Oxidation resistance and thermal stability of (MoZrHfTaNb)-Si-B coatings deposited by HIPIMS method with different Ar pressure

The influence of argon pressure on the structure, mechanical characteristics, oxidation resistance, and thermal stability of (MoTaNbZrHf)-Si-B coatings deposited by HIPIMS method using a composite target based on highentropy (MoZrHfTaNb)Si 2 silicide and (MoZrHfTaNb)B 2 boride was studied. Coatings deposited at Ar pressure of 0.1-0.2 and 1.3-2.2 Pa had a dense, defect-free structure. Increasing the Ar pressure to 37-42 Pa led to the formation of a coating with a columnar structure, while, according to X-ray diffraction and transmission electron microscopy, all coatings were amorphous. Increasing the Ar pressure from 0.1 to 0.2 to 37-42 Pa led to a magnifying the growth rate of coatings in 2.5 times. All coatings were characterized by a similar hardness of 14-15 GPa. The elastic modulus and elastic recovery decreased from 196 to 178 GPa and from 40 to 34 % when the argon pressure increased from 0.1 to 0.2 to 37-42 Pa, respectively. The coatings successfully resisted oxidation at temperatures of 1100 degrees C and 1300 degrees C. The protective properties of the coatings are due to the formation of a dense oxide film based on a-Si:B:O amorphous phase with crystallites of the m-HfO 2 , m-ZrO 2 , mNb 2 O 3 , o-Ta 2 O 5 , t-ZrSiO 4 and t-HfSiO 4 phases. Heating in a TEM column showed that the coating deposited at an Ar pressure of 0.1-0.2 Pa crystallizes immediately upon reaching a temperature of 700 degrees C with the release of predominantly the h-MoSi 2 phase. Crystallization of the coating obtained at an Ar pressure of 37-42 Pa also occurs at 700 degrees C, but only during long-term exposure and is accompanied by the precipitation of the h-Ta 5 Si 3 and t-Nb 5 Si 3 phases. Thus, it has been shown that by increasing the gas flow rate, the productivity of sputtering in the HIPIMS mode can be increased without a significant loss in hardness, oxidation resistance and thermal stability of coatings.