Synthesis and friction behavior of chemically vapor deposited composite coatings containing discrete titanium nitride and MoS sub 2 phases

Composite coatings containing discrete crystalline phases of titanium nitride and MoS sub 2 were deposited on Si, graphite, and Ti-6Al-4V alloy substrates by simultaneous chemical vapor deposition. MoF sub 6 and H sub 2 S were utilized as the precursors for MoS sub 2 formation, while Ti((CH sub 3 ) sub 2 N) sub 4 and NH sub 3 were used for titanium nitride deposition. The composition and microstructure of the coatings were investigated by x-ray diffraction, Auger electron spectroscopy, and transmission electron microscopy. The molar ratios of titanium nitride and MoS sub 2 in the composite microstructure could be controlled by adjusting the MoF sub 6 concentration in the reagent mixture. Encouraging friction and wear characteristics against silicon nitride were obtained for a composite coating which was rich in MoS sub 2 at the coating surface, with titanium nitride as the major phase near the substrate interface. Friction coefficients at room temperature in air were typically in the range of 0.07-0.3. The friction coefficients remained comparable at 573K, but increased to 0.7-1.0 at 673K. A friction coefficient value of approx0.3 was, however, obtained from a composite coating tested at 973K.