Microstructure and ProPerties of tiG surfacinG co-Based alloy on uMco50 Process Burner the surfacing layer of cobalt-based alloy is prepared using the tungsten inert gas welding (tig) process and employing the uMCo50, St1 and St6 filler materials. the metallographic testing, hardness, wear and corrosion testing of different surfacing layers have been carried out. each area of the surfacing layer is characterized using the optical and scanning electron microscope (SeM). Cellular and a few columnar dendrites have been observed near the fusion line of the uMCo50 surfacing layer, and cellular structure is observed in the central region. Dendrites and cellular crystals have been observed in the St1 and St6 surfacing layers. the average hardness of uMCo50, St1 and St6 surfacing layers are 320 HV, 672.3 HV and 497.5 HV, respectively. the wear loss of the St1, St6 and uMCo50 surfacing layer is 2.71 mg, 4.35 mg, and 14.57 mg, respectively. the corrosion weight loss of the St1, St6 and uMCo50 surfacing layers are 0.0388 g, 0.0477 g and 0.0833 g, respectively.
In order to solve the problem of the failure of the UMCo50 process burner, the orthogonal test was used to optimize the UMCo50 cobalt-based alloy TIG surfacing process, better joint performance was obtained for welding current of 120 A, surfacing speed of 12 cm min−1, interpass temperature of 50 °C and surfacing layer of 2 ∼ 3 layers; Tungsten inert gas(TIG) welding and plasma transferred arc weld(PTAW) surfacing were used to surfacing UMCo50 welding wire and T800 cobalt-based alloy powder on UMCo50 base metal. The structure, hardness, high temperature wear resistance and heat corrosion resistance of the surfacing layer were compared. The results show that UMCo50 surfacing layers are α-Co (fcc) and ε-Co (hcp); T800 alloy surfacing layers are mainly Co3Mo2Si, CoMoSi, α-Co and ε-Co. The Laves phase in the T800 alloy surfacing layer significantly improves its hardness and high temperature wear resistance; Under the same test conditions, the heat and corrosion resistance of the UMCo50 surfacing layer is significantly better than that of the T800 surfacing layer.
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