Sensitivity analysis of process parameters in PTA hardfacing of valve seats using response surface methodology

The quality of a weld joint is strongly influenced by process parameters used during the welding. In order to have high quality welds, mathematical models that can predict the weld bead geometry and shape relationships have to be developed to accomplish the desired mechanical properties of the welding. This paper focuses on the development of mathematical models using response surface methodology (RSM) for the selection of process parameters and the prediction of bead geometry (penetration, reinforcement, dilution, bead width and total area) in automatic PTA (plasma transferred arc) hardfacing. RSM facilitates the optimisation of process parameters. Five factors were incorporated into the regression model: arc current, welding speed, powder feed rate, oscillation frequency and torch standoff. A sensitivity analysis has been conducted to compare the relative impact of five process parameters on bead geometry in order to verify the measurement errors on the values of the uncertainty in estimated parameters. The results obtained show that developed mathematical models can be applied to estimate the effectiveness of the process parameters for a given bead geometry, and a change of process parameters affects the penetration, dilution and bead width more strongly than reinforcement.