An investigation was carried out to examine the effect of austempering on the microstructure and mechanical properties of nodular cast iron GGG 50 (DIN EN 1563) alloyed with different amount of copper. Optical, scanning electron microscopy and energy dispersive spectroscopy analyses were performed for microstructural characterization. In addition, hardness and tensile tests were carried out for mechanical properties determination. Specimens were austenitized at 900°C for an hour, then austempered for an hour at 330°C in salt bath and cooled at a room temperature in air. The results indicated that the addition of Cu to GGG 50 encouraged pearlite formation in the matrix structure. In addition, with the austempering heat treatment, the structure was transformed from ferrite + pearlite into ausferrite and retain austenite. Furthermore, for the alloy with 2 wt% Cu addition, it was noted that the graphite nodules diverged from sphericity and Cu was concentrated around the graphite. After austempering, mechanical properties were significantly improved and the highest mechanical properties were found at 1.5 wt% Cu.
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.
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.
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.
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