The Research And Application Of Plasma Spray Remanufacturing Repair Technology Based On FV520B

Repair process is the most critical part of the remanufacturing. It includes repairing and upgrading the recovery parts to restore or exceed the quality standards of the new products. Thermal spray technology is an important part of remanufacture. Compared with other surface treatment technology, thermal spray technology achieves a synergistic effect in the true sense. In fact, it is one of the core technology of remanufacturing.The research object is FV520B which it is martensitic stainless steel used in compressor wheel. Taking into account the properties of the base material and repairing layer, We choose NiCrBSi-Mo powder as the main material for making the repair layer. Currently, it is widely applied on the remanufacturing of the surface to be repaired, So, NiCrB Si-Mo fully meets the requirements of FV520B used in the impeller remanufacturing.In this paper, basing on the principle of particle deposition of the thermal spray process, spraying process parameters were optimized, besides, the substrate pretreatment process of binding properties of the coating were studied.the research work was carried out as follows:(1). Analyze the formation mechanism of thermal spraying from the micro-levelAs particles reaching the molten bath area, the heating and melting process happens, and the molten particles will be driven to the surface by the high speed airflow based on the working principle of thermal spray. When the particles are moved to the substrate surface, the particles deposited on the surface mainly through the flat-type expansion and sputtering way. The droplet deposition process owes the deformation of particles and the hot exchange of the matrix with the particles. It can be found in the mathematical models that this process is closely related with the surface morphology of the substrate and substrate temperature, the velocity, quality, viscosity, etc. of the particle also have a close relationship.(2). Obtain the optimization parameters in the spraying process.Respectively, the paper use the orthogonal experiment and response surface design method to make the experiment, and obtain the test results in accordance with the experimental protocol. Range method is used to deal with the results of the hardness test, and then, the evolution of the coating hardness in different parameters is acquired, combined SEM image of the test. Rotation design analysis is respectively used to obtain the coating thickness and coating porosity response value. On this basis, the effects of multiple process parameters coupled laws to the coating thickness and porosity are considered.(3). Obtain the influence of coating pretreatment method for bond strength.Along with unit surface area of the substrate increasing, the bonding strength has been significantly improved. To achieve improved bonding strength of the coating machined grooves are prepared in the substrate surface for increasing the surface area of the base unit. The tests show that mechanical roughening or laser treatment is an effective method to increase the bonding strength between coating and substrate manner. Besides, the experiment shows that appropriate preheating temperature can improve the bonding strength of the coating and the substrate. In the process of spraying NiCrB Si-Mo powder on FV520B substrate, preheat temperature was maintained at 100 ℃, the droplet on the substrate surface can flat expanded matrix weak binding region between the coating and reduced bonding strength increases.