SURFACE REMELTING OF NI-CR-B-SI CLADDING WITH A MICRO-BEAM PLASMA-ARC

A new method of surface modification, micro-beam plasma are melting/re melting, is proposed in order to improve the corrosion and wear resist ance of materials. This process was applied to Ni-Cr-B-Si overlays pro duced by a plasma transferred are process. The microstructure in the r emelted layer of overlay was examined by optical microscopy and scanni ng electron microscopy. The effects of remelting on both corrosion and abrasion resistance were investigated by electrochemical measurement in 1N H2SO4 aqueous solution and a pin-on-disc abrasive wear test, res pectively. The results show that the dendritic microstructure of the N i-Cr-B-Si overlay was much refined in the plasma-arc-remelting layer a nd even equiaxed microcrystallites may be obtained with 2 A are curren t and 90 mm min(-1) scanning velocity owing to the self-quenching effe ct of the substrate. Because of the solute-trapping and the refinement of microstructure, both corrosion resistance and abrasion resistance of Ni Cr B Si overlay can be enhanced by the micro-beam plasma are tre atment. (C) 1997 Elsevier Science S.A.