THE FAILURE MODELS INDUCED BY WHITE LAYERS DURING IMPACT-WEAR

The characteristics of impact wear of high hardness steel have been st udied by repetitive impact testing. The subsurface microstructure and wear debris have been investigated, and both wear resistance and failu re models are discussed. Experimental results indicate that there are two zones beneath the worn surface (WS): namely a white layer (WL) and a deformation zone (DZ). The WL is an intensely deformed layer. Micro cracks which form originally in this WL ultimately cause the failure o f the steel samples. Based on the experiment, two failure models relat ed to the WL are proposed. (1) Delamination occurs when microcracks pr opagate along the path parallel to the WS. (2) Spalling occurs when mi crocracks propagate along the flow lines in the DZ.