A comparative assessment of iron and cobalt-based hard-facing alloy deformation using HR-EBSD and HR-DIC

Abstract

Three iron-based alloys (Nitronic 60, Tristelle 5183 and RR2450) and a cobalt alloy (Stellite 6) are studied using bend-testing to induce progressive straining and both high resolution DIC and EBSD are utilized to provide quantitative characterization of the deformation mechanisms. The roles of austenite, ferrite and carbide/silicide phases are investigated, together with how each contributes to slip activation and localisation, GND development and hardening through to particle pull-out and fracture. The observed mechanisms are discussed in the context of galling performance. The results suggest that a distribution of fine precipitates, both intra-granular and at grain/phase boundaries, promote more homogeneous and distributed slip, and the development of distributed higher densities of GNDs. The latter promotes hardening which in turn also facilitates homogeneity of deformation and potentially better galling resistance. A uniform size of fine precipitates is also helpful; large silicides lead to particle fracture and pull-out, likely highly damaging under conditions of sliding contact and galling.