Solid lubricant ceramic coatings on aluminium and its alloys

Abstract

Intensive development of space technology, chemical and electronic industries, modern machine-building industries requires creation of antifriction materials with significantly higher tribotechnical properties. Ceramic materials based on aluminium oxide and formed in a microarc discharge plasma on the surfaces of aluminium parts are very promising. However they can not work in friction nodes without lubrication and intensive cooling. Their antifriction properties might be improved by including micro-and nanoscale particles of an antifriction filler in a ceramic matrix to obtain ceramic coatings with solid lubricant properties. The authors consider the basics of the original microarc technology that makes it possible to obtain new composite solid lubricating coatings, which consist of various aluminium oxides, as well as solid lubricant dispersed inclusions, such as graphite, molybdenum disulphide and magnetite. They also analyse the effect of inclusion of highly dispersed filler particles from a colloidal electrolyte on the coating formation process. In order to improve the quality of coatings, it is suggested to use filler particles coated with solvated shells. An electrochemical installation for obtaining a composite coating has been improved to create an increased concentration of dispersed phase particles in the coated sample surface area. The paper investigates tribotechnical properties of the obtained wear-resistant oxide coatings on an aluminium alloy. It is shown that the inclusion of special dispersed particles in its composition can ensure a stable and continuous operation of a friction unit, reduction of a friction coefficient and linear wear under conditions of lubricant deficit. A ceramic coating with a molybdenum disulphide has shown the highest antifriction characteristics.