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Inconel 625 surfacing specimens were prepared on the surface of carbon steel by GMAW welding. The microstructure was studied by OM, SEM, XRD and TEM, and the tensile properties were analyzed at different temperatures. The results show that the main precipitates are Laves phase and MC carbides. The tensile properties are strongly dependent on temperature, and there is an obvious intermediate temperature brittleness behavior. With the increase of temperature, the tensile strength (below 700 °C) and yield strength (below 760 °C) decrease slightly, however decrease significantly after the temperature exceeds 700 °C. However, the tensile plasticity decreased significantly, and reached the lowest value at 700 °C. The TEM observation shows that the main deformation mechanism of dislocation is cutting precipitates at 20 °C–700 °C. Some continuous stacking faults and K–W locks can be observed at 700 °C. At 760 °C, the dislocation loops appear in the microstructure, that is, the dislocation bypass mechanism starts. At 800 °C - 900 °C, the dislocation networks were observed in the microstructure, and the bypass mechanism was dominant.