Yazar "Gunen, Ali" seçeneğine göre listele
Listeleniyor 1 - 18 / 18
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Characteristics and high temperature wear behavior of chrome vanadium carbide composite coatings produced by thermo-reactive diffusion(Elsevier Science Sa, 2020) Gunen, Ali; Kalkandelen, Muge; Gok, Mustafa Sabri; Kanca, Erdogan; Kurt, Bulent; Karakas, Mustafa Serdar; Karahan, Ismail HakkiIn this study, Cr-V-C composite carbide layers were grown on the surface of a GGG-80 ductile iron using thermoreactive diffusion (TRD). The TRD process was carried out at temperatures of 900, 1000, and 1100 degrees C for 1 h using nano-sized Fe-V and Fe-Cr powders. The coatings were characterized by X-ray diffractometry (XRD), 2D profilometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), microhardness measurements, nanoindentation, and wear tests. The wear tests were performed on untreated and coated samples using a ball-on-disc type wear tester under 10 N load at four different temperatures (25 degrees C, 250 degrees C, 500 degrees C and 750 degrees C) against a 6-mm WC ball. Metallographic investigations revealed that the graphite nodules near the surface were dissolved as a result of the TRD process. Depending on the TRD process temperature, a coating with a thickness of 12-36 mu m, hardness of 24.14-31.38 GPa, and elastic modulus of 198-233 GPa was obtained. An increase in process temperature increased the thickness, hardness, and elastic modulus of the obtained Cr-V-C layers, which resulted in low friction coefficient values and decreased wear rates. Although all coated samples showed improved wear resistance in all wear test conditions, the wear rates were significantly increased at 750 degrees C due to flaking.Öğe Characterizations and Kinetics of Refractory Niobium Carbide Coatings on AISI D3 Steel(Springer, 2023) Gunen, Ali; Acikgoz, Hasan Huseyin; Keddam, Mourad; Karahan, Ismail HakkiNiobium carbide (NbC) coatings were carried out by means of the thermo-reactive diffusion (TRD) on AISI D3 cold work tool steel, in the powder mixture composed of 25 wt.% ferro-niobium, 70 wt.% alumina and 7.5 wt.% ammonium chloride at 1173, 1273 and 1373 K for 2, 4 and 6 h. NbC coatings were inspected with scanning electron microscopy, x-ray diffractometer, Vickers micro-hardness testing. Homogeneous, crack-free and uniform NbC coatings with 8.75-17.10 mu m thickness and 1586-2263 HV0.025 hardness were obtained on AISI D3 steel by TRD process. The integral method-based model was used for studying the carbon diffusion by forming NbC coatings. The value of 45.93 kJ mol(-1) was determined as the necessary activation energy required for the niobizing process of AISI D3 steel.Öğe A Comparative Study on the Effects of Different Thermochemical Coating Techniques on Corrosion Resistance of STKM-13A Steel(Springer, 2018) Gunen, Ali; Kanca, Yusuf; Karahan, Ismail Hakki; Karakas, Mustafa Serdar; Gok, Mustafa Sabri; Kanca, Erdogan; Curuk, AhmetThe corrosion resistances of three different thermochemical coatings (grown using titanizing, boriding, and borotitanizing treatments) applied to STKM-13A steel surfaces were investigated. The coatings were characterized using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, 2D profilometry, and microhardness experiments. The corrosion tests were conducted using both electrochemical and static immersion methods, in 3.5 pct NaCl and 40 pct HF acid solutions, respectively. The corrosion resistance of STKM-13A steel was enhanced after the coating process. The specimens were exposed to more corrosion in the HF solution than in the NaCl solution. The best corrosion resistance was obtained in the borotitanized and borided specimens immersed in the NaCl and HF solutions, respectively. The borided STKM-13A steel sample showed even less cumulative weight loss than Inconel 625 in the static immersion HF acid solution test. This suggests potential use of the borided STKM-13A steel in the uranium production units of nuclear power plants as an alternative to more costly alternatives such as Monel, Inconel, and Hastelloy. (C) The Minerals, Metals & Materials Society and ASM International 2018Öğe Corrosion behaviour of borided AISI 304 austenitic stainless steel(Emerald Group Publishing Ltd, 2014) Gunen, Ali; Karakas, Mustafa Serdar; Kurt, Bulent; Calik, AdnanPurpose - The paper aims to clarify the effect of bonding on the corrosion behavior and mechanical properties of AISI 304 austenitic stainless steel. Design/methodology/approach - The commercially available steel was subjected to a bonding treatment with Ekabor III powders at temperatures of 1,223-1,273 K with bonding durations of 2-4 h. Microstructural characterization of the steel was carried out with optical microscopy, scanning electron microscopy and X-ray diffraction analyses. Static immersion corrosion tests were made using a 10 percent H2SO4 acid solution and salt spray tests were carried out in accord with the ASTM B-117 standard. Findings - Grain boundary precipitation of carbides was observed in the transition zone beneath the boride layers. The corrosion resistance of the steel against the acid solution increased to about seven times its untreated value with the bonding treatment. Research limitations/implications - The boride coating improved the corrosion resistance of the AISI 304 stainless steel against acidic media, but suffered from spalling in the salt spray test. Future work will focus on improving the adhesion between the coating and the substrate by changing the parameters for the bonding process. Practical implications - Pack bonding is a simple, environmentally friendly coating process and can be recommended for use in small and medium enterprises. The boride coatings deposited have potential in further improving the wear and corrosion resistance of stainless steels. Originality/value - The outcome of the research is of great importance for the industry using wear- and corrosion-resistant coatings.Öğe Determination of fracture toughness of boride layers grown on Co1.21Cr1.82Fe1.44Mn1.32Ni1.12Al0.08B0.01 high entropy alloy by nanoindentation(Elsevier Sci Ltd, 2022) Gunen, Ali; Makuch, Natalia; Altinay, Yasemin; Carboga, Cemal; Dal, Serkan; Karaca, YusufMultiphase boride layers consisting of (CoFe)2B, (Fe0.4Mn0.6)B, Cr2Ni3B6 and (Cr0.4Mn0.6)B were formed on the surface of Co1.21Cr1.82Fe1.44Mn1.32Ni1.12Al0.08B0.01 high entropy alloy by powder-pack boronizing at 900 degrees C, 950 degrees C and 1000 degrees C for 4 h. The nanohardness (H), modulus of elasticity (E) and fracture toughness (KC) of the multiphase boride layers were determined based on the load-displacement (P-h) curves obtained in the nanoindentation tests. Three distinct regions were identified on the cross-sections of the produced layers: an outer layer consisting of MeB-type borides, an inner layer consisting of Me2B-type borides and the transition zone. The microstructural aspects of the layers were investigated using scanning electron microscopy, energy-dispersive Xray spectroscopy, and X-ray diffraction. Detailed analysis of the influence of the chemical composition on hardness, elastic modulus and fracture toughness in the three regions indicated that the most critical factor influencing the mechanical properties was the presence of chromium, iron and cobalt borides in the microstructure. Especially the formation of chromium borides reduced the fracture toughness of the transition zone.Öğe Effect of powder-pack aluminizing on microstructure and oxidation resistance of wire arc additively manufactured stainless steels(Elsevier Science Sa, 2023) Gurol, Ugur; Altinay, Yasemin; Gunen, Ali; Bolukbasi, Omer Saltuk; Kocak, Mustafa; Cam, GurelThis study investigated the effect of powder-pack aluminizing treatment on the high-temperature oxidation of ER307 stainless steel components fabricated by wire arc additive manufacturing (WAAM) during isothermal oxidation at 1000 degrees C for 5 h, 25 h, and 50 h. Scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD), X-Ray fluorescence (XRF), nanoindentation testing, and oxidation testing were used to characterize the aluminized and non-aluminized samples produced by WAAM. The results showed that the powder-pack aluminizing increased the surface nano-hardness up to 13.95 GPa and the modulus of elasticity up to 159 GPa, as well as improving the microstructure of WAAM ER307 stainless steel. Indeed, aluminide coatings remained stable up to temperatures exceeding 1000 degrees C, and the growth of hematite, the main oxide phase, was inhibited by a preferential alumina growth (Al2O3), resulting in an improvement in oxidation resistance in the range of 46-70 %. In addition, owing to the advantages of low-temperature aluminizing, the microstructure, mechanical properties, and oxidation resistance of these alloys have been improved without causing sigma phase formations, which constitute a significant problem in high-temperature heat treatment of stainless steels.Öğe The effect of process conditions in heat-assisted boronizing treatment on the tensile and bending strength characteristics of the AISI-304 austenitic stainless steel(Maik Nauka/Interperiodica/Springer, 2015) Gunen, Ali; Kurt, Bulent; Somunkiran, Ilyas; Kanca, Erdogan; Orhan, NuriIn this study, AISI 304 austenitic stainless steel surface was boronized with nanoboron and ekabor-III powders at 950 and 1000A degrees C for 2 and 4 hours period by solid-state box boronizing method. Then, behaviors of the boronized specimen in the microstructure, three-point bending, and tensile strength characteristics were investigated. As a result of the boriding process, the boride layer thickness in the range of 23-67 A mu m and microhardness value in the range of 1020-2200 HV have been obtained according to the increase in processing time and temperature and to the particle size of the boron source (0, 1). The coating layer on boronized specimens did not exhibit any sign of reaction caused by the tensile strength applied until the yield point was in both tests. Although the particle size of the boron agents was more effective on the boronized specimen's bending and tensile strength behaviors, it was observed that processing temperature and its duration are effective as well.Öğe Effect of the incorporating of refractory NbC precipitates in intermetallic iron-aluminide coatings on corrosion and high-temperature oxidation behavior(Elsevier Science Sa, 2024) Gunen, Ali; Altinay, Yasemin; Sabun, Sahin; Alkan, SabriThis study aims to investigate the effects of growing niobium carbide (NbC) particles into intermetallic iron-aluminide (FeAl) coatings on ductile cast iron (SGI) by thermo-reactive diffusion technique (TRD). The study compares the corrosion and oxidation behavior of the FeAl-NbC coatings with SGI, FeAl, and NbC coatings. Corrosion tests were conducted through polarization tests in a 3.5 wt% NaCl solution, while oxidation tests were performed at 900 degrees C for 4, 16, and 64 h. Before and after corrosion and oxidation tests, the coatings were examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The findings show that FeAl coatings with NbC particles had lower graphite nodules, porosity, and surface roughness values compared to FeAl coatings. FeAl-NbC composite coatings provided better corrosion and oxidation resistance compared to untreated SGI, FeAl, and NbC coatings. The results of the comparative analysis of FeAl-NbC, FeAl, NbC, and untreated SGI specimens indicate that corrosion resistance in a 3.5 wt% NaCl solution and oxidation resistance at 900 degrees C followed the order FeAl-NbC > FeAl > NbC > SGI.Öğe Effect of the powder particle size on the wear behavior of boronized AISI 304 stainless steel(Carl Hanser Verlag, 2015) Gunen, Ali; Kucuk, Yilmaz; Er, Yusuf; Cay, V. Veli; Oge, Mecit; Gok, M. SabriIn this study, the AISI 304 steel specimens were boronized with nanoboron of the size of 10-50 nm and commercial Ekabor 3 powders (<1400 mu m) at 950 degrees C to 1000 degrees C for 2 h and 4 h. Boronized steel specimens were characterized via SEM, microhardness and XRD analyses. Abrasive wear behavior of the specimens, boronized at different temperatures and treatment durations, were examined. The fixed ball micro-abrasion tests were carried out using the abrasive slurry, prepared with different SiC powder particle sizes on the boronized specimens at different rotational speeds. The specimens boronized with nanoboron powders exhibited a higher hardness and abrasive wear resistance than the samples boronized with the Ekabor 3 powders.Öğe Effect of thermal degradation on the properties and wear behavior of Cr-V-C composite coatings grown on ductile iron(Elsevier Science Sa, 2021) Gunen, Ali; Kanca, Erdogan; Karakas, Mustafa Serdar; Gok, Mustafa Sabri; Kalkandelen, Muge; Kurt, Bulent; Cetin, MelikThe thermal fatigue behavior of chromium vanadium carbide (Cr - V - C) coatings and the wear of the coatings after thermal fatigue cycling was studied. The Cr - V - C coatings were grown on the surface of a ductile iron using thermo-reactive diffusion (TRD) and subjected to thermal fatigue in the temperature range of 25 to 750 degrees C for up to 500 cycles. Characterizations were made using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, microhardness measurements and wear tests. The Cr - V - C coated samples displayed superior thermal fatigue and wear resistance compared to the untreated ductile iron, mainly due to the dissolution of graphite nodules in the vicinity of the surface during TRD. The dissolution of graphite reduced the possibility of failure initiating from graphite nodules and graphite-matrix interfaces. Increasing the number of cycles resulted in increased flaking and decreased wear resistance in both the Cr - V - C coatings as well as the untreated ductile iron. Although much of the Cr V C coating was lost (due to flaking) after thermal cycling, the absence of graphite near the surface still provided improved resistance to wear in the TRD-treated samples. The results of this study indicate that TRD coatings hold great promise for use in the industrial applications.Öğe The investigation of corrosion behavior of borided AISI 304 austenitic stainless steel with nanoboron powder(Maik Nauka/Interperiodica/Springer, 2014) Gunen, Ali; Kurt, Bulent; Orhan, Nuri; Kanca, ErdoganIn this study, corrosion behavior and mechanical properties of AISI 304 austenitic stainless steel, which was borided with Nanoboron powder, was investigated. The commercially available steel was subjected to a boriding treatment with a size of 10-50 nm Nanoboron powders, at the temperatures of 1223 K to 1273 K with boriding durations of 2 to 4 h. Microstructure characterization of the steel was carried out with optical microscopy, scanning electron microscopy, microhardness and X-ray diffraction analyses. Corrosion tests were made by static immersion into a 10% H2SO4 acid solution and weight loss calculations as well as salt spray tests were carried out in accord with the ASTM B-117 standard. Boriding thermal treatment, increased the corrosion resistance of the steel against the acid solution, up to about 4.3 times while in the salt spray tests, weight loss corrosion resistance increased up to tier 2. However, anti-corrosion resistance decreased by 40%, its untreated value.Öğe Mechanical Properties and Corrosion Resistance of Borosintered Distaloy Steels(Springer, 2020) Turgut, Selvin; Gunen, AliDistaloy SA is a sponge iron powder (nominal composition: Fe-1.75Ni-1.5Cu-0.5Mo) widely used in the production of powder metallurgy (P/M) parts in the automotive industry. In this study, Distaloy SA powders were sintered in two different atmospheres, one consisting of pure Ar gas (traditional sintering) and the other consisting of a mixture of 90 wt.% B4C and 10 wt.% NaBF(4)powders (borosintering). To investigate the effects of the different sintering atmospheres, the P/M samples were characterized using density measurements, surface roughness tests, scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, microhardness measurements, nanoindentation experiments, wear tests and corrosion tests. On the surface of the borosintered samples, a 160-325 mu m thick double-phase FeB + Fe2B boride layer was formed. The hardness (1405-1688 HV) and elastic modulus (122.21-162.42 GPa) of the surface were significantly improved with the borosintering treatment compared to conventional sintering (215-250 HV, 63.28-94.86 GPa). Borosintering also provided low friction coefficient values and an increased wear resistance compared to conventional sintering. A significant increase in corrosion resistance was also observed with the borosintering treatment in three different solutions. The corrosion rates of both sintered and borosintered samples were ranked as NaCl < HCl < H2SO4. The borosintered samples displayed superior corrosion resistance compared to the sintered samples, especially in the acid solutions. The results of this study show that significant cost savings can be achieved by combining the boriding and sintering treatments in a single borosintering process.Öğe Microstructural characterization and high-temperature wear behavior of refractory niobium-carbide growth in intermetallic iron-aluminide coatings(Pergamon-Elsevier Science Ltd, 2024) Gunen, Ali; Altinay, Yasemin; Sabun, SahinIron-aluminide (Fe-Al) intermetallics are characterized by their high-temperature oxidation resistance. However, their use in tribo-corrosive environments is limited due to their low hardness and brittle nature. To overcome this weakness, the feasibility of forming composite coatings (NbC-FeAl) by intercalation of refractory NbC particles into Fe-Al coatings by thermo-reactive diffusion technique and its effect on high-temperature wear behavior was investigated in this study. The coatings obtained underwent comprehensive characterization using scanning electron microscopy, X-ray diffraction, microhardness measurements, and ball-on-disc wear tests, providing valuable insights into their properties. The characterization studies showed that increasing the growth of NbC in the intermetallic iron-aluminide content resulted in a slight increase in the hardness and a decrease in the thickness of the iron-aluminide layer. Moreover, the formation of NbC in Fe-Al coatings increased the dislocation densities of the coatings, resulting in an improvement of wear resistance 2.7 times at room temperature and up to 3.5 times at 500 degrees C. While different wear mechanisms occurred in coated samples at room temperature, the dominant wear mechanism at 500 degrees C evolved into an oxidatively supported adhesive wear mechanism. This study showed that Fe-Al coatings exhibited better wear response at both room and elevated temperatures when reinforced with NbC.Öğe Microstructure, some mechanical properties and tribocorrosion wear behavior of boronized Al0.07Co1.26Cr1.80Fe1.42Mn1.35Ni1.10 high entropy alloy(Elsevier Science Sa, 2021) Karakas, Mustafa Serdar; Gunen, Ali; Carboga, Cemal; Karaca, Yusuf; Demir, Mehmet; Altinay, Yasemin; Erdogan, AzmiHigh-entropy alloys (HEAs) with face-centered cubic (FCC) structures exhibit high toughness and corrosion resistance, but their average strengths and relatively low wear resistance can limit their engineering ap-plications. In this study, FCC Al0.07Co1.26Cr1.80Fe1.42Mn1.35Ni1.10 HEAs were boronized for 4 h at temperatures of 900, 950, and 1000 degrees C to form hard, protective metal borides on their surfaces. The microstructural characteristics of the borides formed were examined using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The mechanical properties of the boride layers were studied by nanoindentation measurements, and the tribological performances of the layers were evaluated by ball-on -disk type wear tests in air, 3.5% NaCl and 5% H2SO4. Irrespective of the boronizing temperature, (Fe0.4Mn0.6) B, (Cr0.4Mn0.6)B, (CoFe)B2 and Cr2Ni3B6 phases were detected in the surfaces of the boronized samples. The surface hardnesses of the boronized samples reached nearly ten times the hardness of the as-cast HEA. The borides were effective in reducing friction as well as wear. Increasing the boronizing temperature increased the thicknesses of the coatings and further improved wear characteristics. Wear rates in 5% H2SO4 were generally higher than the wear rates in 3.5% NaCl, but the highest wear rates were observed in air. (c) 2021 Elsevier B.V. All rights reserved.Öğe Niobium Carbide Coatings Grown on Cold Work Tool Steel AISI D3 by Thermomechanical Processing: Characterization, Wear and Corrosion Behaviors(Maik Nauka/Interperiodica/Springer, 2023) Gunen, Ali; Acikgoz, Hasan Huseyin; Karahan, Ismail HakkiIn this study, niobium carbide (NbC) coatings were grown on AISI D3 cold work tool steel via thermoreactive diffusion (TRD) at 900, 1000 and 1100 degrees C for 2, 4, and 6 h. The microstructures and phase formed, the surface roughnesses, the microhardness and fracture toughness values, and the wear and electrochemical corrosion behavior of the NbC coatings were investigated. Compact, smooth and crack-free NbC layers with 8.75-17.10 mu m thickness and 1558-2286 HV0.1 hardness were obtained on the surface of the AISI D3 steel. Depending on the TRD temperature and duration, the NbC coatings improved the wear resistance by up to 5 times and corrosion resistance up to 14 times compared to the untreated alloy. With increasing temperature and duration, the thickness and microhardness values of NbC coatings increased. However, significant changes in wear and corrosion resistance was observed depending on Nb, C, O and Fe contents of NbC coatings rather than thickness and microhardness. The wear resistance was found to depend on fracture toughness as well as hardness. Corrosion resistance depended mostly on the surface roughness and the defects (especially microcracks) present on the surface.Öğe Properties and Corrosion Behavior of Chromium and Vanadium Carbide Composite Coatings Produced on Ductile Cast Iron by Thermoreactive Diffusion Technique(Asme, 2020) Gunen, Ali; Kalkandelen, Muge; Karahan, Ismail Hakki; Kurt, Bulent; Kanca, Erdogan; Gok, Mustafa Sabri; Karakas, Mustafa SerdarDuctile iron (DI) owes many of its attractive mechanical properties to the graphite nodules in its structure. However, since galvanic coupling can occur between the graphite nodules and the matrix in aggressive environments, these nodules can, at the same time, reduce its corrosion resistance. In this study, composite carbide coatings were grown on the surface of GGG-80 using the thermoreactive diffusion (TRD) process. The process was carried out at 900, 1000, and 1100 degrees C for 1 h using nanosized Fe-V and Fe-Cr powders. The coatings were characterized by X-ray diffractometry (XRD), two-dimensional profilometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and microhardness tests. The corrosion behavior of the coatings were evaluated in three different solutions (3.5 wt% NaCl, 5 wt% H2SO4, and 5 wt% HNO3) using electrochemical open-circuit potential (OCP) and potentiodynamic polarization measurements. Microstructures and hardness tests showed that the nodular graphite in the surface was dissolved at the TRD process temperatures and that a coating of 12-36 mu m thickness and 2461-3200 HV0.05 hardness was obtained. The corrosion resistance of the composite coating was up to 10, 33.5, and 75 times higher than the uncoated GGG-80 in NaCl, H2SO4, and HNO3, respectively. The improvement in corrosion resistance was a direct result of the formation of complex carbides and the elimination of graphite nodules in the surface of the alloy.Öğe Properties and Corrosion Resistance of AISI H13 Hot-Work Tool Steel with Borided B4C Powders(Korean Inst Metals Materials, 2020) Gunen, Ali; Karahan, Ismail Hakki; Karakas, Mustafa Serdar; Kurt, Bulent; Kanca, Yusuf; Cay, Vedat Veli; Yildiz, MuratIn this study, the surface of AISI H13 steel was borided with powder blends of B4C and NaBF(4)using the powder-pack method at 800, 900 and 1000 degrees C for 2, 4 and 6 h. The structural and mechanical characteristics of the boride layers formed on the surface were characterized using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, 2D surface profilometry, microhardness and electrochemical corrosion (3.5 wt% NaCl) tests. The boride layer exhibited a single phase structure (Fe2B) in samples coated at 800 degrees C and a dual-phase structure (FeB + Fe2B) at higher boriding temperatures (900 and 1000 degrees C). The boride layers were compact and crack-free in all boriding conditions. Depending on boriding parameters, the thickness, hardness and average surface roughness (R-a) of the coatings were found to range between 5.81 and 102.46 mu m, 1635-1915 HV and 0.315-0.650 mu m, respectively. The borided AISI H13 steel displayed up to 33.5 times and 2.4 times higher corrosion resistance than untreated AISI H13 steel and martensitic AISI 431 steel, respectively. This suggests potential use of borided AISI H13 steel in the steam turbines and marine applications as an alternative to the more costly martensitic and duplex stainless steel grades. The corrosion resistance depended on the phase structure (single- or dual-layer), density, thickness and surface roughness of the boride coatings. GraphicÖğe A RESPONSE SURFACE STUDY ON THE GROWN BEHAVIOR AND SOME MECHANICAL PROPERTIES OF NIOBIUM CARBIDE COATINGS(World Scientific Publ Co Pte Ltd, 2023) Gunen, Ali; Acikgoz, Hasan Huseyin; Cavdar, Faruk; Karahan, Ismail HakkiIn this study, response surface methodology was used to examine the effects of temperature and time on the development of niobium carbide coatings on AISI D3 steel. The effect of niobizing temperature (900-1100(& LCIRC;)C) and period (2-6 hours) on coating thickness, hardness, fracture toughness, coefficient of friction and wear rates was investigated. ANOVA was conducted to analyze the experimental data, and it was observed that the coating thickness and microhardness increased with temperature and time. The response surfaces developed for fracture toughness, coefficient of friction and wear rates were found to exhibit a complex structure that is significantly influenced by temperature, time and their interactions. The correlation coefficients of the developed regression models range between 0.82 and 0.99. Using the empirical formulas obtained with these mathematical models, it is predicted that niobium carbide coatings can be obtained with the targeted properties more economically and practically with the thermochemical method.
