISI 52100 steel and alumina against niobium carbide coated AISI 1040 steel disk was studied using ball-on-disk arrangement. Niobium carbide coating treatment was performed on AISI 1040 steels using thermo-reactive diffusion techniques. The presence of NbC phase in the coating layer was confirmed by X-ray diffraction analysis. Friction and wear tests were carried out at dry test conditions under 2.5, 5 and 10 N loads at 0.1 m/s sliding speed. The results showed that the friction coefficient values are 0.4-0.68 for AISI 52100 steel and 0.4-0.55 for alumina ball, respectively. The specific wear rate of AISI 52100 steel is ranging between 5.66 × 10 −6 and 3.79 × 10 −5 mm 3 /N m. For alumina, it ranges between 3.03 × 10 −8 and 6.36 × 10 −7 mm 3 /N m. In case of alumina running against niobium carbide coated disk, the wear rate obtained from wear tracks on the disk is ranging between 1.44 × 10 −6 and 7.55 × 10 −6 mm 3 /N m. In general, the coefficient of friction and wear rate increased with the increase in load value.
Vacuum, 2003
GGG-50, GGG-60 and GGG-80 ductile cast irons containing 0.01, 0.3 and 0.98wt% copper, respectivel... more GGG-50, GGG-60 and GGG-80 ductile cast irons containing 0.01, 0.3 and 0.98wt% copper, respectively, were boronized in a salt bath and then analyzed using optical microscopy, scanning electron microscopy and X-ray diffraction analysis. Increasing copper concentration in ductile cast irons resulted in formation of mono-phase boride layer (Fe2B), decreased Si-ferrite zone and hindered the growth discontinuous graphite between boride layer
Materials Letters, 2008
In this study, niobium boride coating was applied on pre-boronized AISI M2 steel by the thermo-re... more In this study, niobium boride coating was applied on pre-boronized AISI M2 steel by the thermo-reactive deposition technique in a powder mixture consisting of ferro-niobium, ammonium chloride and alumina at 950°C for 1-4 h. The coated samples were characterized by X-ray diffraction, scanning electron microscope and micro-hardness tests. Niobium boride layer formed on the pre-boronized AISI M2 steel was smooth, compact and homogeneous. X-ray studies showed that the phases formed on the steel surfaces are NbB, Nb 3 B 2 , FeB and Fe 2 B. The depth of the niobium boride layer ranged from 0.97 μm to 3.25 μm, depending on treatment time. The higher the treatment time the thicker the niobium boride layer observed. The hardness of the niobium boride layer was 2738 ± 353 HV 0.01 .
Ceramics International, 2011
In the present study, the effect of SiC addition on properties of basalt base glass–ceramic coati... more In the present study, the effect of SiC addition on properties of basalt base glass–ceramic coating was investigated. SiC reinforced glass–ceramic coating was realized by atmospheric air plasma spray coating technique on AISI 1040 steel pre-coated with Ni+5wt.%Al bond coat. Composite powder mixture consisted of 10%, 20% and 30% SiC by weight were used for coating treatment. Controlled heat treatment
Key Engineering Materials, 2004
Vacuum, 2005
The growth kinetics of boride layer on boronized AISI 4140 steel is reported. Steel samples were ... more The growth kinetics of boride layer on boronized AISI 4140 steel is reported. Steel samples were boronized in molten borax, boric acid and ferro-silicon bath at 1123, 1173 and 1223 K for 2, 4, 6 and 8 h, respectively. The morphology and types of borides formed on the surface of AISI 4140 steel substrate were analyzed by means of optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analysis (XRD). The boride layer thickness ranged from 38.4 to 225 mm. Iso-thickness diagrams for pre-determined thickness according to treatment time and temperature, were graphed by MATLAB 6.0 software. The hardness of borides formed on the samples changed between 1446 and 1739 HV 0.1 , according to treatment time and temperature. Layer growth kinetics way analyzed by measuring the extent of penetration of FeB and Fe 2 B sublayers as a function of treatment time and temperature in the range of 1123-1223 K. For practical use, an iso hardness diagram was established as a function of treatment time, temperature and boride layer thickness. The depth of the tips of the most deeply penetrated FeB and Fe 2 B needles were taken as measures for diffusion in the growth directions. The kinetics of the reaction, K ¼ K o expðÀQ=RTÞ were also determined by varying the treatment temperature and time. The results show that K increased with boronizing temperature. The activation energy (Q) was formed to be 215 kJ mol À1 . The growth rate constant (K) ranged from 3  10 À9 to 2  10 À8 cm 2 s À1 .
Surface & Coatings Technology, 2004
In this work, some surface properties of ductile irons were improved by a thermo-chemical boroniz... more In this work, some surface properties of ductile irons were improved by a thermo-chemical boronizing process. Boronizing was performed in a slurry salt bath consisting of borax, boric acid and ferro-silicon at 850 and 950 °C for 28 h. Three different ductile irons namely GGG 50, ...
Vacuum, 2007
In this study, chromium nitride coating was realized on AISI 1010 steels by nitro-chromizing trea... more In this study, chromium nitride coating was realized on AISI 1010 steels by nitro-chromizing treatment. Steel samples were tufftrided at 575 1C for 2 h in the first step of the coating process, and then chromized by pack method in the powder mixture consisting of ferrochromium, ammonium chloride and alumina at 1000 1C for 1-4 h. Samples were characterized by scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy, X-ray diffraction (XRD) analysis and Vickers micro-hardness tests. Coating layer formed on the steel samples is smooth and compact and well bonded to the steel matrix. The thickness of chromium nitride layer formed on the steel samples ranged from 5.1671.48 to 13.4571.73 mm, depending on the treatment time. The average micro-hardness value of the layer was 1789759 HV 0.05 . The layer consisted of Cr 2 N and (Cr,Fe) 2 N (1Àx) phases, according to XRD. EDS results showed that coating layer includes chromium and nitrogen. r
Materials Letters, 2006
In this study, we investigated the wear behaviour of borided and borided + short-duration oxidize... more In this study, we investigated the wear behaviour of borided and borided + short-duration oxidized AISI 4140 steel. Boronizing was carried out in a slurry salt bath consisting of borax, boric acid and ferro silicon. Also, short-duration oxidizing treatment was applied to borided steel to produce glass-like boron oxide layer. The short-duration oxidizing was performed at 750°C for 3 min. Optical and scanning electron microscope (SEM) cross-sectional examinations of borided layer revealed a needle-shaped morphology. The presence of non-oxide boride type ceramics FeB and Fe 2 B formed on the surface of steel substrate was confirmed by classical metallographic technique and X-ray diffraction (XRD) analysis. The hardness of borides formed on the surface of steel substrate and unborided steel substrate were 1446-1690 HV 0.1 and 280 HV 0.1 , respectively. The wear behaviour of borided steel were characterised by using a pin-on-disc technique. The borided and short-duration oxidized steels, in the form of pins were allowed to slide against a hard AISI 440C stainless steel disc (63 HRc). The sliding velocity of 1 m s − 1 for borided and short-duration oxidized steel and the nominal load on the pin was 20 N. The highest wear rates were observed on disc slide against the base steel, whilst the lowest wear rates occurred during sliding against the borided and short-duration oxidized steel surfaces. It was observed that the friction coefficient of unborided (hardened + tempered) and borided steels ranged from 0.50 to 0.60, but after short-duration oxidizing, the friction coefficient of borided steel was dropped to 0.12.
Materials Characterization, 2003
In this study, the fracture toughness of boride layers of two borided cold work tool steels have ... more In this study, the fracture toughness of boride layers of two borided cold work tool steels have been investigated. Boriding was carried out in a salt bath consisting of borax, boric acid, ferro-silicon and aluminum. Boriding was performed at 850 and 950 jC for 2 to 7 h. The presence of boride phases were determined by X-ray diffraction (XRD) analysis. Hardness and fracture toughness of borides were measured via Vickers indenter. Increasing of boriding time and temperature leads to reduction of fracture toughness of borides. Metallographic examination showed that boride layer formed on cold work tool steels was compact and smooth. D
Key Engineering Materials, 2004
Materials & Design, 2006
... J Euro Ceram Soc, 17 (1997), pp. 147–152. [13] S. Yılmaz, M. Ipek, G. Celebi and C. Bindal, T... more ... J Euro Ceram Soc, 17 (1997), pp. 147–152. [13] S. Yılmaz, M. Ipek, G. Celebi and C. Bindal, The effect of bond coat on mechanical properties of plasma sprayed Al 2 O 3 and Al 2 O 3 –13 wt% TiO 2 coatings on AISI 316L stainless steel. Vacuum, 77 (2005), pp. 315–321. ...
Journal of Materials Processing Technology, 2004
In this study, some properties of borided perlitic ductile irons were investigated. Boronizing wa... more In this study, some properties of borided perlitic ductile irons were investigated. Boronizing was realized in a salt bath and appropriate boronizing heat treatment was carried out between under atmospheric pressure. Borides eg FeB, Fe 2 B formed on ductile iron was verified by x-ray ...
Industrial Lubrication and Tribology, 2009
Surface & Coatings Technology, 2005
In present study, kinetic studies on borided AISI 5140, AISI 4340 and AISI D2 steels are reported... more In present study, kinetic studies on borided AISI 5140, AISI 4340 and AISI D2 steels are reported. Steels were borided in a salt bath consisting of borax, boric acid and ferro-silicon between 1073 and 1273 K for 2, 4, 6 and 8 h. The morphology and types of borides formed on the surface of steel substrates were confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Boride layer thickness formed on the borided steels ranged from 21 to 238 Am depending on process temperature, treatment time and alloying elements of the substrates. The hardness of borides formed on the samples changes between 1077 and 2140 HV 0.1 according to treatment time and temperature. Layer growth kinetics were analyzed by measuring the extent of penetration of FeB and Fe 2 B sublayers as a function of boronizing time and temperature in the range of 1123 -1273 K. The depth of the tips of the most deeply penetrated FeB and Fe 2 B needles are taken as measures for diffusion in the growth directions. The kinetics of the reaction, K = K o exp ( À Q/RT), have also been determined by varying the boriding temperature and time. The results showed that K increase with boriding temperature. Activation energies ( Q) of borided AISI 5140, AISI 4340 and AISI D2 steels at present study were determined as 223, 234 and 170 kJ/mol, respectively. Moreover, an attempt was made to investigate the possibility of predicting the contour diagrams of boride layers variation and to establish some empirical relationships between process parameters and boride layer thicknesses. D