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 - and -carbynes, which are chainlike carbon structures (-CC-)n/(=C=C=)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 coatings have significant potential for industrial applications.