Influence of multi-steps cut on stress evolution and surface integrity in machining of laser cladding layer

Abstract

In subsequent machining of heterogeneous cladding layers, it is often imperative to employ multi-steps machining to reach the required dimensional and geometrical accuracy. The present study primarily investigated the impact of cumulative effects of stress evolution on surface integrity in multi-steps machining of heterogeneous cladding workpieces by FEM and experimental methods. The FEM findings demonstrated that the stress induced by multi-steps machining was contingent upon the latter machining step, with lower interfacial stress difference when using a smaller thickness ratio for latter machining step compared to that by single-step machining. The experimental results indicated that the surface morphology was significantly affected by plowing when the total removal thickness ratio or the thickness ratio of latter cutting step is small. With larger total thickness ratio, otherwise, the surface morphology would be affected by larger interfacial stress difference. Also, great work-hardening was generated on the machined surface. Meanwhile, the cutting heat will promote gradient evolution of micro-hardness between cladding and substrate. In addition, the larger the thickness ratio in latter cutting step, the slightly lower of the tensile residual stress along the cutting speed direction is, while the residual stress in feed direction is mainly in a compressive residual stress state. Finally, the maximum surface integrity can be achieved by multi-steps machining with proper thickness ratio combinations. The study reveals the cumulative effects of stress arising from multi-steps and its effect on surface integrity, while offering theoretical guidance for the subsequent machining of heterogeneous cladding layers.