Key Engineering Materials Vol. 522

Abstract: Porous nanocrystalline thick Ti (C_xN_1-x) films which bond firmly to the substrate are obtained on commercially pure titanium and Ti6Al4V alloy by plasma electrolytic carbonitriding (PECN) treatment. The microstructures and compositions of the modified layer on different substrates were compared. The results showed that the modified layer is composed of the outer Ti (CxN_1-x) film and the diffusion layer. When discharge-treated for 150 min, the thickness of the Ti (CxN_1-x) film is ~15μm, irrespective of the different substrate. The TiH₂ riched diffusion layer which is 40-45μm thick is located beneath the Ti (C_xN_1-x) film for the pure titanium substrate, while for Ti6Al4V alloy it is the β-Ti-riched layer which is ~100 μm thick.

Abstract: Considering that the problem of traditional process parameters setting in vacuum casting machine is of long period, high cost and inferior quality stability, a kind of hybrid intelligent decision model which combined with case-based reasoning, neural network and fuzzy reasoning were established. First, use the case-based reasoning technology to extract the similar case from the case database. Then, use the initial parameters to run the mould trial. Finally, use the fuzzy reasoning technology to optimize the initial parameters according to the product defects. Based on the above-mentioned intelligence model, the related hardware and software system was established. The actual practice proved that the system is effective and can be used in practical production.

Abstract: An experimental investigation was conducted on grinding Ti-6Al-4V alloy with monolayer brazed CBN slotted wheels for detecting the performance of the newly developed tools. The results showed that the effects of grinding parameters on the grinding forces and surface roughness with the brazed wheels were similar to that obtained with conventional electroplated ones to a certain extent. However, due to some distinguished features of the brazed CBN tools, i.e., high grain protrusion, optimum grain distribution and especially high joining strength, grain premature pullout behavior that had often occurred for electroplated tools was not observed during grinding, which had significant influence on the CBN wheels with merely singer-layer grains.

Abstract: To investigate the distribution of cutting temperature for surface cutting of nanastructured WC/12Co coating used the PDC cutter, according to machining properties of WC/12Co coating and working conditions, on the basis of the theory of thermal equilibrium of moving thermal source, the mathematical model of temperature field was established through reasonable hypothesis. Simulations were performed for the temperature distribution on the surface and inside the WC/12Co coating specimen using finite element method. And experiment of surface temperature of WC/12Co coating used the PDC cutter was carried out. The finite element simulation results were in good agreement with the experiment data, which verified the validation and capability of the finite element model.

Abstract: The effects of the cutting parameters on residual stresss were investigated in common and ultrasonic vibration hard turning bearing steel GCr15 with PCBN. The residual stresses under the machined surface were measured by X-ray diffraction technique. The results obtained in this study show that residual compressive stress is produced both in common and ultrasonic turning of GCr15 bearing steel. Under the same turning condition the residual compressive produced by the ultrasonic turning is smaller than that by the common turning. Residual compressive stress can improve the fatigue performance and life of workpiece, so the cutting parameters should be optimized to get the best residual compressive stress in ultrasonic turning.

Abstract: A three dimensional quasi-state numerical model of fluid flow ,heat transfer process in the melted pool for composite coating was developed ,and the temperature profile were successfully calculated by finite element software. Numerical results show that when the laser power is 1.5KW, the coating melts and the matrix does not melt, forming good shape; when the laser power is 1.6KW, the thermal stress increase, the binding of substrate and coating occurs crack, the experiment is agreement with that calculated.

Abstract: Using laser cladding technique, TiC reinforced Ti matrix composite coatings were fabricated by preplacing TiC, (Ti+C), (Ti+TiC) powders respectively on the TA2 pure titanium surface.By means of XRD, SEM and Hv-Test, microstructures and microhardness were investigated. The results show that phases of the coatings are all composed of TiC and α-Ti. Delamination phenomenon appears when laser clad pure TiC coating, which has deleterious effect on properties. TiC phase is in-situ synthesized during laser clad (Ti+C) coating, but microstructure is coarse. Microstructure of (Ti+TiC) coating is the most uniform and dense of the three coatings. The microhardness sequence of the three coatings is (Ti+TiC)>TiC>(Ti+C), and the maximum value is Hv1246, Hv1213 and Hv1135 respectively. The main reason leads to the highest micro-hardness of (Ti+TiC) coating is the Ti powder is beneficial to laser cladding and large amount of TiC reinforcement formed which is compact and uniform.

Abstract: In view of characteristics of involute helical gear profile, analyzed the multi-axis machining process for helical gear. Focused on the processing characteristics of helical gear for multi-axis machining, discussed tool path generation, machining program, tool path simulation, cutter interference and collision detection for machine tool and gear profile, seeking out the optimal method and process of helical gear for multi-axis machining. Applying this machining technology in manufacture, it can improve performance of gear, while it can also improve efficiency of manufacture.

Abstract: Polycrystalline Diamond Compact Bit is a new type of drilling tools, which has been developed with the developing of Polycrystalline Diamond Compact Technology. Because of excellent abilities of anti-erosion and shock resistance, PDC bit has higher security and efficiency than rock bit in drilling field [. It has been used more and more in oil drilling and coal drilling, especially, in offshore drilling, ultra-deep drilling and slim-hole drilling [.

Abstract: Wear of diamond tool is also very serious, which affects the surface quality of the machined work material, even if ductile mode where an undeformed chip thickness is at a nanoscale is used. During the cutting process, the crystal structure in the cutting zone is destroyed under the high pressures applied by the diamond tool. The silicon atoms adhering to the tool surface reconstruct to be in a crystal state under the effect of adhesion and pressures.