Tribological behavior of selected M_n+1AX_n phase thin films on silicon substrates

In the last years, M_n+1AX_n (MAX) phases came into the focus of functional thin film research. Potential fields of application for MAX phases are structural materials for high temperatures, tribological protective coatings, electrical contacts in aggressive environments, and as sensing materials in sensor technology.This paper focuses on the tribological behavior of Ti₃SiC₂, Ti₂AlN and Cr₂AlC phase thin films against a counterpart bearing steel 1.3505. The MAX films are deposited by magnetron sputtering of elemental multilayers and a rapid thermal annealing synthesis. The formation of the MAX phases is investigated by X-ray diffraction and transmission electron microscopy. The reciprocating micro-tribological sliding against steel balls, scanning electron microscopy and energy dispersive X-ray spectroscopy revealed an adhesive wear mechanism for Cr₂AlC and Ti₂AlN with friction coefficients in the range of 0.30 to 0.70 and 0.15 to 0.50, respectively. The best friction and wear behavior were observed for Ti₃SiC₂ with a friction coefficient in the range of 0.15 to 0.25. Furthermore, for all MAX phases, hypotheses for the wear mechanisms are formulated.