Galling Resistant Surfaces on Stainless Steel Through Electrospark Alloying

Abstract

Galling is a severe type of wear usually occurring at high normal stress and small relative movement between contacting surfaces. Surface protrusions, plastic deformation, magnified increases in roughness, and final seizure of the coupled pair characterize galling. Austenitic stainless steels are particularly prone to this surface disruption and a number of processes have been used to reduce or eliminate this extreme form of adhesion. In this study 316 stainless steel surfaces are treated by means of the microwelding process electrospark alloying (ESA). A variety of electrode compositions ranging from very hard (WC) to very soft (Ag) were used in both self mated and single surfaced tests. A standard gall test supplemented by a recording torque wrench was used for evaluation of surfaces. Tests were run at normal stresses of 35.1, 123, and 211 MPa. While all the compositions evaluated eliminated galling some showed abrasive cutting and the rotational torque requirements were high. Cobalt used in a self mated couple and silver used in a single surfaced couple were found to be the superior electrode materials for eliminating galling tendencies of 316 stainless steel.