Hardening the surface of metals with WC1-x coatings deposited by high-speed plasma spraying

The deposition of protective hardening coatings allows increasing the lifetime of important technical materials and pure metals. This work shows the possibility of depositing protective coatings based on cubic tungsten carbide (WC1-x) on metal substrates using a high-speed (~1 km/s) plasma jet generated by a coaxial magneto-plasma accelerator. In a plasma spraying process, the necessary conditions (high sputtering and crystallization rates) are created for synthesizing the high-temperature WC1-x phase and stabilizing it in the coating structure. The formation of WC1-x phase was confirmed by X-ray diffraction and energy dispersive X-ray spectroscopy. The substrate parameters such as linear dimensions and heat dissipation rate were found to directly affect the phase composition (WC1-x yield) and the structure of the deposited coating. The coatings with a higher WC1-x content are characterized by an increased hardness. The firstly made direct measurements of a Berkovich hardness (H = 33.0 ± 0.9 GPa) and Young's modulus (E = 401 ± 14 GPa) for bulk WC1-x grains, exceeding several micrometers in size, confirmed the suggestion about higher mechanical properties of the metastable WC1-x phase in comparison with hexagonal tungsten carbides WC and W2C. •WC1-x-based coatings were successfully deposited on copper by plasma spraying.•WC1-x phase purity in the coating structure depends on heat dissipation rate.•At optimal conditions, the content of WC1-x phase can reach up to 99 wt%.•A Berkovich hardness of WC1-x is 33.0 ± 0.9 GPa and Young's modulus is 401 ± 14 GPa.