INVESTIGATION OF SURFACE CHARACTERISTICS IN PRECISION HOLE MACHINING OF INCONEL-625 USING ABRASIVE AQUA JET DRILLING

Abstract

Inconel-625 is a high-performance nickel-based superalloy which offers exceptional properties such as extensive resistance to corrosion, high strength-to-weight ratio, hardness, and impressive heat tolerance. Machining precise holes with required dimensional accuracy is challenging in Inconel-625 using conventional drilling processes. The investigation aims to improve the quality characteristics of hole machined on Inconel-625 by using the abrasive aqua jet drilling (AAJD) process. The influence of jet pressure ($J_P$), table feed ($T_F$), mass flow rate ($M_{\mathrm{\text{FR}}}$) and gap distance ($G_D$) on the erosion rate ($E_R$), surface roughness ($R_a$), circularity error (CI${}_{\mathrm{\text{error}}}$) and striation zone ($S_{\mathrm{\text{ZN}}}$) are investigated. The weighted principal component analysis (WPCA)-based response surface methodology (WPC-RSM) is employed to analyze and optimize process parameters. The optimal parameter settings ($J_P$ -300 MPa, $G_D$-1.5 mm, $T_F$-64 mm/min, $M_{\mathrm{\text{FR}}}$-0.55 kg/min) are observed to produce substantial improvement in response. Comparing initial and optimal conditions, the surface roughness ($R_a$) is decreased by 10.15% from 3.25 $\mu$m to 2.92 $\mu$m. The CI${}_{\mathrm{\text{error}}}$ and $S_{\mathrm{\text{ZN}}}$ are also reduced by 38.02% and 12.74%, respectively. The erosion rate ($E_R$) is improved by 8.79% with the optimal settings. $J_P$ is found to be the most influential parameter, followed by $M_{\mathrm{\text{FR}}}$. Scanning electron microscopy (SEM) pictures and 3D roughness plots are used in the surface topography analysis.