Mechanism and enhanced grindability of cryogenic air combined with biolubricant grinding titanium alloy

Grinding is an essential method for ensuring the machining accuracy and surface quality of difficult materials, such as aerospace titanium alloys. However, the deterioration of workpiece surface integrity due to thermal damage is the technical bottleneck of titanium alloy grinding. Therefore, a new enabling grinding technology for cryogenic air combined with a biolubricant is proposed. The introduction of cryogenic air leads to fundamental changes in the physical properties and lubrication mechanism in the grinding zone. On this basis, the formulas between the cryogenic air temperature and biolubricant temperature, kinematic viscosity, and surface tension coefficient are established. Under the same grinding parameters, compared with dry grinding, the normal force, tangential force, specific grinding energy, friction coefficient, temperature, and surface roughness value of cryogenic air minimum quantity lubrication decrease by 47.6%, 44.3%, 45.1%, 19.8%, 43.9%, and 46.3%, respectively. Then, the influence law of single and multiple factors on the grinding effect is discussed. When the peripheral speed, feed speed, and grinding depth are 30 m/s, 6 mm/s, and 30 µm, the optimal combination of factor parameters is a cryogenic air temperature of − 50 °C, an air pressure of 0.4 MPa, and nozzle inclination angle of 16°. Furthermore, on the basis of the multifactor orthogonal experiment, the quantitative mapping relationship between different grinding and influence factors is investigated to achieve optimal workpiece surface quality. This research provides a new effective method for improving the high surface integrity of grinding titanium alloys by using the cryogenic air minimum quantity lubrication method.