Investigations were conducted on the microstructure and behaviors of abrasive wear and impact wear of 16%Cr-3%Mo white cast iron without and with 2.7%Nb-1%V addition heat-treated at 1253K followed by forced-air cooling to clarify the difference between two kinds of wear mechanisms. Microstructures were analyzed by means of scanning electron microscope equipped with energy dispersive X-ray spectrometer, X-ray diffractometer and ferrite meter. Results reveals that since MC spheroidal carbides are formed by addition of Nb and V, the other primary carbides are refined and martensite in the matrix becomes more stable. Such microstructure improves abrasive wear resistance, but deteriorates impact wear resistance. Under the severe test condition, self-tempering softening of martensite in the matrix caused by the impact energy of abrasive media and it increases the impact wear rate.

  The role of retained austenite and martensite on impact-wear resistance of 27%Cr cast iron quenched at temperatures of 1223K and 1423K was investigated at various impact angles by impact wear tests using an air blasting machine. Measurement of the hardness and volume fraction of martensite in the matrix of both samples as well as SEM observation were performed. Quenching treatment at 1223 K resulted in a higher volume of initial martensite in the matrix, and wear rate reached maximum at 60°. On the contrary, the matrix with a high volume of retained austenite obtained by quenching at 1423K showed maximum impact-wear rate at 45°. The difference in the wear resistance between the two types of as-quenched samples can be explained by the transformation from metastable austenite to work-induced martensite and self-tempering of the initial martensite occurring under impact wear environment. As the volume of retained austenite increases, hardening due to work-induced martensite was found to overlap with softening due to tempering of the initial martensite, which contributed to the suppression of the wear rate.