Hybrid PVD-PECVD W-C:H coatings prepared by different sputtering techniques: The comparison of deposition processes, composition and properties

Abstract

The plasma polymerization processes during hybrid PVD-PECVD deposition, structure, hydrogenation, hybridization, hardness and coefficients of friction in W-C:H coatings prepared by direct current magnetron sputtering (DCMS), High Power Impulse Magnetron Sputtering (HiPIMS) and High Target Utilization Sputtering (HiTUS) were reviewed as a function of acetylene (0–12 sccm C2H2) and hydrogen (0–20 sccm H2) additions into Ar atmosphere. The addition of acetylene resulted in the increase of carbon and hydrogen contents in the matrix via incorporation of CxHy fragments with the C2H, 2C and CH radicals being the “primary” source for growth. The level of hydrogenation in the carbon matrix was found to be related to the level of sp3 hybridization and cross-linking as well. Hardness and coefficient of friction of the studied W-C:H coatings were found to be affected not only by hydrogenation and hybridization, but also by the sputtering technique. HiPIMS provided the best combination of hybridization, hydrogenation and cross-linking in the carbon structure resulting in W-C:H coatings with reasonably high (~20 GPa) hardness and simultaneously sufficiently low (≤0.1) coefficients of friction. Thus, HiPIMS applied to hybrid PVD-PECVD W-C:H coatings expands the range of their mechanical and tribological properties compared to DCMS and HiTUS.