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This study focused on chromium addition (0 wt%, 3 wt%, 6 wt%, 9 wt% and 12 wt%) on the boride layer formation, microhardness, fracture toughness and elevated temperature friction and wear behaviour of alloys formed by powder metallurgy (P/M). The boride layers obtained on P/M alloys were characterized by examining density, porosity, surface roughness, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray difraction, surface proflometry, microhardness, and fracture toughness. The addition of Cr has a signifcant efect on both boride layer formation and friction-wear behaviour of P/M alloys. Increasing the Cr addition up to 6 wt% has an improving efect on the microhardness, fracture toughness and wear resistance of the P/M alloys, whereas in the case of 9–12 wt% Cr addition causes exfoliation in the boride layer and low fracture toughness, thus reducing wear resistance. Coefcients of friction and wear volume losses at elevated temperatures are higher than room temperature. The best wear resistance at room temperature was obtained in the sample containing 3 wt% Cr with the highest fracture toughness, while the best wear resistance at 250 °C and 500 °C was obtained in the sample containing 6 wt% Cr, where the highest hardness value was obtained.

Distaloy 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.

In this study, Ni-based Inconel 718 coatings were additively manufactured on the surface of AISI H13 work tool steel by electro-spark deposition (ESD). Some of the electro-spark deposited samples were boronized at 1000 ? for 5 h to evaluate the effects of boronizing on microstructure, high-temperature wear, and corrosion resistance. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), 2D pro-filometry, wear and electrochemical corrosion testing was used to characterize the surfaces, microstructures, microhardness, some mechanical properties, high-temperature wear, and corrosion resistance of the applied coatings. Wear tests were performed at room temperature and 650 ?, and corrosion tests were performed in 3.5% NaCl at room temperature, considering the applications of AISI H13 and Inconel 718 alloys. The characterization studies showed evidence of microcracking and oxidation in the as-deposited Inconel 178 coatings. In the boronized Inconel 718 coatings, the oxides and microcracks were slightly reduced. The hardness of the boronized Inconel 718 coating was increased to about four times the hardness of the as-deposited Inconel 718 coating, and this significantly improved its wear resistance. The highest wear resistance was achieved with the boronized coating, while the best corrosion resistance was obtained with the as-deposited coating. The improvements in wear resistance provided by boronizing have the potential for expanding the applications of Inconel 718 coatings in machine components.

WOS: 000520134000010, Remelted NiCrBSi coatings were examined using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction analysis, microhardness and wear testing. After wear tests, the surfaces of the worn samples were examined by 3D profilometry and scanning electron microscopy to investigate the effects of load and temperature on the coefficient of friction and wear resistance. In all the wear experiments, there was a momentary increase in the wear volume and a momentary decrease in the average coefficient of friction values at the elevated test temperatures. This behavior was caused by the stable oxide layer formed on the surface as a consequence of the elevated test temperature. Three dominant wear mechanisms were observed with the NiCrBSi coatings: delamination at room temperature, spalling and adhesion at 250 degrees C, and oxidation at 450 degrees C, whereas in the uncoated samples there was delamination at room temperature, and micro-cracking and oxidation, both at 250 degrees C and 450 degrees C. Remelted NiCrBSi coatings provided better wear resistance and lower coefficient of friction than uncoated STKM-13A steel, especially at higher temperatures.

In this study, titanium carbide (TiC) coatings were grown on the surface of a spheroidal graphite cast iron (SGI) via thermo-reactive diffusion (TRD) using powder-pack processing at 800 °C, 850 °C and 900 °C for 4 h. The TiC coatings obtained on the SGI were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), surface profilometry, microhardness, VDI adhesion testing, wear testing, and electrochemical corrosion testing. Depending on the TRD temperature, continuous, crack-free, and smooth TiC coatings of 5–11 μm thickness and 27.96–32.45 GPa hardness were obtained on the surface. The high chemical stability, high hardness, and good adhesion strength of TiC coatings resulted in a reduced friction, high wear resistance, and superior corrosion resistance compared to the untreated sample. Delamination and oxidation assisted abrasive wear transformed into oxidation-assisted adhesive wear in the coated samples. Galvanic corrosion was dominant in untreated SGI, while homogeneous corrosion occurred in the coated samples. TiC coatings grown using TRD have the potential to be used in engineering components exposed to tribo-corrosive conditions.

CoCrFeNiAl0.25Ti0.5 high entropy alloy alloys (HEA), produced by powder metallurgy were subjected to boriding to improve their mechanical properties. Sintering was carried out at 1200 degrees C for 2 h in Ar, and boriding was performed at 900, 1000 and 1100 degrees C for 2 h using a 90 wt% B4C + 10 wt% NaBF4 boriding powder mixture. Microstructures, densities, surface roughnesses, and mechanical properties (hardness, fracture toughness and nanoindentation responses) of the samples were investigated. FCC, BCC and sigma phases had been observed after sintering, whereas complex metal borides were formed on the surfaces after boriding. Relative density values were between 85% and 90%. Significant increases in surface hardness were observed after boriding due to formation of hard, silicide-free boride layers. The boride layer thickness and hardness increased with increasing boriding temperature. The elastic modulus of the surface of the sintered sample (47.07 GPa) increased with the boriding process to values in the range of 140-151 GPa. Fracture toughness values between 3.57 and 4.25 MPa m(1/2) were obtained in borided samples, and increasing the boriding temperature reduced the fracture toughness.

High-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.

WOS: 000525414900007, In the present study, Ramor 500 armor steel plates were automatically welded using cold metal transfer arc welding (CMT), gas metal arc welding (GMAW), and hybrid plasma arc welding (HPAW) methods. To investigate the effects of three different fusion welding methods on metallurgical and mechanical properties, the welded joints were examined using optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) and also subjected to radiographic, hardness, tensile, and notched impact tests. The weld metal (WM) region of the GMAW and HPAW joints consisted of massive austenite. In the CMT welded joint, the WM consisted mainly of dendritic austenite and a minor amount of delta-ferrite. Regardless of the welding process, the hardness of both the WM and heat-affected zone (HAZ) regions was found to be higher than the base metal (BM). The tensile strengths obtained by CMT, GMAW, and HPAW were 45%, 50%, and 65% of the BM, respectively. Cleavage-type brittle fractures occurred in the GMAW and HPAW welded joints, while localized ductile fractures occurred in the CMT joints. Tensile test specimens of the CMT joints fractured in the WM, while the GMAW and HPAW joints fractured in the HAZ. In terms of notch toughness, the CMT joints exhibited better impact resistance compared with the BM. GMAW and HPAW joints displayed less impact resistance than the BM, with values comparable with previous studies in the literature.

In this study, the surface of AISI H13 steel was borided with powder blends of B4C and NaBF4 using the powder-pack method at 800, 900 and 1000 °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 °C and a dual-phase structure (FeB + Fe2B) at higher boriding temperatures (900 and 1000 °C). The boride layers were compact and crack-free in all boriding conditions. Depending on boriding parameters, the thickness, hardness and average surface roughness (Ra) of the coatings were found to range between 5.81 and 102.46 µm, 1635–1915 HV and 0.315–0.650 µm, 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. Graphic Abstract: [Figure not available: see fulltext.]. © 2019, The Korean Institute of Metals and Materials.

Ductile 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 °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 µm 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.

WOS: 000511876700037, Silicide-free boride layers were grown on Inconel 718 Ni-based superalloy surface at 850 degrees C, 950 degrees C, and 1050 degrees C for 2, 4, 6 hour by the powder pack-boronizing process using nano-sized B4C powders. The coatings were examined using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, 3D profilometry, and microhardness measurements. Wear experiments were carried out on untreated and boronized Inconel 718 using a ball-on-disk tribometer under dry sliding conditions at temperatures of 25 degrees C, 400 degrees C, and 750 degrees C. An increase in boronizing temperature and duration increased the thickness and hardness of the obtained boride layers, which resulted in low coefficient of friction values and decreased wear rates. Scanning electron microscopy images of the worn surfaces revealed two-body abrasion as the effective wear mechanism in the untreated samples, and three-body abrasion assisted by microcracking and spalling as the dominant wear mechanism in the boronized samples. A transition from mild to severe wear occurred in the untreated samples, while wear rates remained low in the boronized samples up to 750 degrees C. In conclusion, boronized Inconel 718 was capable of sustaining its boride layers under 5 N for 1800 m at wear-test temperatures up to 750 degrees C.

WOS: 000526984400027, In this study, sintering and boriding methods are applied as a single step, and it is aimed to gain time and economic advantage. For this purpose, powder mixtures prepared in suitable compositions were subjected to sintering and boro-sintering processes. In the boro-sintering process, the sintering was carried out in the boriding atmosphere and the two processes were carried out together. The processing, microstructure, hardness and dry sliding wear behavior of the samples were studied. The powders were pressed under different pressures, and their effects on the properties of the final component were investigated. The sintering process was carried out for 2 h at 1000 degrees C, and the boro-sintering process was carried out at 1000 degrees C for 2, 4 and 6 h. Fe2B and Fe2B + FeB boride phases occurred depending on the boro-sintering process duration. Boride layer thickness varied between 120 and 400 mu m according to boro-sintering duration and cold press pressure. Vickers micro-hardness and Ball-on-disc wear tests were performed on the samples. Whereas 205-215 HV hardnesses were obtained in the sintered samples, 1252-1705 HV hardness values were reached by boro-sintering process. Increased cold pressing pressure reduced wear losses. However, the long boro-sintering time increased surface hardness, but reduced wear resistance., Scientific Research Funds of Bartin University [2018-FEN-A-023], This work was supported by Scientific Research Funds of Bartin University (Project Number: 2018-FEN-A-023).

WOS: 000396779900008, In this study, the surface of steel tooth drill bits (Ni-Cr-Mo based) was subjected to the solid-state boriding treatment with 10- to 50-nm nanoboron powder. Boriding processes were carried out at a constant temperature of 1273 K for 30, 45, 60, 75, 90, and 105 min using a solid-state box boriding technique. Borided drill bit samples were characterized by conventional methods (microstructure, microhardness, X-ray diffraction, and chemical analysis). The wear behavior of borided samples was tested at different loads and sliding speeds by a microabrasion experimental setup. Metallographic studies showed that the boride layers have a sawtooth morphology and consist of FeB and Fe2B. The thickness and hardness of the boride layer were 35.29-202.56 mu m and 1300-2333 HV0.1, respectively, depending on the duration. The wear resistance of borided samples increased significantly due to the increase in surface hardness and lubricating effect, both of which were caused by the boriding process. A groove wear mechanism prevailed in borided samples, whereas that of bare steel tooth drill bits (STDBs) was grooving, rolling, and mixed., TUBITAK Council [213M629], This study was supported by the TUBITAK Council (Project No. 213M629).

WOS: 000465193500040, In the current study, the surface of AISI D2 steel was coated with the powder blends of ferro-vanadium (Fe-V) and ferro-chromium (Fe-Cr). The coatings were performed using a thermo-reactive diffusion (TRD) treatment by the pack cementation method at three different temperatures (900 degrees C, 1000 degrees C, and 1100 degrees C) and three different durations (1 h, 2 h, and 3 h). The structural and mechanical characteristics of the coatings were compared between the treatment groups. For this aim, the types of the formed phases, the microstructure, the microhardness, the surface roughness, and the wear and friction performance of the coated samples were examined. XRD analysis found composite carbide coatings including chromium carbide (Cr-C), vanadium carbide (V-C), and chromium vanadium carbide (Cr-V-C). The coatings' thickness was 11.3-23.2 mu m, hardness was 2100-2500 HV, and average surface roughness (R-a) was 0.286-0.550 mu m, depending on the treatment condition. The vanadium containing phase contents of the coatings increased with the elevating coating temperatures. The formed composite coating layers caused a change in the appearance of wear track and wear mechanism on the material surface. After the coating process, there found to be a decrease in the friction coefficient as well as an improvement in the wear resistance up to 7 times. In the composite coating layers, the increase in V-C content in comparison to Cr-C led to an enhancement in wear resistance on the material surface.

WOS: 000526980900010, A two-step Thermo reactive diffusion processes (including an initial titatinizing step followed by boronizing) is proposed in order to obtain superhard complex TiBC coating layer on AISI D6 steel. Microstructural characterization and mechanical properties of obtained TiBC layer conducted by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), optical microscopy, 2D profilometer, X-ray diffraction (XRD), micro-hardness, nano-indentation hardness and ball-on disc wear tests. Wear tests were carried out in ball on disc device by applying 30 N load and 500 m sliding distance against WC abrasive ball. Microstructural studies revealed a compact, homogenous and crack-free TiBC layer with 0.29-1.91 surface roughness (Ra), 3.65-29.5 mu m thickness and 1800-4841 HV0.05, hardness and 146-235 GPa elastic modulus. Hardness values of TiBC layers was significantly higher than those obtained by standard titanizing and boronizing due to the interspersed TiB and TiC phases within the TiBC layer. Higher hardness values are highly effective on the wear resistance and wear type. Thus, in parallel with the increase in mechanical properties, wear resistance increased in the range of 4-120 times in comparison with the untreated AISI D6 sample. Severe wear and extensive plastic deformation was observed in the untreated AISI D6, while micro-cutting, micro-cracking and pitting was dominant in samples with hardness 1800-4000 HV. When the surface hardness reached values above 4000 HV the wear mechanism further changed to microcracking and spalling.

WOS: 000437057900015, Externally cooled rolls of a steel plant were coated using three different surface modification techniques, namely titanizing, boronizing and borotitanizing. The grown coatings were examined using optical microscopy, scanning electron microscopy, microhardness measurements, X-ray diffraction and Raman analysis. Depending on the coating technique, a wide range of coating thicknesses and microhardness values were obtained; the highest microhardness was obtained in the titanized sample, while the greatest coating thickness was obtained in the borotitanized sample. Wear tests were performed on the untreated and coated specimens using a ball-on-disc wear tester under two different loads (1 N, 3 N) at three different temperatures (25 degrees C, 25 degrees C, 45 degrees C). The average friction coefficient values decreased at elevated temperatures, and increased under increased load. Temperature had a significant effect on the wear mechanism. At room temperature the effective wear mechanism was delamination, while at 25 degrees C and 45 degrees C oxidative wear was observed. All of the surface modification treatments improved the wear resistance. The highest wear resistance was observed in the borotitanized sample.

In this study, AISI 304 austenitic stainless steel surface was boronized with nanoboron and ekabor-III powders at 950 and 1000°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 µm 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.

WOS: 000404484300001, Science Citation Index Expanded, The Ni-based superalloy Inconel 625 is extensively used owing to its high strength, excellent fabricability, good weldability and outstanding resistance to high temperature corrosion against aggressive environments. However, despite its unique properties and extensive use, its wear resistance is in some cases unsatisfactory. In this study, Inconel 625 was subjected to boriding treatments at different temperature and different durations. Microstructural characterization was made by conventional methods (scanning electron microscopy, optic microscopy, X-ray diffraction analysis) and mechanical characterization was made by microhardness and micro-abrasion wear test. Micro-abrasion wear tests were conducted against a AISI 52100 steel under 5, 7.5 and 10 N load in a 25 wt.% SiC slurry at room temperature. Microstructural results revealed that multi-phase boride layer (nickel boride, chrome boride and iron boride) and silicide layer were formed. The hardness and thickness of the boride layers were found to be 1175-2432 HV0.1 and, 6.61 - 92.03 mu m, respectively. Depending on the boriding temperature and time. In spite of silicide layer formation the wear resistance of borided Inconel 625 alloy increased up to 8 times thanks to the increase in the surface hardness which was caused by boriding process. The boriding treatment caused a transition in the wear mechanism. While grooving was observed in the untreated Inconel 625 samples, mixed (grooving and rolling) and rolling type wear was predominant in the borided samples., Mustafa Kemal University Research Council [13911]; Mustafa Kemal University Research Council, This study was supported by the Mustafa Kemal University Research Council (Project Number 13911). The authors wish to thank Mustafa Kemal University Research Council for its grant contributions to this study.

In 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.

WOS: 000443177400014, In this study, Inconel 625 Ni-based superalloy, widely used in industrial application, was bonded with three different bonding powders. The bonding powders used were as follows: the first one consists of 90% elemental nanoboron and 10% NaBF4, (NB), the second one consisting of 90% nano hexagonal boron nitride and 10% NaBF4(h-NBN), and the third one being commercial EKabor 2 powder. Bonding is conducted at 1000 degrees C for 180 minutes. Then the bonded samples were investigated with optical microscopy, microhardness test and X-Ray Diffraction (XRD) analysis. In these investigations, the effect of bonding powders with different chemical content on the properties of the coating layer and the phase formation was examined. As a result of these examinations it was observed that boride, silicide and nitride coating layers were obtained depending on the chemical content of bonding powder. The fact that the boron phases with higher boron contents were obtained with nano boron powder indicate that the degree of purity of boron powder has an effect on the type of phases to be formed. In this study, undesirable silicide layer formation encountered in Ni-based super alloys was prevented by changing the chemical composition of bonding powders. Furthermore, nano boron and hexagonal boron nitride powders, have been developed as alternative boron powders to commercial EKabor-Ni bonding powder as well as thicker coating layers have been obtained by using these newly developed bonding powders than commercial boron powders (Ekabor Z Ekabor-Ni and B4C).

WOS: 000395355300044, Inconel 625, a nickel-based superalloy, is used in a wide range of applications including the marine and petroleum industries under where it is subjected to harsh conditions such as high temperatures and highly corrosive environments. However, its wear resistance is limited and can be often considered unsatisfactory in some applications. If this alloy were to be used under abrasive wear conditions, its surface would have to be protected by a wear resistant coating. In this study, a two-step thermo-chemical borotitanizing treatment (including an initial boriding step followed by titanium diffusion) is proposed. Microstructural characterization (optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction) and mechanical properties (induding micro-hardness and micro-abrasion wear) of the coated samples were conducted. Microstructural studies revealed a compact, homogenous, silicide-free coating, consisting of four distinct regions: a TiB2 layer, a multi-phase boride layer, a diffusion zone and the substrate. Hardness values were significantly higher than those obtained by standard boriding treatments. Due to the nano-sized bodding agents used, the coatings formed on the surface were thicker than coatings obtained by methods such as nitriding, paste bodding and pack-boriding, and comparable to that of laser boriding. The wear resistance was improved by up to ten times in comparison with untreated Inconel 625. Grooving was the effective wear mechanism in untreated Inconel 625. How-ever the increase in surface hardness achieved by the borotitanizing treatment changed the wear mechanism in the coated samples from grooving to rolling. (C) 2016 Elsevier B.V. All rights reserved., Scientific Research Council of Mustafa Kemal University [13911], This study was supported by the Scientific Research Council of Mustafa Kemal University (Project Number 13911). The authors wish to thank Mustafa Kemal University for its grant contributions to this study.

In this study, 304 stainless steel was boronized using nano boron powders using a solid-state box boronizing technique. Boronizing processes were carried out at temperatures of 950 and 1000°C for 2 and 4 h of treatment. Nano boron was used as a source of boron and KBF4 salt was used as an activator. The boxes in which boron was processed were made of 304 stainless steel plates. A free-ball microabrasion test was performed on the boronized samples. Silicon carbide (SiC) abrasive powders (5 μm) were used in the abrasion experiments. The ball rotational speed was 73.7, 102.5, and 147.4 rpm in the free-ball microabrasion test. Boronized steels showed an improvement in abrasive wear resistance. Microstructures and wear surfaces of the samples were inspected using scanning electron microscopy (SEM) and optical microscopy. It was observed from SEM and optical examinations that boronizing time and temperature had an important effect on the thickness of the boride layer on steel surfaces. The presence of boride fo...