The Study Of Phosphating Application With Nano-Al₂O₃

Phosphating is a kind of common surface finishing technology, which is widely used in every industrial field for its good corrosion resistance, wearability, lubricating. Based on environmental protection, energy saving requirements, in recent years, researcher have done a lot of research work at room temperature, low-temperature phosphating, phosphating accelerator and others, and done well. However, some phosphate coatings need better wearing resistance performance. Many locomotive bearing parts need high strength wearability to bear hardware, such as gear, wheel, piston ring, valve and others needed phosphating treatment. But ordinary phosphating treatment connot meet the demands. So it is a new topic to work at environmental protection, low-power, wearable phosphating.It is researched broadly that using nanometer as composite coating. But I find few reports about nanometer application in phosphating in domestic and overseas.In our group, somebody had done research which 120 nm Al₂O₃ was added to phosphating solution to strength wearing resistance of phosphate coating. This paper is base on his research. In this paper, I try to do further interrelated research through putting 100nm Al₂O₃ into the phosphating solution. First of all, I have done the prophase experiment to determine basal formular, phosphating time, suited single dispersant and so on. Composite dispersant which has better distributed performance was singled out. Secondly, Al₂O₃ compound quantity in phosphate coating, hardness, SEM, wearing performance for adding different Al₂O₃ content were studied. Finally, formular was optimized by orthogonal test to select the best formular factor. At the same time, the reaction law of composite phosphate coating had a preliminary exploration.The medium temperature basal phosphating solution which has better corrosion resistance was determined through exploratory experiences during early days. Composite dispersant which was made up by HO(CH₂CH₂O)_nH and N(C₂H₅)₃ was chosen. Hardness reached maximum value HV167MPa, while friction coefficient was least, when nano-Al₂O₃ content was 10g/L in phosphating solution.The best factors which were determined by orthogonal test are nano-Al₂O₃ 6.0 g/L, vibration time 15min, phosphating time 12-15min, rate of total acid and free acid 10, pH 2.22. Phosphate coating formed under optimal fomular is light grey, uniform, fine and successive. Al₂O₃ exists on surface. Al element distributes uniform. Through the analysis with TEM, SEM, EMPA, I find that nano-Al₂O₃ is well dispersed, and well-proportioned distributing in phosphate coatings. Nano-Al₂O₃ composite phosphate coating crystallization is basically uniform. Through the tests with microhardness apparatus, roughness apparatus and multi-function apparatus, I find that when opportune quantity Al₂O₃ is added into phosphating solution, hardness, wear resistence, lubricating of phosphate coating is increased, and roughness and friction coefficient is decreased.