Nano-Indentation and Tribological Studies of Ultrahigh Strength Carbon Nitride Thin Films

Carbon nitride (CNX) thin films were prepared by DC magnetron sputtering of a graphite target in a nitrogen ambient onto Si(100) and M2 steel substrates held at ambient temperatures. All CNx coatings grown to a thickness of 1.5 μm are adherent and smooth. Nanoindentation studies showed that amorphous CNx thin films have hardness and effective Young's modulus comparable to those of amorphous hard carbon. In dry sliding against 52100 steel, CNx-coated M2 substrates give initial friction coefficients ˜0.1, rising to around 0.5 in the steady state. The wear life of coated M2 steels varies inversely with normal load, rising to about two orders of magnitude higher than that of uncoated M2 at a normal load of 1.3N and a sliding speed of 0.12 m/s. This improvement is attributed to the high yield strength of carbon nitride coatings.