Effect of loads on wear behavior of carbon steel surface with gradient microstructure at high temperature

•The high temperature wear behavior of carbon steel with gradient microstructure is analyzed under different loads.•The gradient microstructure can improve high temperature wear resistance.•The wear mechanisms change from oxidation wear to adhesive wear, and finally to severe delamination. The present research investigated the effect of loads on high-temperature wear behavior of carbon steel with gradient microstructure. The results demonstrated that the gradient grain refinement was obtained, with grain size ranging from 0.1 to 3 μm. An increase in the coefficient of friction and wear volume was observed with the load increased. The wear mechanism of the sample changed from oxidation wear to delamination wear, with the load increased from 15 N to 75 N. Moreover, under low loads, it was found that a continuous oxide film was formed on the gradient surface, which retained the favorable high temperature wear properties. However, under high loads, the gradient layer was completely penetrated, and the low binding strength between the oxide film and the matrix resulted in the initiation and propagation of cracks, thereby exhibiting a poor wear performance of the sample.