Formulation Design and Comprehensive Performance Evaluation of a New Sulfur-containing Water-based Semi-synthetic Cutting Fluid for GH4169 Processing

To address the problems of high cutting forces, high cutting temperatures, and severe tool wear encountered during the machining of the nickel-based high-temperature alloy GH4169, a novel sulfur-containing water-based semi- synthetic cutting fluid was formulated and evaluated. Using 2, 3-bis(Z)-12-hydroxyoctadec-9-enoyloxypropyl (Z)-12- hydroxyoctadec-9-enoate (E-S545) and butyl (E)-18-sulfooxyoctadec-9-enoate (BSO) as the core lubricating and extreme- pressure components, the formulation was blended with polysorbate 80, polyethylene glycol mono-4-nonylphenyl ether, 2, 8, 9-Trioxa-5-aza- 1-borabicyclo3.3.3 undecane, benzod isothiazol-3-one, and 2-methyl-4-isothiazolin-3-one. The cutting fluid concentrate was prepared using a process route of “aqueous phase first, then oil phase; functional components first, then auxiliary additives.” Test results on physicochemical properties indicate that the 5% diluted solution of this cutting fluid has an initial pH of 9.9 and maintains good alkalinity reserve and emulsion stability even after 28 d of standing and mixing with GH4169 nickel chips. Test results for wetting and spreading properties show that the surface tension is 25.41 mN/m and the contact angle is (8.9±1.2)° (n=5), demonstrating strong interfacial spreading and penetration capabilities. The four-ball test results show that the PB value of the in-house-developed cutting fluid reaches 133 kg, and the PD value reaches 513 kg, demonstrating superior extreme-pressure load-carrying capacity and anti-wear performance compare to the two commercially available cutting fluids. A 12-hour continuous cycle stability test show that the pH value of the self-developed cutting fluid maintain at 9.1-10.3, the surface tension is 25.41 mN/m-31.95 mN/m, the PB value maintains above 121 kg, and the total number of colonies is 1.5×10⁵ CFU/mL after 12 h, indicating that the system still has good physical and chemical stability, extreme pressure carrying capacity and antibacterial stability under short cycle conditions. GH4169 turning validation results show that, compared with the two commercial cutting fluids, the self-developed cutting fluid reduces the maximum tool tip temperature by 13.4% and 8.5%, respectively; reduces the average cutting force by up to 13.5%; increases tool life by 15.4% and 26.5%, respectively; and reduces workpiece surface roughness by 18.2% and 30.3%, respectively. The results indicate that this sulfur-containing water-based semi-synthetic cutting fluid can provide effective cooling, lubrication, extreme-pressure anti-wear protection, and circulation stability during the machining of GH4169. It can serve as a reference for the formulation design and performance evaluation of cutting fluids in the efficient machining of nickel-based high-temperature alloys.