Nanostructured Tungsten-Based Composite Coatings and Their Applications

The object of the paper is the further investigation of unique superhard (35−40 GPa) nanocrystalline (nc) coatings based on W3C phase, which is chemically vapor deposited at low temperature 400−700 °C and atmospheric pressure from the mixture of WF6 + C3H8 + H2 with the following partial pressure ratios:  WF6/H2 = 0.04−0.09 and C3H8/H2 = 0.15−0.5. Propane must be preliminarily subjected to catalytic cracking at 560−570 °C for 10−150 s in the presence of a stainless steel surface. The novel W3C phase (A15 with ao = 0.5041 nm) is different from well-known WC and W2C by its associated lattice and Vickers microhardness (HV0.5N) of 35−40 GPa. Deposits have shown that they are a mixture of both the W3C phase and α- and β-carbynes, which are chainlike carbon structures (−C⋮C−)n/(CC)n. Nanocrystalline structure of the nc-W3C/nc-carbyne composite with a nanocluster size of 2−100 nm, which is typical for the majority of novel superhard coatings, was discovered. It was shown that the nc-W3C/nc-carbyne composite coat...