Experimental study and optimization of cutting parameters in machining of super alloy with hybrid ultrasonic method

Super alloys are intensively used in various industries, especially in the aerospace industry, because of their special characteristics. A number of holes are sometimes required to be drilled into super alloys for aircraft at their final stage assembly. In the present study, a hybrid ultrasonic machining method, called rotary ultrasonic machining (RUM), was successfully used in super alloy drilling. The empirical modeling of the process parameters of RUM was performed for the super alloy (Inconel 718) using an experimental design approach, called response surface methodology (RSM). Parameters, namely tool rotation, feed rate, ultrasonic power, and abrasive grit size, were selected as input variables. The others were kept constant. The performance was measured in terms of the machining rate and the surface roughness. The developed models were found to be reliable representatives of the experimental results with prediction errors less than ±5%. Moreover, the feed rate for the quality and productivity aspect was found to be the most critical factor. The optimized values of the machining rate and the surface roughness achieved through a multi-response optimization were 0.9 825 mm³/s and 0.951 μm, respectively.