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EN
In this study, the corrosion behaviors of nitride and titanium aluminum nitride (TiAlN) layers deposited on AISI D2 steel samples are reported. Steel was at first nitrided in a nitrogen and ammonia atmosphere at 575C for 8 h and then titanium nitride coating treatment was performed in the powder mixture consisting of ferro-titanium, aluminum, ammonium chloride and alumina at 1000C for 2 h by thermo-reactive diffusion technique. Phase analysis and corrosion tests were realized on the titanium aluminum nitride coated steel. The corrosion properties of uncoated and coated samples were characterized by potentiostatic polarization test. The tests were conducted using a three-electrode system test unit with a platinum counter electrode of 2.269 cm^2 and an Ag/AgCl, 3 M KCl electrode as the reference electrode. Nitrided and TiAlN coated steel specimens exhibited higher corrosion resistance than uncoated steel in 0.5 M H_2SO_4 solution. Conclusively, the application of nitride and TiAlN films on AISI D2 steel increased surface hardness and corrosion resistance. TiAlN coating exhibits the highest corrosion resistance.
EN
In the present work, the corrosion behavior of Cr-Al-N coating formed on the pre-nitrided AISI D2 cold work tool steel by thermo-reactive diffusion technique in the powder mixture consisting of ferro-chromium, aluminum, ammonium chloride and alumina at 1000C for 2 h was investigated. The phases formed in the coating layers were Cr_2N, (Cr,Fe)_2N_{1-x}, AlN, and Fe_2N which were confirmed by X-ray diffraction analysis. The uncoated, nitrided, and Cr-Al-N coated specimens were placed in corrosive media (3.5 wt% salt solution). A standard saturated calomel electrode was used as a reference and graphite as a counter or auxiliary electrode. The effectiveness of the coatings in preventing corrosion was tested in the NaCl solution by electrochemical impedance studies using the Nyquist plots and potentiodynamic studies as well. Conclusively, the application of nitride and Cr-Al-N layers on AISI D2 steel increased its surface hardness and corrosion resistance. The corrosion resistance of Cr-Al-N coatings is higher than that of uncoated and nitrided steels.
EN
In this study, chromium aluminum nitride coating was applied on pre-nitrided AISI D2 steel by the thermo-reactive deposition technique in a powder mixture consisting of ferrochromium, aluminum, ammonium chloride, and alumina at 1000C for 2 h. Steels were gas nitrided for the purpose to enrich the surfaces with nitrogen of the steels in a nitrogen and ammonia atmosphere at 560C for 8 h. The effect of aluminum content in the powder mixture on the Cr-Al-N layer properties was investigated. The coated samples were characterized by X-ray diffraction analysis, scanning electron microscope, and micro-hardness tests. Chromium aluminum nitride layer formed on the pre-nitrided AISI D2 steel was compact and homogeneous. Electron dispersive spectrometer results showed that coating layer includes chromium, aluminum, and nitrogen. X-ray studies showed that the phases formed in the coating layers on the steel surfaces are Cr_2N, (Cr,Fe)_2N_{1-x}, AlN, and Fe_2N. The depth of the Cr-Al-N layer ranged from 10.01 ± 1.2 to 13.2 ± 1.7 μm, depending on the aluminum content. The hardness of the coated layers produced on AISI D2 steel are changing from 1743 ± 150 HV_{0.01} to 2067 ± 160 HV_{0.01} depending on bath compositions.
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vol. 125
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issue 2
584-586
EN
It is now well established that considerable improvement in the mechanical/chemical properties of near surface regions of materials can be achieved by the process of surface alloying. In the present study, surface alloying treatment with molybdenum and boron on the surface of the AISI 1020 steel was realized by the technique of tungsten inert gas welding. Ferrous boron alloy and ferrous molybdenum were used for surface alloying treatment. Before the treatment, ferrous alloys were grinded and sieved to be smaller than 45 μm. Prepared powder was pressed on the steel substrate and melted by tungsten inert gas welding for surface alloying. Coated layers formed on the steel substrate were investigated using optical and scanning electron microscopy, X-ray diffraction analysis and Vickers microhardness testers. It was shown that surface alloyed layer has composite structure including steel matrix and well distributed boride phases. Borides formed in the coated layers have a small precipitated structure and distributed in the grain boundaries as continuous phases. X-ray diffraction analyses show that coated layers include Fe_2B, Fe_{13}Mo_2B_5, Mo_2FeB_4, and iron.
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vol. 125
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issue 2
587-589
EN
Surface alloying caused the improvement in the mechanical/chemical properties of near surface regions of the steels. In the present study, surface alloying treatment with boron, molybdenum, and iron on the AISI 1020 steel was realized by the technique of TIG welding. Ferrous boron, ferrous molybdenum, and Armco iron were used for surface alloying treatment. Before the treatment, ferrous alloys were ground and sieved to be smaller than 45 μm. The powders were mixed to be composed of Fe_{(15-x)}Mo_{x}B_5, where x = 1, 3, and 5 (by at.%). Prepared powders were pressed on the steel substrate and melted by TIG welding for surface alloying. Wear tests of the surface alloyed AISI 1020 steels were realized against WC-Co ball using by ball-on-disk method under the loads of 2.5, 5, and 10 N at the sliding speeds of 0.1 m/s for 250 m sliding distance. Friction coefficient and wear rates of the surface alloyed steel with Fe_{(15-x)}Mo_{x}B_5 alloy powder are changing between 0.30 and 0.80 and 5.86 × 10^{-5} mm^3/m to 2.52 × 10^{-3} mm^3/m depending on applied load and alloy composition, respectively.
EN
Thermo-reactive diffusion/deposition technique is an alternative to physical vapor deposition and chemical vapor deposition techniques for obtaining wear and corrosion resistant coatings on steel parts. In this work, thermo-reactive diffusion/deposition technique was used to produce niobium aluminum carbonitride-based coatings on AISI M2 steel. Characterization of the coatings was done by X-ray diffraction analysis, scanning electron microscopy and energy dispersive spectroscopy. The corrosion resistance of the produced coatings was investigated by using potentiodynamic polarization in a solution of 0.5 M NaCl. Hard, compact and adherent coatings, mainly consisting of NbC and NbN phases were obtained. The corrosion behavior of the samples was investigation by potentiodynamic polarization measurements.
EN
In this study, aluminum-doped (1 and 2 wt.%) and Al-free niobium carbo-nitride coatings were applied to the surface of AISI M2 high speed steel using the process of thermo-reactive deposition technique (TRD) at 1000°C during 1-4 h. The obtained coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis and micro hardness test. Nb-Al-C-N layers were compact and homogeneous. X-ray diffraction analysis has shown that the major phases formed in the coating layer are Nb₂CN and NbN. The depth of the coating layer had increased with the treatment time and ranged from 6.65 to 9.05 μm. The measured values of the hardness of the coating layers were ranging between 2136 and 2636 HK_{0.005}.
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vol. 125
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issue 2
362-364
EN
The wear properties of uncoated, chromium aluminum nitride (CrAlN) and titanium aluminum nitride (TiAlN) coated AISI D2 steel were investigated and compared using ball-on-disc method at 0.3 m/s sliding speed and under the loads of 2.5 N, 5 N, and 10 N against Si_3N_4 ball as a counter material. Steel samples were nitrided at 575C for 8 h in the first step of the coating process, and then titanium aluminum nitride coating and chromium aluminum nitride were performed by thermoreactive deposition (TRD) process at 1000C for 2 h. Coated samples were characterized by X-ray diffraction analysis, scanning electron microscopy, microhardness, and ball on disk wear tests. The results of friction coefficient and wear rate of the tested materials showed that the TiAlN coating presents the lowest results.
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vol. 125
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issue 2
359-361
EN
In the present study, the corrosion behaviors of chromium aluminum nitride (CrAlN) and titanium aluminum nitride (TiAlN) coatings deposited on AISI D2 steel samples are reported. Steel samples were pre-nitrided at 575C for 8 h in the first step of the coating process, and then TiAlN and CrAlN coatings were performed by thermoreactive deposition process in a powder mixture consisting of alumina, ammonium chloride, aluminum and ferrous titanium or ferrous chromium for TiAlN or CrAlN, respectively. Coating treatments were realized at 1000C for 2 h. Coated samples were characterized by X-ray diffraction analysis, optical microscopy, scanning electron microscopy, and microhardness tester. The corrosion properties of uncoated and coated samples were characterized by potentiostatic polarization test. CrAlN and TiAlN coated steel specimens exhibited the higher corrosion resistance than uncoated steels in a 0.5 M NaCl solution.
EN
Ba(Ti_{1-x}Zr_{x})O₃ (x=0÷0.3) ceramics were prepared by the standard solid state reaction method and were sintered at 1450°C for 4 h. The structural and dielectric properties of the samples were studied. The phases formed in the ZrO₂ doped BaTiO₃ were tetragonal and of cubic symmetry. Increase in ZrO₂ content in the BaTiO₃ caused to increase of the lattice parameter and crystallite size of the perovskite structure. The evolution of the Raman spectra was studied for various compositions and the spectroscopic signature of the corresponding phase was determined. The scanning electron microscope was used to investigate the microstructure and surface morphology of the sintered samples. Scanning electron microscope observations revealed enhanced microstructural uniformity and retarded grain growth with increase of ZrO₂ content. Dielectric characteristics of ZrO₂ doped barium titanate were studied using a Hioki 3532-50 LCR meter in the frequency range of 1 kHz-1 MHz. It is found that the dielectric constant (ε_{r}) increases while the dielectric loss (tan δ) decreases with increase in zirconium oxide content (x<0.3).
EN
In the present study, AISI 1020 plain carbon steel was surface alloyed with preplaced 50%Fe-10%W-40%B alloying powders using a tungsten-inert gas (TIG) heat source. Microstructure, hardness, and wear resistance of the surface alloyed layer were investigated. Following the surface alloying, conventional characterization techniques such as optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction analysis (XRD) were used to study the phase and microstructural examinations of the alloyed surfaces. Hardness measurements were performed across the alloyed zones, and wear properties of the alloyed surfaces were evaluated using a ball-on-disc wear test method. Hardness values of the phases formed in the alloyed layer are changing between 620±30 HV_{0.1} and 2095±254 HV_{0.1}. The major phases formed in the surface alloyed layer were Fe₂B, FeB and FeW₂B₂. Wear test were realized against Alumina ball under the loads of 2.5 N, 5 N and 10 N at the sliding speed of 0.1 m/s for 250 m sliding distance. The friction coefficient of the 50%Fe-10%W-40%B alloyed steel surface is changing between 0.70 and 0.79 depending on applied loads. The wear rates of the surface alloyed steel ranged from 4.01×10^{-5} mm³/m to 4.14×10^{-4} mm³/m.
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vol. 125
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issue 2
251-253
EN
It is now well known that surface alloying caused improvement in the mechanical/chemical properties of near surface regions of materials. In the present study, surface alloying treatment with boron, vanadium and iron on the AISI 1020 steel was realized by the technique of TIG welding. Ferrous boron, ferrous vanadium and Armco iron were used for surface alloying treatment. Before the treatment, ferrous alloys were ground and sieved to be smaller than 38 μm. The powders were mixed to be composed of Fe_{15 - x}V_{x}B_5, where x = 1, 3, and 5 (by at.). Prepared powders were pressed on the steel substrate and melted by TIG welding for surface alloying. Coated layers formed on the steel substrate were investigated using scanning electron microscopy, X-ray diffraction analysis and Vickers microhardness testers. It was shown that the surface alloyed layer has a composite structure including steel matrix and eutectic borides. Wear tests of the surface alloyed AISI 1020 steels were realized against WC-Co ball using ball-on-disk method.
EN
In this study the effect of H₃BO₃ on the properties of Ni-B coating formed on the AISI 1020 steel surface produced with electroplating process was investigated. Synthesis of the coatings was done using acidic electro plating bath. Coating process was carried out within a standard cell with three electrode system using platinum as auxiliary and Ag/AgCl electrode as a reference electrode onto AISI 1020 steel substrate. Then, heat treatment was applied to coatings at 400°C during a period of 1 h. The coated samples were analyzed by optical microscope, scanning electron microscope, and X-ray diffraction. Micro hardness measurements of the coatings were realized. The study reveals that the Ni-B anti corrosion coating is amorphous in their as-plated condition and upon heat treatment at 400°C for 1 h, Ni-B coatings crystallize and produce nickel borides and nickel in the coatings. The results indicated the presence of Ni₂B, Ni₃B and Ni phases.
14
Content available remote

Characterization of Fe-Nb-B Base Hardfacing of Steel

88%
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vol. 125
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issue 2
656-658
EN
Recently hardfacing by welding has become a commonly used technique for improvement of material performance in extreme (high temperature, impact/abrasion, erosion, etc.) conditions. In the present study, three different alloy compositions of the Fe-Nb-B were used for hardfacing of the AISI 1020 steel by tungsten inert gas welding process and analyzed. The coatings were produced from a mixture of ferrous niobium, ferrous boron and iron powders in the range of - 45 μm particle size with different ratio. The coatings' thickness was set to 2-3 mm on the substrate. Microstructure, phase analysis and hardness of the manufactured hardfacing alloys were characterized. Deposition results indicate good quality thick coating and porosity free of the hardfacings. X-ray diffraction analyses showed that the alloyed layers include iron borides, FeNbB and iron phases. It was shown that surface alloyed layer has composite structure including steel matrix and well distributed boride phases.
EN
In the present study, the production of Inconel 718 nickel based superalloy was carried out in an electric current activated sintering in open air under a uniaxial pressure of 300 MPa using Al, Ni, Fe, Cr, Ti, Co, Fe-Nb and Fe-Mo powders. This alloy was heat treated, following the conventional treatment which consists of a 1 h solution treated at 980°C, followed by air cooling and double ageing, 8 h at 720°C, furnace cooling at 55°C/h down to 620°C and ageing for 8 h. Optical and SEM examinations showed a dense microstructure with low amount of porosity. XRD studies showed the existence of the γ and MC type carbide (M atom is a Nb, Ti combination) and δ phases. The relative density of sample measured according to Archimedes' principle was 93.7%, and the microhardness of sample was about 343.8 HV_{0.1}.
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88%
EN
In this study, boro-titanizing treatment was applied to AISI 1040 steel. In the coating treatment, steel samples were pre-boronized in a slurry salt bath consisting of borax, boric acid and ferro-silicon at 900°C for 2 h, then titanized by thermo-reactive deposition technique (TRD) in a powder mixture consisting of ferro-titanium, ammonium chloride, alumina and naphthalene at 1000°C for 1-4 h. The coated samples were characterized by X-ray diffraction analysis (XRD), scanning electron microscope (SEM), glow discharge optical emission spectroscopy (GDOES) and micro-hardness tests. Coated layer formed on the pre-boronized AISI 1040 steel was compact and homogeneous. X-ray studies showed that the phases formed on the steel surfaces are TiB₂, TiC, TiN and Fe₂B. The depth of the coating layer ranged from 3.41± 0.47 μm to 6.59± 0.51 μm, depending on treatment time. A higher treatment time resulted in a thicker boro-titanized layer. The average hardness of the coating layer was 4527± 284 HV_{0.005}.
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