Plasma surface alloying of spheroidal graphite iron

Spheroidal graphite iron is chosen as a substrate material on which plasma W-Mo and Ni-Cr surface alloying are carried out by the Xu-Tec process. The experimental results show that W-Mo surface alloying increases the surface hardness of the cast iron from approximately 200 to 1500 HV while Ni-Cr all oying enhances the surface hardness to 600 HV or above and also the corrosi on-resistance of the cast iron. The alloy content and hardness of the alloy ed layer manifest a gradually decreasing tendency from surface to the insid e of the substrate, an ideal profile which is beneficial to the cohesion of the surface modification layer with the bulk material. The microstructures , alloy contents and surface hardnesses of the alloyed layers are presented . Effects of processing conditions and carbon, silicon content of the speci mens on the alloying results are also discussed. (C) 2000 Published by Else vier Science B.V. All rights reserved.