Research On Ultra-Precision ELID Grinding Technology Of TN85 Cermet Spherical Coupling

TiC cermets have excellent wear resistance, oxidation resistance, corrosion resistance and mechanical properties. It is not only used as tool materials successfully, but also can be applied in drawing mode, various engine parts under high-temperature and seals in petrochemical industry. TN85 cermets is one kind of composites, in which nickel alloy is binder and the hard phase is TiC, WC. TN85 with the excellent high hardness, high toughness, high bending strength, good wear resistance has a good extensive application prospect in corrosion and wear areas.At present, the research of metal-ceramic is focus on the sintering technology and the application-oriented friction and wear properties, however there is less research on ultra-precision machining mechanism and technology of cermets. So the research on the technology and ultra-precision machining mechanism of cermets is becoming increasingly urgent and important. Most of the existing processing methods can not be applied to the ultra-precision machining for the matching parts with small curvature radius concave spherical surface by limit of process conditions, therefore it is an important problem that the ultra-precision machining for the matching parts with small curvature radius concave spherical surface. It has the important significance for the development of new the ultra-precision machining technology for the matching parts with small curvature radius concave spherical surface.ELID (Electrolytic in process dressing) grinding technology with simple installation, low cost, portability and good features is the key technology to of ultra-precision grinding, and it has been studied in many countries extensively. In this paper, ELID grinding of non-specific electrode technique is a new method for TN85 cermets to machining small curvature radius concave spherical surface. It is an exploratory research, and this specific study includes:The general status of grinding removal mechanism for cermets, the experimental study of grinding removal for cermets, ELID (Electrolytic in process dressing) grinding technology and in both domestic and overseas is reviewed. ELID grinding without special electrode for the matching parts with small curvature radius concave spherical surface is developed.The grinding removal mechanism for cermets has been studied. During the process of the removal of TN85 cermets, the embossed mechanism is formed by material composition characteristics of TN85 cermets. It is difficult to achieve the ultra-precision level for most of the existing processing methods because of the embossed mechanism, however, the "uniform" removal of soft and hard phase can be realized by ELID grinding technique.The composition characteristics of TN85 cermets and the process of grinding removal are studied, and the removal model of TN85 cermets during grinding is developed. At last, the model is validated by the analysis of the surface micro-morphology of TN85 cermets after grinding. On the basis of the grinding removal mechanism of TN85 cermets, the basic study of the Indentation experiments, the characterization experiments of single-particle diamond and the grinding removal mechanism of micro power diamond grinding wheel has been conducted. Through basic experimental research, the hardness material properties and the characteristics of material grinding removal, the grinding removal mechanism of TN85 cermets has been verified and interprted.On the basis of the analysis of traditional ELID Grinding, ELID grinding intermittent electrolytic dressing, ELID grinding uses workpiece as dressing electrode, ELID grinding technique without special electrode is proposed to grind the matching parts with small curvature radius concave spherical surface. The study of the ELID grinding technique without special electrode is conducted, and the applied research on grinding experiments in which concave spherical parts is used as dressing electrode. The feasibility of ELID grinding technique without special electrode on the grinding of the matching parts with small curvature radius concave spherical surface is confirmed by above research, and it is the basis of the further applied research.The effects on both spherical degree and surface roughness in the ELID grinding technique without special electrode for the matching parts with small curvature radius concave spherical surface by two processing parameters. The results show that: The installation and adjustment precision of grinding machine is the main factor for spherical degree error and spherical diameter error, and the Granularity of micro power diamond grinding wheel cast iron base and the species of the bond is the main factor for surface roughness. The basis of follow-up popularization and application of the ultra-precision machining for particle reinforced metal matrix composites has been set up by the error analysis. The concave spherical surface of the TN85 cermets workpiece, the diameter of which is 12mm, is machining by intermittent ELID grinding use workpiece as dressing electrode, and after grinding the roughness Ra is 23.4nm.