Optimization of machining parameters applied in hard turning of large components for cooling lubrication methods

Abstract

The increasing demands concerning renewable energy have required ever-bigger projects, as seen with wind turbine cases; in these large projects, the surface contact presents high load and wear resistance requirements. The cooling and lubrication methods in machining are highlighted due to the reduction of costs and environmental impacts. In functional hardened surfaces, it is critical to understand the integrity aspects once they significantly affect the durability of the component. This work clarifies, how the machining parameters of feed, depth of cut, velocity of cut, minimum quantity of lubrication, and abundant cooling affected the machined surface in a large component, with a discussion about microstructural altered layer, residual stresses, and Sa, Sq, and Sz statistical parameters. The results indicated that the minimum quantity lubrication and abundant cooling produced highly compressive circumferential residual stresses. Both methods produced surfaces free of significant microstructure altered layers. The altered surface layer was very thin when detected, with a thickness of up to 2.35 µm. On optimal conditions, the minimum quantity lubrication, in relation to abundant cooling, presented residual stresses 37% higher, a thickness of altered layer 74% lower, and Sa and Sz roughness, respectively, 47% and 11% lower and Sz 12% higher.