SURFACE REPAIR OF AIRCRAFT TITANIUM ALLOY PARTS BY COLD SPRAYING TECHNOLOGY

Abstract

Titanium alloys have the advantages of high specific strength, good corrosion resistance, high heat resistance, and low density, which is the main structural material of aerospace system components, including compressor blade, cartridge receiver, blisk, engine nacelle, thermal baffle and so on. At present, about three-quarters of titanium and titanium alloys in the world are used in the aerospace industry, including A350 for 14%, F18 for 15 %, B787 for 15 %, SU-57 for 18 %, J-20 for 20 %, FC-31 fighters for 25 %, F35 for about 27 %, and F22 up to 41 %, etc, so it has the reputation of "space metal". However, its low wear resistance limits the further development of titanium alloy. Besides, its high manufacturing cost, if only require the occasion of surface performance can reduce the use of the substrate, and then reduced the cost. Therefore, the study of aircraft titanium alloy is of great significance, the protection of titanium alloy includes alloying technology and coating technology. Alloying technology mainly adds other elements on its basis to improve the performance, while the most popular method is coating technology, the present, there are many coating technologies, include high-velocity oxy-fuel (HVOF), HVAF, cold spraying, laser cladding, laser micro-fusion in-situ synthesized technology, micro-arc oxidation, laser melt injection (LMI), supersonic laser deposition (SLD) and supersonic plasma spray technology, surface repair titanium alloy parts by cold spraying technology are good ways to solve those problems. Because of its low process temperature, no oxidation, only plastic deformation, and repair efficiency are high, the protective coating has high bonding strength and good impact toughness. In this paper, the types and applications of aircraft titanium alloys were reviewed, the latest research results of surface repair of titanium alloys parts by cold spraying technology were reviewed, technological parameters of the cold gas dynamic spraying technology was analyzed, including powder size of particles, morphologies, critical velocity, particle compression rate, substrate preheating effects on the particle/substrate adhesion, etc.