Fabrication of coated tool with femtosecond laser pretreatment and its cutting performance in dry machining SLM-produced stainless steel

Abstract

Selective Laser Melting (SLM) technique applied to the stainless steel has been developing rapidly in the biomedical and aerospace industries. However, a post-machining is still needed to efficiently improve the surface finish and dimensional precision of the SLM-produced stainless steel parts. Dry machining (machining without the using of cutting fluid) is attracting interest around the world, which can reach green manufacturing without water pollution, residue on the swarf, and danger to health. In this work, to achieve the green finishing machining of SLM-produced AISI 316 L stainless steel, the hard coated tools with a nanotextured substrate were designed, and the key preparation methods of this developed tools were presented. First, a periodic nano-ripple structure (nanotexture) was induced by femtosecond laser scanning on the WC/Co substrate tool with different processing parameters, then TiAlN film was deposited on the nanotextured substrate surface using the cathode arc-evaporation technique without employing any interlayer. The surface micro-topography and mechanical property of the nanotextured TiAlN coated surface were studied. Machining tests without cutting fluid were performed on the SLM-produced stainless steel using the developed tool, and the cutting tool without laser pretreatment was also employed for the comparison. The obtained results demonstrate that, the TiAlN coatings adhesiveness is significantly enhanced by the femtosecond laser-induced periodic structure on the WC/Co substrate, and the critical load of the TiAlN coatings is increased from 57 to 73 N. The improved machining performances of nanotextured tools in drying cutting SLM 316 L stainless steel are achieved, resulting in a decrease of 10–20% in cutting forces, a decrease of 10–15% in cutting temperature and a high surface quality of the machined workpieces at the high cutting speed. The possible mechanisms for the effects of femtosecond laser pretreatment are discussed.