Development of the Chemical Vapor Deposition Process for Applying Molybdenum Coatings on the Components in Assembly and Engine Construction

Abstract

The process of chemical vapor deposition of Mo and Mo-С coatings was studied by means of thermal decomposition of molybdenum hexacarbonyl. The kinetics of the coating growth in the range of 480 °C–540 °C and the pressure in the reaction volume from 9 Pa to 16 Pa were explored. The dependences of coating growth rate, the magnitudes of their microhardness on the parameters of their obtaining, as well as the changes in the morphology of the coating surface, roughness, and structure, were established. The tribological properties of the obtained coatings coupled with bronze Br.Su3H3S20F0.2 were explored at the friction machine 2070 SMT-1 according to the "cube–roller" scheme in a load interval of 0.2–1.4 kN. The lubrication during determining the friction coefficients was carried out by immersion of the movable counter body into a bath with fuel TC-1, GOST 10227-86. It was necessary to conduct such research because there is insufficient information when it comes to the specific equipment and peculiarities of the object onto which a coating is applied. When developing the process of coating application on specific components, techniques, and means to ensure the uniformity of parts heating and precursor feeding to their surface were tested. As a result of the conducted studies, we obtained the regions of parameters of obtaining coatings with different structure, rate, hardness, as well as the patterns of changes in these characteristics at the change of the basic parameters of the process of obtaining such coatings. Depending on application conditions, coatings may have hardness from ~11,000 MPa to 18,000 MPa at a growth rate from 50 μm/h to 170 μm/h. The mean values of the friction coefficient of coatings with different microstructure and microhardness were 0.101 at the load of 0.2 kN and 0.077 at the load of 1.4 kN. Based on the conducted research, it was possible to develop the process of applying the metal and metal-carbide molybdenum-based CVD coatings in regards to the components of the assembly and engine construction, which can serve as the basis for the development of industrial technologies