Micro-laser assisted machining (µ-LAM) for ultra-hard and brittle optical materials

Materials like fused silica and borosilicate crown glass (N-BK7) have strong covalent Si-O bonds that make them hard but brittle due to the lack of dislocations for plastic deformation. Furthermore, materials such as tungsten carbide (WC) and silicon carbide (SiC) are extremely hard and brittle materials due to their strong covalent bonds (W-C in WC and Si-C in SiC), with SiC also exhibiting sp3-sp3 bond lengths that result in tightly packed atoms, further enhancing its resistance to deformation and breakage. Machining such materials is challenging; however, Micro-Laser Assisted Machining (μ-LAM) offers a promising solution. By applying laser energy to soften hard and brittle materials locally, μ-LAM facilitates the machining process, making it feasible to shape these hard materials. This study uses a Universal Mechanical Tester (UMT) to evaluate the cutting performance of brittle optical materials such as fused silica and tungsten carbide under various conditions, with and without laser assistance. By integrating a laser with a diamond cutting tool, improvements in material removal rates, surface quality, and overall cutting efficiency were evaluated. The experimental setup involves testing multiple rake angles to determine acceptable parameters for each material. The materials’ response to μ-LAM is meticulously analyzed through metrology and microscopic examination, focusing on surface integrity, ductile-brittle transition, and subsurface damage. The results demonstrated that μ-LAM significantly improves cutting performance by reducing cutting forces and enhancing surface finish. Optimized rake angles, nose radius, and laser parameters yield the best results, paving the way for more efficient and precise machining of hard and brittle optical materials.