IMPACT OF CVD-PROCESS TECHNOLOGICAL MODES TO CHROMIUM COATING PROPERTIES
The present paper addresses the results of experimental investigations of producing chromium and carbide-chromium coatings by a CVD-method of organometallic compounds. The authors consider the main chemical reaction of chromium hexacarbonyl thermal decomposition and present recommendations for creating optimal conditions for its implementation. The paper presents a general view and a technological scheme of the installation producing the coatings. Particular attention is paid to the influence of the process temperature mode to the rate of coating formation and surface microhardness and a graphical dependence is shown as well. The maximum speed of coating formation is at a temperature of 300...350°C, and it is significantly reduced beyond this interval. The maximum microhardness is observed with coatings obtained on a substrate heated to 300...310°C, and a pressure of 18...19 HP. Increasing the process temperature leads to a sharp decrease of surface hardness. The paper also analyzes the influence of a metallization temperature mode on the strength of the coating-substrate adhesion. On this basis the authors conclude about the possibility of applying carbide-chromium coatings obtained in the temperature range of 300...350°C to harden the operating surfaces of farm machinery hydraulic system parts.