Wear resistance of composite plasma coatings with graphite

Abstract

The wear-resistant composite solid lubricant coatings formed by atmospherec plasma spraying method of cladding Ni[Cg] powder in relation to the extreme working conditions of friction units of aircraft engines and power plants have been investigated. Examples of studies of technological processes of the plasma spraying of protective coatings on elements of liquid-propellant rocket and gas turbine engines have been given, and the possibilities of sealing technologies to increase their service life have been shown. The evaluation of efficiency of coatings obtained by plasma spraying from mechanical mixtures of powders based on Ni[Cg] in relation to power plants of vehicles based on freepiston engines.It is known that composite materials obtained by plasma spraying from the cladding by nickel powders of graphite, boron nitride BN, and calcium fluoride CaF 2 are effectively used for extreme operating conditions of friction units, seals, and structural elements of modern aircraft engines and power plants for vehicles. A comparative analysis of these materials used as the solid lubricant coatings [1] has shown that graphite-metal mixtures with a volume content of graphite within 10-35% obtained by plasma spraying from cladding Ni[Cg] powder are the most effective.The plasma coatings based on cladding nickel-graphite powder Ni[Cg] traditionally belong to the class of materials that are worn out and abradable, but resistant to erosion, oxidation, and temperature. They are used to line the inserts of the gas turbine engine stator, as well as abraded and run-in during the beginning of blade rotation, as well as sprayed on the construction elements of labyrinth seals of various types in order to ensure the minimum radial and/or axial clearance. The use of these coatings significantly reduces the leakage of air and working gas through clearances and increases the engine efficiency, but also greatly simplifies the assembly process and facilitates the repair and reinstatement of inserts and labyrinth seals.However, the use of coatings based on Ni[Cg] as antifriction coatings, which ensures the designed wear resistance in friction units, such as the sealing rings of pumps, the rotary sleeves of blades, combustion engine cylinders, and other similar friction pairs, is extremely limited. In these cases, this mean that antifriction coatings based on Ni[Cg] that work with minimal coefficients of friction prevent the seizure of metals and have lubricating ability with the minimum possible wear.In this article, the results of a study of the coatings based on Ni[Cg] powder have been proposed for use as wear-resistant solid lubricant coatings in manufacturing and repair technologies to ensure the protection of constructive units of products working under wear conditions in a wide range of temperatures and pressures. Ni[Cg] powder belongs to the class of composite cladding powders (or powders with coating). The initial materials of powder particles are as follows: the core is graphite and the cover is nickel Ni. Three types of domestic N...

Investigation of Structural and Tribological Characteristics of TiN Composite Ceramic Coatings with Pb Additives

“…An increase in the loads of thermal machines and the desire to reduce the weight of products lead to a gradual replacement of the liquid lubricants system in favor of alternative solutions. Solid lubricant coatings (SLC) can resist wear for a long time at elevated temperatures and high contact pressures [1][2][3]. Such coatings should have high wear resistance to ensure a long service life and a low friction coefficient.…”