Hao Xu

Molybdenum (Mo), owing to its excellent high-temperature resistance and low sputtering yield, is widely used in advanced equipment such as extreme ultraviolet (EUV) lithography systems. To meet the demand for regulating the surface wettability of Mo, this study employs micromilling to fabricate microgroove arrays on Mo surfaces to enhance their hydrophobicity. First, comparative micromilling experiments are conducted under flood cooling and minimum quantity cooling lubrication (MQCL) conditions. The effects of process parameters, including axial depth of cut (a_p), spindle speed (n), and feed per tooth (f_z), on burr height (H) are investigated under the two cooling/lubrication conditions. The results show that the burr heights obtained under flood cooling are generally lower than those obtained under MQCL. Subsequently, the machining parameters under flood cooling are evaluated using an orthogonal experimental design. A mathematical model relating the microgroove array geometry to the contact angle is then established based on Gibbs free energy to guide the design of surface microgroove structures. Finally, microgroove arrays are fabricated on Mo surfaces using the preferred machining parameters. The results demonstrate that the microgroove arrays effectively enhance the water hydrophobicity of the Mo surface. The static water contact angle increases from 62.45 ± 0.25° for the untreated Mo surface to a maximum of 128.50 ± 0.12°, thereby achieving a transition from hydrophilic to hydrophobic behavior.

Molybdenum (Mo), owing to its excellent properties, is widely used as a plasma-facing material and is recognized as a typical difficult-to-machine material. Achieving high-quality, low-damage machining is essential for ensuring the service reliability of Mo components. However, studies on the milling of Mo remain limited. Therefore, this study investigates a high-quality, low-damage milling technique for Mo based on analyses of milling force, machined surface roughness, and white layer formation. First, the effects of machining parameters, including radial depth of cut (a_e), spindle speed (n), and feed per tooth (f_z), on the responses, namely milling force (F) and surface roughness (R_a), were investigated. The relationships between milling force, surface roughness, and white layer formation were analyzed. Subsequently, the response surface methodology (RSM) was employed to reveal the influence mechanisms of the machining parameters and their interactions on the response variables. Finally, a Kriging surrogate model integrated with the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was adopted to identify the optimal machining parameter combination for high-quality, low-damage milling. The results indicate that the milling force and white-layer thickness exhibit consistent increasing trends with increasing feed per tooth under the investigated conditions, demonstrating that controlling the milling force is an effective approach for achieving high-quality, low-damage milling of Mo. For the simultaneous minimization of milling force and surface roughness, the optimal machining parameters were determined to be a radial depth of cut of 0.2101 mm, a spindle speed of 10,090.7 rpm, and a feed per tooth of 0.01 mm/z. These findings provide valuable process parameter guidance for the precision machining of Mo components.