Removal behavior and output quality for laser chemical machining of tool steels

Laser chemical machining represents a promising technology for manufacturing metallic micro parts. It is usually based on the selective thermal activation of electrochemical material dissolution of self-passivating metals in an electrolyte environment. Prior to widespread industrial acceptance, its machining quality needs to be classified within the subtractive machining processes and the range of machinable materials needs to be expanded. For this purpose, line and square cavities with dimensions ≤300 μm are machined into high speed steel HS10-4-3-10 in a H3 PO4 -environment and compared to those of the self-passivating cobalt-chrome alloy Stellite 21. As a result, the laser-induced removal velocities in HS10-4-3-10 amount to 50 μm/s. These are two orders of magnitudes higher than the background etching (2 nm/s at room temperature) and three times higher than those obtained in Stellite 21 (12 μm/s). However, the microscopic and spectroscopic analyses of both materials reveal a high shape accuracy with edge radii from 10 to 20 μm, a surface roughness down to 0.8 μm and a negligible microstructural impact. Despite lower removal rates and higher surface roughness, laser chemical machining provides higher dimensional accuracy in comparison with micro milling and shows its suitability for micro machining of structures <200 μm.