Electron Microscopy Analysis on the Worn Surface of a High-Chromium White Iron During Dry Sliding Contact

Abstract

ABSTRACTA series of microstructural phenomena within a thickness of material (tribolayer) below the worn surface, have been developed during dry sliding wear of a high-chromium cast iron. The overall wear behavior of the alloy is determined by the properties of this tribolayer. From the present work, a transmission electron microscopy analysis has been undertaken on the different features developing at different distances below the worn surface following wear sliding tests of a 17%Cr white cast iron alloy, whose microstructure is composed by 25% eutectic M7C3 carbides within an austenitic matrix. The observed phenomena is an increase in the dislocation density, plastic deformation by twinning followed by severe shear banding along with carbides fracture, a mechanical mixture formed by iron oxide and carbide particles produced from large carbides comminution, and finally a flat iron oxide layer. Wear debris was apparently created from the oxide film detaching from the outermost surface where equivalent strain is maximum. No evidence of strain induced martensite was observed from the present work, which has been reported in some austenitic materials. The implications of the microstructural evolution are discussed in terms of the wear theories and behavior of metals at high strains levels.