An Experimental Investigation on Machining of Hardened AISI 440C Stainless Steel Using Abrasive Water Jet Machining Process

The present study attempts to analyze the impact of abrasive water jet machining (AWJM) process parameters on surface roughness and kerf taper properties of hardened AISI 440C stainless steel. Considering process parameters such as jet-water pressure, nozzle traverse rate, and stand-off height, the experiments are planned using the central composite design (CCD) of response surface methodology (RSM). Analysis of variance (ANOVA) is applied to the experimental data to determine which process parameters significantly affecting the surface roughness (R-a) and kerf taper properties. It is observed that surface roughness and kerf taper are significantly affected by all the three mentioned process parameters. Surface roughness decreases by increasing jet-water pressure. R-a decreases with a decrease in stand-off height and nozzle traverse rate. Kerf taper decreases by increasing jet-water pressure. After that, it decreases as the nozzle traverse rate and stand-off height decrease. Both coded and uncoded responses are incorporated into the developed predictive model. The study finds that the model's predicted values agree with the observed data. The next step involves optimization, i.e., adjusting the process's variables until the surface roughness and kerf taper are minimized. Furthermore, the machined surface of the work material was carefully analyzed under the optical microscope to give preliminary insight into the surface profile and waviness. The erosion made by abrasive particles is visible. To gain further insight into the machined surface characteristics, it was further observed using microscopic at 100x magnification. The machined samples were then scanned using scanning electron microscopy (SEM) for microstructural study and analysis.