Optimization of pyrolytic chromium carbide coating properties

Abstract

The paper discusses ways to optimize the properties of pyrolytic chromium carbide coatings (PCCC) for different industries. PCCC applications include protecting surfaces of different parts and units made of various materials against corrosion, sticking, high temperatures, and various types of wear. Such versatility of PCCCs is explained partly by the peculiarities of their structure that is generally a «superlattice» of alternating relatively hard and soft layers of different composition and, accordingly, functional characteristics such as microhardness and Young modulus. These structures with specific periods and layer thickness ratios correspond to the maximum quality criterion of the optimal control theory (OCT) problem, an inverse problem stated on the class of solutions for a direct problem simulating specific interaction, e.g. abrasive wear. At the same time, the direct problem itself, e.g. an indentation description, is an incorrect inverse problem of mathematical physics, and it needs its own optimal strategy to be solved. This results in a hierarchy of optimization algorithms that can be used to obtain best PCCC functional properties. When an abrasive-wear type direct problem cannot be formalized, it is suggested to use a computational-experimental method elaborated by the authors that is also based on OCT. The main focus is on the improvement of the PCCC deposition technology for every specific application using the optimal control theory. To obtain PCCCs that meet these conditions, it is required to take into account the physical and chemical features of precursor pyrolysis as well as the effect of different additives or catalysts in the process development.