Study On The Microstructure And Properties Of 316L Stainless Steel Deposition Layer On The Turbine Blades Steel By High-energy Micro-arc Deposition Technology

Steam turbine blades, running for long time at the conditions of high temperature, high pressure, high speed, corrosion and water droplet erosion, can be easily damaged. The damaged blades will influence the safety and efficiency of steam turbine. Therefore, addition inoxidizing coating on blades of steam turbine and timely repair of blades have significant meaning to assurance safety and electricity production.The high-energy micro-arc deposition technology have advantages of convenient operation,small heat influence area, low cost, and not need heat treating after deposition. The microstructure and properties of 316L deposition layer on steam turbine blades 2Cr13 steel by HEMAD were researched. The main results are listed as follows:1. Orthogonal test was carried out based on the three main factors: power, frequency and voltage, which were all with three levels. Orthogonal analysis and variance analysis were applied in which microhardness, porosity, corrosion resistance and combination property were taken as the objects. Then the optimized parameters were obtained. When the argon flow rate is 8L/min, electrode moving rate is 1cm2/min, output power is 630W, frequency is 300Hz and voltage was 68V, the layer have the best properties.2. The microstructure and element composition of deposition layer and interface were researched by means of optical microscopy(OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) and energy dispersive system(EDS).The results show the substrate is composed of martensite. The deposition layer is composed of austenite and a little martensite. It was not found pores, cracks and other defects, with dense, uniform transition, also, EDS was used to study the diffusion of Cr,Fe,Ni,Mo elements along interface. It was found that the substrate and the deposition layer are well bonded. It is mainly metallurgical bonding.3.The microhardness of the deposition layer for optimized parameter layer is 1.4 times higher than that of the substrate. The microhardness of substrate near the layer is a little higher than that far from the interface. It is due to the work-hardening and the crystal thinning as well as the metallurgical bonding.4.The wear properties of deposition layer and substrate were tested. The morphology of wear surface and debris were analyzed. The results show that the wear resistance of deposition layer is higher than that of substrate. Substrate suffered mass loss for wear test, which contributed to abrasive wear pattern. However, it is different for 316L deposition layer. At initial stage of wear, the samples lose mass; with extended test time, the samples experienced subsequent mass loss and final mass gain, which indicated that the main wear pattern is adhere wear as mass loss, and oxidation and mass transfer as mass gain.5.The corrosion resistance of deposition layer and substrate were tested in FeCl₃+HCl+H₂O solution for 24 hours. The results show that the corrosion resistance of deposition layer is higher than that of substrate. The main corrosion pattern of substrate is crystal boundary corrosion, and that of deposition layer is pitting corrosion.