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Inconel 625 superalloy coatings were prepared on 12CrMoV steel plates by CMT process and MIG process respectively. The microstructures, the mechanical properties and oxidation resistance of the coatings were tested and analyzed. The results show that the heat input of CMT process is obviously lower than that of MIG process, and the forming quality of the coating is better, with smooth surface, no splash, no internal porosity and no other defects. The average weld penetration depth of CMT process coating is 0.51 mm and the dilution ratio is 6.8 %, which are much lower than that of the MIG process. Both coatings are mainly composed of coarse columnar crystals, however, the dendrites in the CMT process coating are finer and have better alignment consistency. The microstructure of two process coatings shows significant differences, and a large amount of Laves phase presents in the coating of the MIG process. The presence of Laves phase was not found in the coating of CMT process, but was replaced by element segregation region. In terms of mechanical properties, the CMT process coating has a higher hardness of about 221 HV and it is higher than the MIG process coating which is about 204 HV. Oxidation resistance testing of the coatings shows that the outer Cr2O3 film plays key role to the oxidation resistance. More compact and stable outer oxide film is formed in the oxidation process of the coating prepared by CMT process, which resulted in a better oxidation resistance.

Abstract CoMoCrSi superalloy coatings were prepared on Mar-M247 Ni-based superalloy by high velocity oxygen fuel (HVOF) under various spraying parameters. Dense coatings with porosity < 0.8% were prepared, and the fretting wear properties of the coatings was investigated. The coatings showed good adaptability to the spraying parameters. As the temperature increased from R.T. to 400 °C, the friction coefficient of the coating decreased from 0.8 to 0.6, and the wear morphology gradually changed from pits to bulges. A large amount of material transfer occurred, and the main wear mechanisms at R.T. were abrasive wear and delamination; adhesive wear appeared slowly at elevated temperatures. The coating exhibited better wear resistance than the substrate during the experiments. Highlights • How the spraying parameters effect the fretting wear behavior of high velocity oxygen fuel (HVOF) coating was concerned. • The effect of temperature on the friction and wear properties of coatings has been studied. The friction coefficient decreases with increasing temperature, but the materials loss had the similar rule • The wear mechanism was abrasive wear and delamination in RT, and adhesive wear appeared slowly at elevated temperature. [ABSTRACT FROM AUTHOR]