Predicting the coolant lubricating properties based on its density and wetting effect

Introduction. The processes occurring in the cutting zone contribute to the rapid wear of the cutting tool and a decrease in the quality of the workpiece. It is possible to reduce the impact of negative factors during metal cutting through a rational choice of coolant. The aim of the work is to develop a methodology for the accelerated assessment of the coolant lubricating properties. Methods. Experimental studies of the lubricating effect of seven different grades of coolant, during friction of a T15K6 (15% TiC–79% WC–6% Co) hard alloy pad and a rotating roller made of carbon structural Steel 45 (0.45% C) are presented. As a parameter of coolant efficiency in terms of lubricating effect, paper proposes an efficiency coefficient Kc, which is equal to the ratio between the friction coefficient that occurs when using coolant and the friction coefficient during friction without coolant. The lower the coefficient Kc, the more effective this coolant is in terms of lubricating effect. Results. Empirical dependences of the coefficient Kc on the coolant density ρ and the limiting wetting angle Θ (Kc = f(ρ;Θ)) are established. Since the low significance of the parameter ρ is established, the formula for the dependence of the Kc only on the limiting wetting angle Θ (Kc = f(Θ)) is established in the work. It is established that the dependence formula (Kc = f(Θ) provides the highest accuracy of calculations. Discussion. After evaluating the research results presented in this paper, the following conclusions are made: 1) the paper establishes the influence of the coolant density and the limiting wetting angle on the coolant efficiency coefficient for the lubricating effect determined for the friction between a roller made of Steel 45 and a pad made of T15K6 alloy: Kc = f(ρ;Θ) and Kc = f(Θ); 2) the greatest accuracy of calculations from 2.75 to 15% is provided by the formula for the dependence Kc = f(Θ); 3) the dependence Kc = f(Θ)is proposed to be used for the method for the accelerated assessment of the coolant lubricating properties during friction of a pad made of T15K6 alloy and a rotating roller made of Steel 45. The proposed method consists in measuring the limiting wetting angle of a coolant drop on the surface of the workpiece and calculating the derived empirical dependence of the coolant efficiency coefficient on the lubricating effect.