Improved High-Temperature Softening Resistance and Wear Resistance of AISI M42 High-Speed Steel by N-Alloying

Herein, a novel high-nitrogen (0.18 wt%) M42 high-speed steel is fabricated by pressurized metallurgy. The high-temperature softening resistance of N-free and 0.18N steels is evaluated by hardness measurement at room temperature after additional heating at 600 degrees C for various times, and the high-temperature wear resistance is evaluated by ball-on-disk dry sliding wear test at 600 degrees C. The microstructure is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscope (HRTEM). The results indicate that the hardness of 0.18N steel is 2-3 HRC higher than that of N-free steel after additional heating at 600 degrees C for 4-120 h. The superior high-temperature softening resistance of 0.18N steel is primarily ascribed to the smaller coarsening rate of M2C secondary carbides. Under the dry sliding condition at 600 degrees C, the wear rate of N-free steel is approximately 1.5 times higher than that of 0.18N steel. The better high-temperature wear resistance of 0.18N steel is primarily because the superior softening resistance makes it maintain higher hardness during the wear process to provide stronger support for the oxide layer and increase the protective ability of oxide layer to steel.