Tempering Temperature Effect on Sliding Wear at High Temperatures in Mottled Cast Iron

This research analyses the effect of the microstructure of mottled cast iron on tribological behaviour using a high temperature pin-on-disc test with a steel disc oxidised at 1,200 °C ASTM A36 as a counterbody. Three different microstructures were obtained for the mottled cast iron pins by quenching and tempering at 400 °C and 600 °C. The test temperature was varied from 200 to 600 °C with the aim of approximating the temperatures reached on surface work rolls under industrial conditions. The oxidation of the ASTM A36 disc at 1,200 °C was used to reproduce a counterbody (calamine) similar to that occurring in the hot roll mill steel under industrial conditions. The other tribological test parameters were held constant (normal load of 20 N and sliding speed of 0.05 m/s). The experimental results at the lowest test temperature (200 °C) show that the wear strongly depends on the microstructure and that the greatest friction coefficients are present at this condition. However, at higher test temperatures (400 and 600 °C), the wear resistance depends on the pin oxide stability. The highest wear rate occurs at a test temperature of 400 °C, and the lowest wear rate occurs at 600 °C. The explanations for these phenomena are discussed.