Plasma Spray Surfacing Technology

In this paper, according to the current valve domestic situation of plasma welding method, and valve structure, usage requirements, in China and abroad, use Co-based stellite 6 powders on Q235 steel plate as the base material test and further optimize the welding parameters. Use the same content material and the same process parameters compared the weldability and economy with manual plasma welding. Optimize the welding process parameters on this basis, and in practical welding test on the valve parts. Study in such factors as cost efficiency and welding process parameters on plasma surfacing layer and properties in different welding method.Plasma welding process parameters act an important part on the performance of surfacing layer significantly. Research the welding process on the hardness of weld overlay by testing the surfacing layer hardness. Testing found that when welding current is 160A, powder feeding rate 6.0g/min, powder feeding gas flow 3.5L/min, plasma gas flow 3.5L/min, welding speed 500mm/min, the surfacing layer of minimum dilution rate, was 3.78%, and the surfacing layer has the highest surface hardness values at the 666HV. In the other process parameters under certain conditions, the welding current on weld overlay performance was the most important. With the current increasing the dilution rate of surfacing layer increased gradually, and thus lead to decreased surface hardness of the layer. The hardness reduces from the top to base metal.Cobalt alloy plasma surfacing layer was formed by Fusion zone (binding) sub-layer, cellular crystal layer near the fusion zone, and a certain direction in front of sub-layer crystal asperata. A high hardness of the alloy solid solution formed after surfacing welding, making the surface hardness and wear resistance of surfacing layer are significantly enhanced. When the welding current is greater than 195A, microstructure significantly worse, prone to crack, due to heat input capacity, need to take precautions when welding.This study found that under the same parameters, plasma powder welding layer surface hardness was greater than the hardness of plasma manual welding by 8.1%, dilution rate lower by 6%, with excellent weld surfacing and stable welding quality, welding in lower current condition, and can be a shape at one time. Compared with manual plasma welding, the powder plasma welding has a better performance in material utilization, productivity, processing efficiency.