Multi-response parametric optimisation of abrasive waterjet milling of Hastelloy C-276

Abrasive waterjet (AWJ) milling is a rapidly evolving research topic in the development of unconventional methods for machining high-strength materials without affecting their physical and thermal properties. It is considered as a promising technique for machining milling pockets in Hastelloy C-276. In the present study, the AWJ milling behaviour of Hastelloy C-276 was examined with the purpose of evaluating the performance parameters, namely the material removal rate and surface roughness (R-a). The considered input process parameters included the waterjet pressure, step over, traverse rate, and abrasive flow rate. The response surface methodology with a Box-Behn ken design was used to perform the experiments, which involved 29 machining runs. Analysis of variance was used to identify the significant parameters of the machining process, and the optimal process parameter combination for achieving a high material removal rate and low surface roughness was established with the aid of response surface graphs. Multi-response optimisation based on grey relational analysis was also performed taking into consideration the overall output response. The waterjet pressure and traverse rate were identified as the primary determinants of the material removal rate, whereas the step over was the predominant factor of the surface roughness. The selected AWJ milling conditions based on grey relational analysis approach were examined using surface morphology, surface topography of milled pockets on Hastelloy C-276.