Novel beam scanning optimisation in laser cladding by solving the inverse problem of heat placement

Additive manufacturing by laser cladding has gained popularity in recent years but optimising the outcomes (e.g. microstructure) remains a challenge due to the difficulty of heat placement control. To address this, research has been conducted to generate a more uniform temperature distribution to seek hinger mechanical properties by beam oscillation strategies. However, these approaches need to determine the optimal conditions from a significant number of parameter combinations, which requires extensive iterative trials. Moreover, fixed parameters and constant motion paths still generate localised laser energy concentrations. In this work we proposed a novel laser beam scanning optimisation approach, whereby the heat placement can be controlled by tuning the laser beam configuration through solving the inverse problem. Unlike conventional approaches, it directly derives optimised parameter patterns from a target temperature distribution, eliminating the need for iterative simulations and experiments. A speed-controlled beam path strategy is implemented to realise a uniform target temperature on the wire feeding surface during stainless steel 316L deposition. Thermal analysis proved that the optimised system achieved the uniform temperature distribution on the cladding surface, within the target temperature on the cladding surface for ensuring a thermally and microstructurally stable deposition. Experimental characteristics also confirmed that suppressing temperature fluctuations and the effectively restriction of grain coarsening and precipitation, leading to a substantially finer and more homogeneous grain structure compared to the conventional linear scan. This research also shows potential for future application of other laser heat placement control processes such as selective laser melting or laser heat treatments.