Study On Heat Resistant Anti-wear Nano-composite Coating

Wear is one of the forms of material failure. In order to reduce the abrasion, the wear-resistant coating has been developed rapidly. Usually some reinforcing fillers are added in the coating to improve the wear resistance, which have high hardness, high strength, self-lubricating and wear-resistance, such as aluminum oxide, silicon nitride, silicon carbide, graphite, mica, carbon fiber, glass fiber, and whisker, etc.In recent years, the multi-functional coatings with wear-resistance and high temperature performance simultaneously have been required. So a variety of heat resistant anti-wear coatings using different high temperature performance polymers as the coating film-forming material were developed. Generally the heat resistant high-performance polymers exhibit poor processing behavior, which greatly limits their applications in many fields. Poly(phthalazinone ether)s, developed by our research group, have balance of high temperature performance and good processing properties owing to their unique twisted and non-coplanar phthalazinone structure. They can be soluble in some organic solvent at room temperature. Therefore it has been used in many high temperature fields.In this paper, one of the poly(phthalazinone ether)s, poly(phthalazinone ether nitrile ketone)(PPENK), was used as the film forming material of the composite coating to play a role in improving the heat-resistance. The inorganic nano-particles SiC and Si3N4which have the high hardness and strength, were chose as the reinforcing filler. Then a series of heat resistant anti-wear composite coatings were prepared by ultrasonic blending method.To improve the dispersion of nano-particles in the coating, the ultrasonic processing technology, coupling agent and its dosage was investigated by observing the filler’s settlement time. The best ultrasonic processing technology was frequency25%, amplitude03-03, tim e30s. For the nano-SiC, the coupling agent KH550of0.5wt%, and for the nano-Si3N4, the coupling agent A-171of3%. The excellent dispersion effect could be obtained.The properties of the composite coating were investigated including the basic properties (adhesion, impact strength, flexibility and hardness) and the tribological properties (friction coefficient and wear mass loss). Scanning electron microscopy (SEM) was used to observe the worn surface of the coatings. The results indicated that when the resin PPENK content is18%and the filler content is5%in the PPENK/Si3N4composite coating system, the coating show the best tribological properties. Its wear mechanism was mainly plough wear; when the resin PPENK content is22%and the filler content is5%in the PPENK/SiC composite coating,, the coating showed the best tribological properties. Its wear mechanism was mainly adhesive wear; when the resin PPENK content is22%, and SiC/Si3N4is3/2in the PPENK/SiC/Si3N4composite coating, the coating showed the minimum friction coefficient, and when the resin content is20%, and SiC/Si3N4is1/1, the coating showed the lowest wear mass loss, its wear mechanism was mainly adhesive wear and some plough wear.