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In the present study, the wear properties of 205 manganese steels produced by a casting process with different boron contents (0.0023-0.0182 wt.%) were investigated, using a pin-on-disc tribometer under dry sliding conditions. The friction coefficient of 205 manganese steel by boron addition (at 0.0076 wt.%) reduced from 0.28 to 0.18. The addition of boron to 205 manganese steel led to a decrease in the friction coefficient due to the lubricating effect of boron. X-ray diffraction showed that the boron addition to 205 manganese steel increased lattice parameters of the samples. The wear test results at 5 and 10 N loads showed that the wear amount of 205 manganese steels decreased with boron addition. Thus, the wear results showed that the wear resistance of 205 manganese steel is increased with the addition of small amounts of boron. Furthermore, scanning electron microscopy images indicated that the characteristic wear mechanisms for the boron-doped samples on the worn surfaces were abrasive, and it was plastic deformation, mild abrasive, and adhesive wear mechanism in the undoped 205 manganese steel.

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.

TiC coatings on AISI D3 cold-work tool steel were carried out by pack method thermo-reactive diffusion process (TRD) for 2 and 4 h at 950, 1 000, 1 050 and 1 100 °C, respectively. The carbide layers were evaluated based on microstructure, thickness, hardness, energy dispersive X-ray facility and X-ray diffraction analysis. Titanium carbide layer thickness on the coated specimens ranged from 6 to 23 μm, depending on treatment time and temperature. Growth kinetics of the carbide layers were analyzed measuring the depth of carbide layer as a function of temperature and time. The activation energy was estimated to be 249.42 kJ/mol. The micro-hardness value of the coating layer was obtained to be 2 470 HV in maximum.

In this study, Co-Cr-Mo powder was coated on the surface of AISI 304 stainless steel by the plasma transfer arc (PTA) process at 80, 90 and 100 A current values and argon gas was used for both plasma and protective. Deposition layers were examined with optical microscopy, SEM, EDX, XRD analysis and microhardness test. The thickness of the coating increased with current density. No cracks or pores were detected in the interface and coating layer. Higher current levels resulted in higher dilution levels and also in melting/burning of the substrate.

Porous NiTi shape memory alloy (SMA) was fabricated by self-propagating high-temperature synthesis (SHS). With this study, a new solution treatment “solution treatment under loading” was applied to porous NiTi SMA fabricated by SHS to determine microstructural improvement regarding single phase NiTi. The effect of solution treatment under load on chemical composition, constituent phases and phase transformation behaviors of the specimens was investigated and discussed. The chemical composition of the specimens considerably changed with solution treatment under loading. Intermetallic phases such as Ti 2 Ni and Ni 4 Ti 3 disappeared, the density of B2(NiTi) phase increased and phase transformation temperatures sharply decreased. Porous single phase B2(NiTi) SMA with high chemical homogeneity could be obtained by the load applied during solution treatment at 1050 °C.

In this study, the Ti–6Al–4V alloy was diffusion bonded to austenitic stainless steel at temperatures of 820, 885, 930 and 980°C, under a pressure of 5 MPa for 30 min. The effect of temperature on interface formations and microstructure was investigated using a scanning electron microscope (SEM), energy dispersive spectrograph (EDS) microanalyses, X-ray diffraction and shear strength of bonded specimens. The results showed that intermetallic phases and σ-phase formed in the interface region.

Porous NiTi shape memory alloy was fabricated by self-propagating high temperature synthesis. Effects of solution treatment under load applied on the microstructure were investigated. The densities of the phases changed insignificantly with solution treatment but the intermetallic phases such as Ti2Ni, Ni4Ti3 and Ni3Ti2 disappeared and the density of B2(NiTi) phase increased with the load applied during solution treatment. Consequently, porous NiTi SMA with ideal pore characteristics, high chemical homogeneity and high strength for hard tissue implants was obtained.

In the present study, Ti-6Al-4V alloy was diffusion bonded to a ferritic stainless steel. The effect of bonding temperature on the microstructural development across the joint region was investigated. After diffusion bonding, microstructural analysis including metallographic examination, energy dispersive spectrograph (EDS) and shear strength was conduced. From the results, it was seen that bonding on the temperature was affecting the Fe and Ti mutual diffusion which controls the interface microstructure. The microstructure of the interface region was formed, consisting of Fe and Ti intermetallics. (c) 2006 Elsevier B.V. All rights reserved.

In the present study, a high chromium white iron was diffusion bonded to a low carbon steel. The effects of bonding temperature and holding time at the reached temperature on microstructural developments across the joint region were investigated. After diffusion bonding, microstructural analysis including metallographical examination, energy dispersive X-ray (EDX), wavelength dispersive X-ray (WDX), microhardness measurements and shear strength tests were performed. The results showed that bonding temperature with holding time was effective on the width of the diffusion zone that affected the shear strength of the bonds. As a result, from the microstructural observations, EDX and WDX analysis, microhardness measurements and shear strength tests, it was concluded that a high temperature with a long holding time must be used in the diffusion bonding of high chromium white cast irons to low carbon steels.

In this study, porous Ni–Ti and Co–Cr–Mo alloy couple was fabricated by powder metallurgy (PM) process. With this aim, Ni–Ti and Co–Cr–Mo alloys powder was compacted into the mould one by one with Co–Cr–Mo being the one side and Ni–Ti the other side. Then, Ni–Ti side of the specimen was synthesised by self-propagating high temperature synthesis (SHS) process. At the end of the SHS process (after the SHS process), the porous Ni–Ti alloy has occurred. Finally, the specimen was sintered at 1050°C into argon atmosphere. Scanning electron microscope with energy dispersive X-ray spectroscopy and X-ray diffractometer were used to characterise the microstructure and composition. It was seen from the results that porous Ni–Ti and Co–Cr–Mo alloy couple was successfully fabricated by PM process.

Thermal reactive diffusion (TRD) coating on a DIN 1.2367 die steel substrate was performed in a powder mixture consisting of ferrovanadium, ferrochromium, ammonium chloride, alumina, and naphthalene at temperatures of 1000, 1050, and 1100°C for 2–4 h. The carbide layers were characterized using the microstructure, microhardness, X-ray diffraction, and chemical analysis. Wear scars were analyzed on scanning electron microscopy (SEM) micrographs with an energy-dispersive X-ray spectroscopy module. Depending on the coating process time and temperature, the thicknesses of the vanadium carbide and the chromium carbide layers formed on the substrate were obtained in a range from 7 to 30 μm and 5 to 17 μm, respectively. The maximum hardness values of vanadium carbide and chromium carbide layers were measured as 2537 and 1973 HV, respectively. The test samples coated using the TRD method were analyzed with regard to abrasive wear behavior using three different loads (1, 2, and 3 N) and speeds of 40, 80, and 160 r...

In the present study, VC coatings on AISI D3 steel were processed by pack method thermo-reactive diffusion method (TRD) in a solid medium for 2 and 4 h at 950, 1000, 1050 and 1100 °C, respectively. Then, the coated specimens were characterized by scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray diffraction analysis. From the results, between 5.6 and 26.8 μm carbide layers on the surface were obtained by increasing process time and temperature. The coatings were determined by VC and V2C phases. The kinetics of vanadium carbide coating was also studied and the activation energy was estimated to be 180.73 kJ/mol. The avarage value of the microhardness of the coating is 2400 HV. The ball crater test was applied to determine the micro abrasion behaviors of the coated samples.

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...

In this study, the characterization and growth kinetics of chromium carbide layer coated on AISI D3 cold-work tool steel by pack method thermo-reactive diffusion process in solid medium were carried out. Coatings were performed by using ferro-chromium powder as Cr source at 950, 1 000, 1 050 and 1 100 °C for 2 and 4 h. The carbide layers were evaluated based on microstructure, thickness, hardness, energy dispersive X-ray facility and X-ray diffraction analysis. Chromium carbide layer thickness on the coated specimens has been in the 4.2–17 μm range depending on treatment time and temperature. Growth kinetics of the carbide layers were analyzed by measuring the depth of carbide layer as a function of temperature and time. The activation energy was estimated to be 180.13 kJ/mol. The microhardness values of the coating layers are range of 1 200–1 600 HV. Ball rotating micro-abrasion technique was used to carry out wear tests on the thin coating layers.

Diffusion bonding of duplex stainless steel to medium carbon steel was carried out with different temperatures for sound bonds. in the bonding process, relatively intermediate temperatures such as 750, 800, 850 and 900 degrees C were used with a bonding time of 30 min. In this study, microstructural changes and mechanical properties in the interface region of duplex stainless steel and medium carbon steel couples were determined. The results showed that, in interface region, Cr(23)C(6) was formed on the stainless steel side, while ferrite formation was observed on the carbon steel side as a result of mutual diffusion of C and Cr. (C) 2009 Elsevier Inc. All rights reserved.