Laser-fabricated Fe-Ni-Co-Cr-B austenitic alloy on steels. Part I. Microstructures and cavitation erosion behaviour

Laser surface alloying using NiCoCrB alloy (Ni-17.1% Co-19.6% Cr-14.5% Fe-3 .5% B-1% C-0.9% Si) on mild steel AISI 1050 and austenitic stainless steel AISI 316L was attempted. Both steels alloyed with NiCoCrB contained austeni te as the main phase, with carbides and borides as the minor phases. The ma ximum hardness of laser-alloyed 1050 and 316L increased to 545 and 410 Hv, respectively, with the cobalt content ranging from 4.5 to 12 wt.%. The cavi tation erosion resistance R-e in deionized water was determined by an ultra sonic vibration system. R-e was found to increase with the Co content in th e alloyed layer, reaching a value 4.4- and 12-fold that of the substrate fo r 1050 and 316L, respectively. The increase in R-e was attributed to a decr ease in the stacking-fault energy and enhancement of strain-induced martens itic transformability due to the presence of Co. Increase in hardness due t o the presence of carbides and borides and a refined microstructure resulti ng from laser treatment also contributed to an enhanced resistance. (C) 200 1 Elsevier Science B.V. All rights reserved.