Wear Induced Sub-surface Deformation Characteristics of a 26 Wt% Cr White Cast Iron Subjected to a Destabilization Heat Treatment

Abstract

In the present work, the sub-surface microstructure of a heat treated and worn 26 wt% Cr white cast iron was investigated to gain better insight into the tribological behaviour of the material. The samples were destabilized at 980 °C for 0 (Q_0), 30 (Q_30) and 90 (Q_90) minutes followed by air cooling, and later subjected to dry-sliding linear reciprocating wear tests. The microstructural characterization of the area under the wear track was carried out using a combination of SEM, EDS and EBSD. Additionally, nanoindentation (NI) measurements were used to corroborate the mechanical behaviour with the microstructural observations. EBSD and NI measurements indicated that the matrix area underneath the wear track in Q_0 had undergone signifcant plastic deformation resulting in a drastic increase in hardness, whereas no such phenomena was observed in the Q_90. This was attributable to the relatively high amount of retained austenite in the former and a predominately martensitic matrix in the latter. Moreover, the large M7C3 eutectic carbides were less cracked in the destabilized samples compared to the as-cast sample owing to the presence of martensite and dispersed secondary carbides, leading to an increased matrix load-bearing capacity. These factors led to the destabilized samples showing a lower wear rate compared to the as-cast sample, and the Q_0 showing the best wear resistance amongst all the samples.