Plasma spraying technology is one of the thermal spraying technologies in surface engineering.Due to the characteristics of high temperature, energy concentration and controllable spraying atmosphere, plasma flame flow is a good heat source for all kinds of refractory materials, and the powder material has a high flying speed in the flame flow, so it provides conditions for obtaining a coating with good combination and compact structure.
一. technological features of plasma spraying
(1) the matrix is less heated, the parts are not deformed, and the heat treatment state is not changed.
(2) a wide range of materials can be sprayed, coating types.
(3) stable process, high coating quality.
二. Application of plasma spraying technology
With the development of aero-engine to high performance, high refurbishment life, high reliability, low fuel consumption and low cost, thermal spraying technology has been developed rapidly.More than 3,000 surfaces of a new engine with thousands of parts need to be coated with thermal spraying technology, which shows that thermal spraying technology has been widely used in the aviation industry.Among them, due to the advantages of low cost, high efficiency, simple operation, good coating quality and suitable for large-scale mass production, plasma spraying has accounted for more than 80% of all spraying parts of aeroengines.
The thermal spray coating of aero engine mainly includes wear-resisting coating, thermal barrier coating, sealing coating and high temperature protection coating.
1.Wear resistant coating
Because the working condition of aero engine parts is very bad (high temperature, high speed, vibration and high load), and suffer several types of wear such as adhesion, abrasive, corrosion and fatigue, the performance and service life of the engine are affected.
2.Seal coating
Aviation gas turbine engines have relatively complete air sealing system.The system consists of 40 ~ 60 sealing devices between the shaft, drum, rotating blade tip, compressor and turbine. The quality of the sealing device directly affects the power, thrust and efficiency of the engine.For example, for the sealing of turbine outer ring (i.e. blade tip radial clearance), according to the design requirements, turbine efficiency loss increases by 1% to 3% for every 1% increase in the ratio of blade tip clearance to blade length.It can be seen that gas road sealing is one of the important ways to improve efficiency and performance.For this reason, the wear-able sealing coating is often used in the design to achieve the purpose of sealing air road.
Thermal spraying seal coatings are divided into two categories, namely active grinding coating and abrasive coating (passive).
(1) active grinding coating (abrasive) is generally a hard anti-wear gray alumina coating, sprayed on the sealed grate.As the rotor rotates at high speed, grind its corresponding metal honeycomb sealing mass like a grinding wheel, and try to keep itself from being worn.This requires that the coating binding strength is high, hardness is high, heat insulation performance is good.
(2) can wear coating for coating, soft and easy to grind and embellish nutrient-laden "performance, shock resistance, resistance to reting performance, and combined with the matrix has a good performance, with the further development of plasma spraying technology and relevant supporting system, plasma spraying technology in aircraft engine coating products will get more extensive application.