Авіаційно-космічна техніка та технологія (Apr 2018)
POTENTIAL APPLICATION OF COLD GAS-DYNAMIC SPRAYING OF PROTECTIVE AND RESTORATIVE COATINGS ONTO MAGNESIUM PARTS
Abstract
Magnesium alloys are widely used in modern technology, especially in the aviation and automotive industries, primarily due to low density, which allows reducing the weight of products and structures significantly. However, one of the main disadvantages of magnesium alloys is low corrosion resistance, which limits the possibilities of their wide application. A large number of magnesium parts of helicopters are prone to corrosion in places of contact with parts made of other metals forming a galvanic couple. Moreover, magnesium alloys are also susceptible to surface damage due to impact, which often occurs in the manufacture, repair and maintenance of aviation equipment. Scratches and damage can lead to local corrosion. It is shown that energy- and resource-saving cold spraying technology is effective and advanced technology for repairing and recovering of magnesium parts against corrosion. The cold gas-dynamic spraying technology is a relatively new industry among the processes of thermal spraying. The cold spray process is based on accelerating the metal powder particles with a supersonic gas stream in the Laval nozzle followed by an impact on the substrate and the formation of a coating. The process is characterized in that the powder material used in the spraying process does not melt and therefore the oxidation of the coating decreases; there are no phase changes in the material and no considerable heating of the substrate. The results of the analysis of the current state of cold spraying of protective and restorative coatings as well as the analysis of the aviation engines magnesium parts manufactured by «MOTOR SICH», their damages, in particular corrosion, causes of occurrence and current protection methods are accomplished. The works aimed to deposition of cold spray corrosion-resistant coatings and its application for restoration and protection of magnesium parts against corrosion are analyzed. The previous work in the field of cold spraying of anticorrosive coatings was mainly aimed to achieving maximum density of coatings, since the absence of through porosity provides reliable protection of the base material. Coatings with a minimum porosity were obtained using the high-pressure cold spray systems. The analysis showed that the issue of using low-pressure cold-spray equipment remains open and confirms the urgency of further research
Keywords
