Research Of Micro-Arc Spark Deposition And Cladding Strengthening Technology On SCH13 Steel

In modern industry, the heat-resisting steels are wildly used in the components under high service temperature due to its excellent oxidation resistance and heat resistance. As a kind of heat-resisting steels, SCH13 steel is widely used in the production of electric furnace, annealing rolling production line and high-temperature furnace rollers. However, because of its poor wear resistance, the service life of components is adversely affected. The development of micro-arc spark deposition (ASD) provides an effective means of surface hardening for the heat-resisting steel.In this paper, Micro-arc spark deposition with Stellite 6 alloy as the coating material on SCH13 steel substrates was carried out using high-energy micro-arc process. The microstructure, chemical compositions, phase identification and hardness of the deposition layers were examined by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and microhardness tester, respectively. Meanwhile the form and growth mechanism of deposit were focused on. Moreover, through high temperature oxidation, the property for samples of resistance to high temperature oxidation was analyzed systematically.The results show that the morphology of the single pulse deposit is splashshape. A large number of the single pulse deposits were superimposed continuously and then deposition layers with a certain thickness were formed. The epitaxial growth coating with columnar grains was then achieved by micro-arc spark deposition. The coating of Stellite 6 alloy has a good metallurgical combination with the SCH3 steel substrate and the dilution rate of the coating is very low. The coatings were consisted ofγ-Co solid solution and chromium carbides. Because of the effects of the temperature gradient and the solidification rate, the microstructure of the deposition layer is slightly coarser with the increasing of the processing voltage. The average hardness of the coating is significantly increased compared to that of the Stellite alloy electrode and SCH13 steel substrate. The average hardness of Stellite 6 alloy coating is about 600⁷00HV, which is about 200HV higher than that of Stellite 21 alloy coating and 3 times higher than that of SCH13 steel substrate, and the average hardness of the two deposition layer is slightly decreased with the increasing of the processing voltage. After 80 hours of high temperature oxidation in 900℃, we can see the Stellite alloy oxide layers mainly contained chromium oxides, and the surface oxide film of SCH13 steel was mainly consisted of Fe₂O₃ and NiCr₂O₄, the weight of the SCH13 steel sample, Stellite 6 sample and Stellite 21 sample is increased 1.375mg/cm², 0.548mg/cm² and 0.785mg/cm², respectively. The property for Stellite samples of resistance to high temperature oxidation is obviously better than SCH13 steel substrate, and among them, the property of Stellite 6 sample is the best.