A new electric arc spraying method of using 321stainless steel wire as the anode and aluminum wire as the cathode can prepare a type of 321/Al composite coating. Similar with the arc spraying 321 stainless steel coating, the HVAS 321/Al coating has typical lamellar structure. Although the addition of aluminum in HVAS 321/Al process can not lead to metallurgical reactions between the anode and cathode feed stocks, a type of composite coating with “inter-deposited hard steel splats and ductile aluminum splats” is formed, and the residual stresses initiated from the spraying process are partly released or attenuated. In addition, the oxide content of the composite coating decreases to a low degree.
As compared with the HVAS 321 coating, the HVAS 321/Al coating has lower mean microhardness and different wear responses under the three different sliding conditions. The anti-wear property of HVAS 321/Al coating is lower in dry sliding but higher in the oil lubricated sliding with or without the oil-dipping pretreatment. Due to the porous structure of coatings, the oil-dipping pretreatment can be helpful to retaining the lubricant and supply it to the sliding surfaces, thus reduces the friction coefficient and enhances the wear resistant property. The well tribological behavior under the oil-lubricated conditions of the HVAS 321/Al composite coating is closely related to the typical “ductile/hard phases inter-deposited” structure of the coating. The decrease of oxide content (or thick oxide films) prevents the stainless steel debris from cracking or disintegrating, thus the delaminating wear process is controlled and prolonged. The well performances of the HVAS 321/Al composite coating provide the possibilities of applying this technology in special industry field with the requirements such as moderate hardness but high wear resistance and chemical stability.
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