Influence of diode laser heat treatment and wear conditions on the fretting wear behavior of a mold steel

The effect of surface hardness on the wear loss and wear behavior during fretting was studied for a mold steel, AISI P20-improved. Moreover, the relation between the fretting wear mechanisms and conditions for fretting were investigated. A 4 kW high-power diode laser with a rectangular laser beam was used for heat treatment. The microstructural change from tempered martensite to martensite was detected for the laser heat-treated samples, which led to the increase in the hardness. As a result, a relatively lower coefficient of friction and lesser wear losses were observed for the laser heat-treated specimens in comparison to the base metal. Various tests were conducted to investigate the influence of fretting conditions on the wear behavior by varying the normal loads and frequencies. Larger normal loads led to larger amounts of wear losses, while higher frequencies led to lesser wear losses for both, the base metal and laser heat-treated specimens. Moreover, a transformation from the gross slip mode to the partial slip mode was detected from the hysteresis loops of the base metal and laser heat-treated samples with increasing normal loads and frequencies. The fretting conditions of normal loads and frequencies played a vital role in determining the fretting mode and debris retention, thereby influencing the wear loss and wear behavior.