Experimental Research On Friction And Wear Of Mirror Die Steel In Cold Plasma Jet

Mirror die steel, as a kind of hard-to-cut material, has several problems, such as big cutting force, high machining temperature and work hardening in the process of machining. The cold plasma jet assisted cutting is a kind of machining method, which sprays the atmosphere air cold plasma jet to the cutting area as lubrication and cooling medium. If used in the process of machining mirror die steel, the lubrication and cooling effects of cold plasma jet can attain or play a better effect than that of cutting fluid in machining hard-to-cut material. At the same time, it is environmentally friendly. So this cutting method has a broad application prospect.Based on the analysis of hard-to-cut material and the present state of cold plasma jet, the friction-wear test of friction couple in cold plasma jet environment by using self-designed equipment is studied in the paper, providing foundation for further study of cutter wear properties in cold plasma jet assisted cutting mirror steel. The main work of this paper is as follows:In order to confirm the suitable ionized air discharge form and generation condition of cold plasma jet, the generation method of atmosphere cold plasma jet and the function mechanism of cold plasma jet assisted cutting were studied on the basis of analyzing general characteristic of air discharge. The results prove that the corona discharge have many advantages such as low macro temperature, simple electrode structure and easy operation. What’s more, a high ionization degree and uniform jet are gained when pin-cylindrical bare electrode pole is applied. All these indicate that the corona discharge is a suitable air discharge form for cold plasma jet assisted cutting. Based on the aforementioned study, a nitrogen cold plasma jet generation equipment of pin-cylindrical bare electrode was built to produce stable jet.The jet size was as evaluation standards to analyze the rules of discharge parameters affecting on cold plasma jet. The results prove that big size nitrogen cold plasma jet is obtained when nitrogen flow q is1.0m3/h, nozzle diameter D is4mm and the needle tip to the nozzle exit distance h is2.5mm.In order to study anti-friction effect and mechanism of mirror die steels machined by cold plasma jet, typical mirror steel S136-YG8and NAK80-YG8friction pairs were studied in air, nitrogen jet, and nitrogen cold plasma jet atmosphere, respectively. The friction surface morphology and constituent are analyzed by SEM and EDS. The function rule and mechanism of anti-friction of cold plasma to mirror die steel are also studied. The experiment results show that the nitrogen plasma jet can reduce friction coefficient of S136-YG8and NAK80-YG8friction pairs, decrease abrasive wear and adhesive wear of S136-YG8, decrease abrasive wear and oxidative wear of NAK80-YG8.