| As an emerging industry,remanufacturing is a key step in the implementation of sustainable development strategy in China.As a part in the remanufacturing process,remanufacturing repair determines the quality of the final remanufactured product.The remanufacturing repair technology can repair the damaged parts of the parts by using the special properties of the repair coating,so that the quality of the remanufactured products can reach or even exceed the new products.Large fan has high cost,high added value and high remanufacturing value.The failure behavior of fan impeller is mostly caused by erosion and wear of solid particles.Cr3C2-NiCr coating has excellent wear resistance and corrosion resistance,and its application in fan impeller,axle and other parts can effectively improve the service performance of the fan.As a kind of inherent structure of coating,porosity is the key factor affecting the quality of coating.The preparation process of Cr3C2-NiCr coating was studied by taking the coating pores as the research point,aiming at the abrasion resistance of the coating in the oil immersion environment and the erosion resistance of the coating in the neutral salt spray corrosion environment.Firstly,the effect of spraying process on pore morphology of coating was studied.Spraying power,powder feed rate and spraying distance are the three main factors that affect the pore morphology of the coating.Within a certain range,when the spraying power increases from 25kW to 45kW,the coating porosity will decrease from 17.67%to 3.07%.When the powder feed rate gradually increased from 18g/min to 45g/min,the porosity of the coating first decreased and then increased,and the porosity decreased from 5.69%to 2.45%and then increased to 5.20%.When the spraying distance increased from 80mm to 100mm.the porosity increased from 4.08%to 5.57%.Due to the different depositional environment,the phenomenon of "pore aggregation" will occur in the coating,and the pores are mostly concentrated in the position of the coating near the bonding interface.The higher the overall porosity of the coating,the greater the proportion of pores with large equivalent diameter.The pore shape is random,and most of them are equiaxed or nearly equiaxed.Secondly,the effect of pores on the microhardness distribution of the coating was studied.The coating was divided into near-surface area,central area and near-binding interface area,and the pore distribution in different areas was statistically analyzed.It was found that the distribution of microhardness inside the coating was related to the pore distribution.The phenomenon of "pore aggregation" is inevitable,but the pore structure can be effectively reduced by adjusting the spraying process,so as to increase the microhardness of Cr3C2-NiCr functional layer.Then,the effects of the interactions of power,powder feed rate and distance on the porosity and microhardness were studied.The central composite test was designed by response surface method to optimize the porosity and microhardness of the coating.The results show that the interaction between powder feed rate and spraying distance has a significant effect on the porosity and microhardness of the coating,while the interaction between spraying power and other influencing factors is not significant.Within the selected process range,the minimum porosity of Cr3C2-NiCr coating was estimated to be 2.216%,corresponding spraying power P=37.63kW,powder feed rate F=32.14g/min,and spraying distance D=84.71mm.The maximum microhardness of Cr3C2-NiCr coating was estimated to be 1030.8HV.At this time,spraying power P=39.16kW,powder feed rate F=31.94g/min,spraying distance D=93.54mm.The response curve obtained by the regression model shows that there is a negative correlation between coating porosity and microhardness,that is,the higher the coating porosity is,the smaller the microhardness is.Finally,the abrasion resistance of coatings with different porosity under oil immersion and erosion resistance under salt spray corrosion environment were evaluated,and the influence mechanism of different pore structure on the oil immersion friction behavior and erosion resistance after corrosion was analyzed.In the oil immersion friction environment,for the same coating,increasing the load can reduce the coating friction coefficient,and in the same load,impro’ving the porosity can reduce the coating friction coefficient,but the higher the porosity,the higher the wear weight.The wear mechanism of the coating with different porosity is different in the oil immersion environment.The high porosity coating is mainly abrasive wear,while the low porosity coating is mainly adhesive wear.In the salt spray corrosion environment,the higher the porosity of Cr3C2-NiCr coating,the worse the corrosion resistance.Salt spray corrosion changed the erosion mechanism of Cr3C2-NiCr coatings,the erosion resistance of the coating after corrosion decreased seriously,and the higher the porosity,the worse the erosion resistance of the coating.Improving the salt spray corrosion resistance of Cr3C2-NiCr coating can effectively improve the erosion resistance of the coating in the Marine environment. |
