Effect of gas tungsten arc welding process variables on dilution and bead geometry of Stellite 6 hardfaced valve seat rings

Hardfacing is one of the surfacing methods most widely employed in valve manufacturing industries to deposit Stellite 6, a cobalt based alloy, on low carbon steel valve seat rings to enhance specific properties such as wear and corrosion resistance. Gas tungsten arc welding (GTAW) process is used for hardfacing smaller size valves. The quality of the hardfaced deposits depends on the degree of dilution. The control of dilution will result in better metallurgical and mechanical properties of hardfaced deposits. Mathematical models have been developed in this paper to study the effects of GTAW process parameters on dilution and other important hardfacing parameters, namely, penetration, reinforcement and bead width. Models have been tested for their adequacy by regression methods. The direct and interaction effects are presented in graphical form which can be used not only for the prediction of geometry but also for controlling weld bead quality.