Wear behavior under high temperature and lubrication condition of Fe-based alloy coating formed by laser cladding

In order to increase the wear resistance of 40Cr steel, Fe-based alloy coating was obtained on the surface of 40Cr steel substrate with preset laser cladding technique. The microhardness of both clad coating and substrate were measured by microhardness tester, and the micrographs of clad coating were scanned by SEM. Moreover, wear tests were carried out by wear tester to determine the rule of friction coefficient varying with temperature under lubrication condition. As the tests show, good metallurgical bonding was obtained between Fe-based alloy coating and 40Cr substrate. The microstructure of cross section of the clad coating presents a vertical distribution of planar crystal, dendrite crystal and cellular crystal. The microhardness value of the clad coating fluctuated between 617.5 and 926.6 HV0.2, while that of substrate between 205.2 and 278.2 HV0.2. Below 200 °C, the wear process of clad coating kept stable. The average friction coefficient of clad coating kept at 0.1. As the temperature exceeded 200 °C, the lubrication oil film decomposed and led to lubrication failure, the wear mechanism gradually transformed from micro-scale abrasive wear to adhesion wear, abrasive wear and oxidation wear.