Thermal stability of nanostructured Cr3C2-NiCr coatings

The thermal stability behavior of nanostructured Cr3C2-NiCr coatings was investigated. The nanostructured Cr3C2-NiCr coatings, synthesized using mechanical milling and high-velocity oxygen fuel (HVOF) thermal spraying, were thermally exposed in air at 473, 673, 873, and 1073 K for 8 h, The results show that microhardness of the conventional coating increased slightly with increasing temperature, while that of the nanostructured coating drastically increased from 1020 to 1240 HV300 for the same temperature increases. Heat treatment led to increases in scratch resistance and decreases in the coefficient of friction for the nanostructured Cr3C2-NiCr coatings. A high density of Cr2O3 oxide particles with average size of 8.3 nm was found in the nanostructured coatings exposed to high temperatures, which is thought to be responsible for the observed increase in microhardness and scratch resistance and the decrease in the coefficient of friction of the nanostructured coatings.