Experimental investigations on depth of penetration and surface integrity in AZ91/Al₂O₃ nano-composites cut by abrasive water jet

In the present study, an experimental investigation is conducted to determine the effect of process parameters on the depth of penetration and surface integrity in AZ91-metal matrix composite containing 1, 1.5, and 2 wt% of Al₂O₃ nano-particles through abrasive water jet cutting. Mixed level L18 orthogonal array is employed to conduct linear cutting experiments for both base alloy and nano-composites. Stir casting method is used to produce metal matrix nano-composites. The micro-mechanisms involved in material removal process are analyzed using SEM. Surface integrity of cut surfaces has been characterized using surface topography and 2D roughness profile observations. Water pressure and traverse speed are found to be the most significant factors in deciding depth of penetration. Penetration ability of nano-composites is decreased with increase in wt% of nano-Al₂O₃ particles. Two cutting regime, i.e., cutting wear and deformation wear, are observed from the SEM analysis and these mechanisms are found similar to the material removal mechanism in Mg alloys and other ductile materials. Contribution of high speed water jet to material removal process is also discussed. Embedment of sharp edged and spherical abrasive particles is observed in the micro-cutting and deformation regions. Surface quality produced by abrasive water jet in nano-composites found increased with increase in wt% of Al₂O₃ when compared to base alloy. Traverse speed, water pressure, and garnet size showed significant effect on surface quality produced by abrasive water jet. Micro-melting was observed in a few regions of the cut surfaces in nano-composites and melted region is affected by oxidation. Formation of short continuous ribbon type chips was also observed in some regions of cut surfaces, indicating the shear mechanism is also involved in the cutting process.