In this study, the surface of AZ91 magnesium alloy plasma sprayed with WC-12 wt-%Co powder was melted by pulsed Nd:YAG laser. Microstructure, chemical composition and phase analyses of the treated layers were studied by utilising a scanning electron microscope equipped with energy dispersive spectroscopy, X-ray diffraction technique and a microhardness testing machine. Laser treated layers showed much finer structure compared to that of the original base material with suitable distribution of WC particles. Microhardness of melted zone achieved at optimum condition was ,3.5 times higher than that of the base material. In addition, the presence of WC particle and refined structure reduced the wear rate to less than half in the laser treated layer.
In this paper, liquid phase surface engineering of Ti-6Al-4V titanium alloy using a 400 W average powerpulsed mode Nd:YAG laser has been studied. Optimized parameters of the laser treatment were determined based on the quality and properties of the fabricated surface layers. Optical microscope and scanning electron microscope equipped with EDS analyzer were used to investigate the microstructural and geometrical features of the laser-treated surfaces. In addition, x-ray diffraction method was also applied for phase analysis of the treated layers. The microstructures of the melted zones were mainly consisted of a¢ martensite together with Ti 3 Al intermetallics where a¢ martensite had hexagonal structure with acicular morphology. a¢ martensite transformed to fine a + b structure after tempering at 480°C for 7 h. Microhardness measurements showed approximately two-fold increases in hardness after surface melting (600-630 HV 0.2 ) compared to that of the parent metal (300-350 HV 0.2 ).
Solid state carbothermic reduction of tungsten oxide (WO3) to nanosized tungsten carbide (WC) particles was achieved by heating mechanically activated mixture of tungsten oxide and graphite at different temperatures under vacuum condition. KCl and Ni were added to the mixture for some samples. The morphology and chemical composition of products, as well as particles size and their distribution were compared by X-ray diffraction and field emission scanning electron microscopy. Mechanical activation of WO3-C powder mixture did not yield WC phase whereas it was possible to produce WC nanoparticles by heating at 1250 °C for 2 h. KCl additive caused fine and homogeneous particle and Ni additive assisted the growth of WC particles.
In the present work Ti-6Al-4V titanium wrought alloy was initially sprayed with TiC-15 wt% Ni powder, before being liquid phase surface treated by pulse Nd-YAG laser. Microstructure, chemical composition and phase analysis and hardness of the treated layers were studied by using field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), X-ray diffraction analysis (XRD) and micro-hardness test respectively. The result showed that the treated layers had ultrafined dendritic structure containing nanosize TiC particles and their hardness were as high as 982 HV0.03respect to 350 HV0.03for the base material.
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