| It was investigated the influence of process variables, such as time, temperature, pressure and current density on the hardness, microstructure and surface carbon content during plasma carburizing of a low carbon Cr-Mo steel(0.176C, 0.119Si, 1.014Cr, 0.387Mo). As the process variables increased, the effective case depth in plasma carburized steel increased up to 50% in comparison to that of gas carburizing. With increasing time, cementite formed along the austenite grain boundaries at carburized surface and thickened. Also the surface carbon content increased initially, then its rate slowed down. Owing to the enhanced carbon adsorption rate on the surface during plasma carburizing, the supersaturation of austenite with respect to carbon occurred faster than in conventional gas carburizing process. The effective case depth increased with the surface carbon content. It is considered that the formation of carburized layer of low carbon Cr-Mo steel during plasma carburizing depends on the surface carbon content so that the use of plasma would not influence the diffusion rate of carbon in steel. |
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