Investigation Of Behavior And Life Evaluation Of Rolling Contact Fatigue Of Plasma Sprayed Coating For Remanufacturing

Remanufacturing is industrialization of maintain of waste electromechanical products using high and new technologies. At the same time, remanufacturing is also an effective approach for economizing energy, decreasing discharge and establishing amphitypy society. As rising mode of economy of homeland benign transformation, remanufacturing domain fleetly develops. More and more corporations engaging remanufacturing appear. More and more people are approval with the concept of remanufacturing. Many scientific problems about remanufacturing are dramatic. The problem of quality evaluation of remanufacturing product need be specially focused. Plasma spraying is a useful technology for remanufacturing. The life evaluation of remanufacturing product by using plasma spraying can be actually predigested to the life evaluation of surface plasma sprayed coating.Mechnism and method of rolling contact fatigue (RCF) life evaluation of plasma sprayed coating are investigated in the present paper. Fe-based coatings were depositted by plasma spraying technology. Optimization of spraying parameters was conducted by orthogonal design. Spraying distance, spraying volitage and spraying current were selected as orthogonal factors. The micro-hardness and porosity of the coating were used as evaluation criterions. Optimizational spraying parameters were obtained. The optimizational coatings own density microstructrue and high bond strength. A ball on disk RCF tester was introduced to conduct the RCF experiments of the coatings. Two-parameter Weibull distribution was used to evaluate the coating life.The influence of surface integrity on RCF behavior of coating was investigated. The influence of bond strength, surface hardness, coating thickness and surface roughness on RCF behavior of coating were investigated, respectively. Experimental results showed that deposition of undercoating not only increases the bond strength, but also improve the holistic RCF life. The reason is the increase of fatigue resistance of the coating/substrate interface. Nitridation of the coating surface increase the surface hardness, but decrese the holistic RCF life. After nitridation, the brittleness of coating was obviously improved, as a result, the crack sensitiveness increased. So the nitriding layers always sloughed in a short time. The increase of coating thickness by controlling the grinding process can improve the holistic RCF life. The relative distribution of shear stress within the coating is charged by increasing thickness, and the interface bears lesser stress. The decrease of surface roughness by using surface finishing machining can improve the holistic RCF life. The surfaec abrasion is alleviated for smooth coating.The influence of loading condition on RCF behavior of coating was investigated. The influence of contact stress and rotational speed on RCF behavior of coating were investigated, respectively. Experimental results showed that the increase of contact stress and rotational speed both obviously decrease the holistic RCF life. The intensive shear stresses within the coating or on the interface are the main drivers for coating delamination in a short time. The coating bears time after time altering shear stress in unit time when rotational speed is more rapid. The accumulate damage process charges quick. The nestification of stress may appear. As a result, the holistic RCF life reduces.Application of acoustic emission (AE) technology in on-line monitor of RCF process of coating was investigated. The comparison of sensibility of AE signal, acceleration signal and torque signal on coating fatigue fracture was conducted. The origin modes of AE signals within the coating were analyzed. The response of AE signal on accumulate damage process was addressed. The prewarning of coating failure based on AE signals was investigated. Experimental results showd that AE signal is more sensitive for coating fracture than acceleration signal and torque signal. At the same time, AE sensor can accurately capture the fatigue fracture within the coaitng. AE signal can also r feedback the accumulate damage process of the coating during RCF experiment. The prewarning mode based on AE signal can effectively predict the coming coating failure.Evaluation technology of bond strength of sprayed coating based on surface altering indentation was investigated. The mechnism and feasibility of surface altering indentation were discussed. The model machine of indentation device were designed and fabricated. The certification experiments were conducted. Experimental results showed that energe parameter of AE signal can be used as feature parameter to evaluate the bond strength of coating. The observations of the coating released that the surface altering indentation can effectively induce the interface crack, but no damages in the coating interior and substrate.