Key Engineering Materials Vols. 336-338

Abstract: The composite zirconium silicate microbeads with different pretreating process were developed in this paper. The wear loss of these microbeads was compared by testing of agitation mill. These microstructures with different micro-pores were compared by scanning electron microscopy. The pore size was found have obvious influences on the mechanism of the wear. Some solutions were proposed to overcome the micro-pores in the zirconium silicate composite microbeads.

Abstract: The TiC particles are selected as reinforced phase and the Hadfield steel as matrix. The powder metallurgy liquid phase sintering technique is adopted to fabricate TiC particles reinforced Hadfield steel matrix composites. The effects of elements Mo and Ni on the performance of the composites were studied. The impact wear tester is adopted to investigate the wear-resistant property of the composites under the different impact loads. Adding Mo can improve the interfacial bonding between the Hadfield steel and TiC, and the best adding ratio between Mo and TiC is 1:3.68. Adding 2%(vol.%)Ni can significantly improve the density and hardness of the composites. The experiment results of impact wear tests show that under the condition of low and middling loads, the composites display the best wear-resistant properties, moreover, the more TiC content is, the better wear-resistance property is. Under 2.0J impact energy, the wear resistance of the composite containing 40%(vol.%) TiC is 1.3 times of Hadfield steel.

Abstract: Copper film was plated on Al2O3 ceramic powder in Al2O3 ceramic with copper matrix. The influence of copper film plated on Al2O3 ceramic powder to friction coefficient and amount of wear has been studied in this paper. Variance analysis shows that copper film on Al2O3 ceramic powder does not have significance influence to friction coefficient, but has significance influence to amount of wear of Al2O3 ceramic with copper matrix. Amount of wear of Al2O3 ceramic with copper matrix decreases with the increase of copper film plated on Al2O3 ceramic powder initially. When the copper film plated is beyond 47%, The amount of wear reaches a stable volume, and almost does not reduce again with the increase of the copper film plated on Al2O3 ceramic powder. To Al2O3 ceramic with copper matrix in this paper, the optimum copper film plated is 47%.

Abstract: The correlation between machining performance and mechanical properties of Y-TZP/Al2O3 ceramics with different mechanical parameters was investigated. The grinding experiments indicated that the flexural strength had a definite influence on machining performance of samples. The higher the flexural strength was, the more difficult the sample was to be ground. XRD analysis showed that an increasing amount of the monoclinic ZrO2 would reduce the flexural strength of the samples. As a result, the grinding force that the samples underwent also decreased.

Abstract: The compressing piston and cylinder of refrigerating compressor frequently come into failures as anti-wearability for metal material is weak. Engineering ceramics is appreciated by designers thanks to its excellent performances. However, it is difficult to machining material because of high hardness. The FEA modules for displacement and stress distributions of compressing piston and cylinder under declared running conditions are established based on the theories of elasto-plasticity and aerodynamics, which reveal the optimal precision conjugation clearance dependence of pressure distributions regularity between friction couple. Based on the FEA analytical results, the feasibility of replacing metal material with Si3N4 ceramics in the friction couple manufacture is researched. Special clamps have been designed to guarantee the superficial quality as mirror surface and tolerances of form and position, technological procedures are programmed, and with satisfactory machining effect.

Abstract: Advanced ceramics has many advantages and great potential of application, but its high machining cost resulted from its high hardness and brittleness limited its application. Grinding with superabrasives is the most suitable and effective way for machining of advanced ceramics. Grinding with vitrified bond CBN wheels is a developing direction of high efficient grinding for engineering ceramics. Grinding of the promising composite ceramics of TZP/Al2O3 with vitrified bond CBN grinding wheels was investigated in this paper. The results showed that higher material removal rates and satisfactory surface finish were achieved, CBN wheels with coarser grit size or with higher CBN concentration had higher grinding ratio. G-ratio increased with the increasing of wheel speed.

Abstract: An experimental investigation is carried out to machine SiC ceramic material through method of high speed plane lapping with fixed abrasive. The results show that the material removal mechanism and the surface roughness are chiefly related to the granularity of abrasive and the lapping pressure for the brittle materials such as SiC ceramic. It is easily realized to machine SiC ceramic material in ductile mode with a high efficiency and a low cost using W3.5 grit under a lapping pressure of 0.1MPa and then a smooth surface with surface roughness of Ra 2.4nm can be achieved.

Abstract: The machinable fluorophlogopite was drilled with tungsten-cobalt carbide and high-speed steel drill bits, respectively. The wear widths of major flank were measured, and the wear characteristic of twist was analyzed during drilling fluorophlogopite ceramics.Drilling experiments were carried to consider influence factors of drill bit wear, such as tool materials, cooling condition, spindle speed and tool angles. Tool materials and cooling conditions are the major factors to affect wear of drill bits. High-speed steel drill bits are not suitable for drilling fluorophlogopite ceramics. Cooling condition affects wear remarkably. With the rising of spindle speed, the wear widths of major flank grows. But apex angle has little affects on the tool wear rate. Research results indicate that low tool wear can be obtain through optimizing tool material and machining parameters in drilling fluorophlogopite ceramics.

Abstract: In this study, grinding of Si3N4, SiC, and Al2O3 ceramics under the condition of electrolytic in-process dressing (ELID) system was investigated. The surface appearances of these engineering ceramics during the ELID grinding process were attentively observed to describe the formation of finely finished surfaces. Based on the analysis of material properties and detailed micro-observation of ground surfaces, it can be concluded that the material removal mechanism of engineering ceramic is closely related to its mechanical properties. The silicon nitride ceramic was most easily machined to precision surface among these three engineering ceramics.