Effect of water in oil emulsion on the surface quality of Inconel 718 alloy during coupling electrical pulse and ultrasonic treatment

A new kind of water in oil (W/O) emulsion with 40 wt% of water content is developed and applied to the coupling electrical pulse and ultrasonic treatment (CEPUT) of Inconel 718 alloy. After treatment, a strengthening layer of about 450 μm is produced on the surface, the surface hardness reaches 503.8 HV, and the surface roughness Ra is reduced to 0.042 μm, reaching a mirror surface. The role of the W/O emulsion in CEPUT is analyzed, and it is found that 40% (wt% of water content) W/O emulsion can suppress the discharge between carbon brush and the sample surface, and effectively reduce the surface discharge pits. At the same time, it can provide an excellent lubrication effect, reducing the “harmful” tangential plastic deformation caused by friction, and a better surface effect can be obtained. In addition, compared with water, 40% W/O emulsion weakens the impact damage of cavitation on the sample surface and reduces the pits caused by impact. After CEPUT with 40% W/O emulsion, the average friction coefficient of the sample surface is reduced by 22.3%, and the wear amount is reduced by 43.2%. [Display omitted] •A novel water in oil emulsion is developed for coupling electrical pulse and ultrasonic treatment of Inconel 718 alloy.•The surface roughness Ra is reduced to 0.042 μm while strengthening the surface of Inconel 718 alloy.•The wear resistance of the metal surface is improved, and the wear amount is 43.2% less than that before treatment.