Effect of Tool Wear on Rolling Contact Fatigue Performance of Superfinish Hard Machined Surfaces

This study investigates the effect of tool wear on the rolling contact fatigue performance of superfinish hard machined surfaces. Specimens were machined at two different cutting tool conditions: new and worn tools. The condition of a new tool is defined as the state of an unused tool, while that of a worn tool is defined as the state of a tool after being used for machining 150 identical specimens at the same machining conditions. It is noted that tool wear induces less compressive residual stresses for the specimens machined by square tools, while tool wear induces more compressive residual stresses in a deeper region for the specimens machined by round tools, which have a relatively large tool nose radius. In the micro-hardness distribution, the specimen machined by a worn tool typically shows a more softened layer than the specimen machined by a new tool. The rolling contact fatigue test results indicate that the rolling contact fatigue life of the specimen machined by a new tool is generally longer than that of the specimen machined by a worn tool.