Plasma carburization of wear-resistant high chromium iron

Abstract

A series of 10–34 wt.% Cr alloyed iron (2 wt.% C) prepared by a spray-forming process (the Osprey process) were plasma carburized. The plasma carburization was performed for 2–9 h and 1–3 h at 950 °C and 1040 °C respectively, in a CH 4 gas atmosphere to keep the surface carbon content sufficiently high to form carbide dispersion layers, without subsequent diffusion treatment. Evaluation of these layers was conducted by X-ray diffraction, electron probe microanalysis, optical microscopy, microhardness measurements and wear testing. In typical results of 26 wt.% Cr iron, owing to an increase in fine chromium carbide precipitation during carburization, the surface Vickers hardness reached over 1000 HV and the surface carbon content amounted to about 5 wt.%. The wear loss in the severe sliding wear condition performed by an Ogoshi-type wear test decreased to a quarter of that of uncarburized material. These characteristic values varied according to the chromium content. Further, we discuss the types and quantity of carbides identified by X-ray diffraction methods.