Papers by Author: Jian Xin Deng

Abstract: Textured self-lubricated tools were designed and fabricated. Dry cutting tests were carried out on with these self-lubricated tools and a conventional tool. The tool wear and the friction coefficient at the tool chip interface were measured. It was shown that the tool wear and the friction coefficient of the textured self-lubricated tools were reduced compared with that of the conventional tool. Two mechanisms responsible were found, the first one is explained as the formation of a lubricating film with low shear strength at the tool-chip interface, which was released from the texturing and smeared on the rake face, and served as lubricating additive during dry cutting; the other one was explained by the reduced contact length at the tool-chip interface of the textured tools, which contributes to the decrease of the direct contact area between the chip and rake face. It is suggested that the using of textured self-lubricated tools is an effective way to reduce the tool wear in dry cutting.

Abstract: The paper reports the tribological properties of the CrAlN coating tools at different speeds and loads. The coating was deposited on cemented carbide by cathodic arc physical vapour deposition technique. Ball-on-disc wear tests were performed on the CETR UMT-2 test system against SiC balls. The coating character and test results were obtained through SEM, XRD and Wyko surface profilometer. The results are as follows: The value of friction of coefficients decreased and depth of wear tracks became sallower as speeds increased and the coating presented adhesion phenomenon under low load. CrAlN coating showed excellent anti-wear properties at high speed and low load, and was more suitable for these similar working conditions.

Abstract: Three different textures were produced by Laser Surface Texturing (LST) on Al₂O₃/TiC ceramic surfaces. MoS₂ solid lubricants were filled into the textures. The friction and wear properties of textured and untextured surfaces were investigated by carrying out sliding tests against AISI440C stainless steel balls. Results showed that the textured surfaces filled with MoS₂ solid lubricants exhibited lower friction coefficient and excellent anti-wear properties compared with untextured surfaces. At the texture spacing of 100μm, 150μm and 200μm, wavy textured surface had the lowest friction coefficient, while it was the dimpled surface at the texture spacing of 250μm. MoS₂ film in the spaces between the textures was formed by mechanical engagement of particles in the rough surfaces and solid lubricants in textures. The friction coefficient and wear rates were reduced by supply of solid lubricants from the textures to the surfaces, bulges around the textures and TiO₂ formed after laser texturing.

Abstract: WS₂ soft coatings were deposited by medium-frequency magnetron sputtering, multi-arc ion plating and ion beam assisted deposition technique on the YT15 cemented carbide substrates. The influence of the substrate bias voltage on the coating properties has been studied. The coatings exhibited a dense and fine grained structure. WS₂ soft coatings with substrate bias voltage of -100 V revealed a better coating properties than other four samples, as the best crystallization of (002) preferred crystal orientation of Ⅱ texture, the most smooth and uniform microstructure of the coating, the largest critical load of 43.25 N and the largest coating thickness of 1.5 μm. But the microhardness of sample S1 was only 515.4 Hv. The critical load and the thickness of WS₂ coatings decreased firstly, then increased, and finally reduced with the increasement of substrate bias voltage. And the microhardness of the coatings decreased firstly, then increased, and decreased, finally increased with the increasement of substrate bias voltage.

Abstract: In coal-water-slurry (CWS) boilers, the nozzle is eroded continuously by the abrasive action of the CWS, and there are high temperature and temperature gradient inside nozzle, which may cause large tensile stress and lead to an increased erosion wear of the nozzle. In this paper, Al2O3/(W,Ti)C+Al2O3/TiC laminated ceramics were developed to be used as nozzles in CWS boilers. The purpose is to reduce the tensile stresses at the nozzle during the CWS burning process. The value of the residual stresses, which arise from a mismatch between the coefficients of thermal expansion of the constituent phases and neighbouring layers, was calculated by means of the finite element method. The erosion wear behavior of the laminated nozzles was investigated and compared with an unstressed reference nozzle. Results showed that the laminated ceramic nozzles exhibited an apparent increase in erosion wear resistance over the unstressed reference one. It is suggested that laminated structures in ceramic nozzles is an effective way to improve their erosion wear resistance in industrial CWS boilers.

Abstract: Oil suspension was made with different concentrations of SiO₂ particles.The effects of SiO₂ with different concentrations on frictional pairs 45# -PTFE under different velocities is investigated on MRH-3 abrasion tester. The worn of PTFE surfaces was investigated by scanning electron microscopy (SEM).The results show that the friction coefficient increases with increasing SiO₂ concentrations. The wear rate increases with the increasing particle concentration and then decreases a bit. Meanwhile the degree of wear increases with increasing particle concentrations. Furthermore, as shown in SEM micrographs, the main machenism of PTFE is furrowing wear.

Abstract: WS₂ soft coated tools were deposited by medium-frequency magnetron sputtering, multi-arc ion plating and ion beam assisted deposition technique on the YT15 cemented carbide substrates. The influence of the deposition temperature on the coating properties has been studied. The coatings exhibited a dense and fine grained structure. WS₂ coatings revealed a (002) preferred crystal orientation. WS₂ soft coatings with deposition temperature of 200°C revealed a better crystallization of (002) preferred crystal orientation of Ⅱ texture than other three deposition temperatures. And the adhesive strength could get to 43.25N which was the largest. The thickness of WS₂ coatings decreased firstly, then increased, and finally reduced with the increasement of deposition temperature. And the microhardness of the coatings increased firstly, then decreased, and finally increased with the increasement of deposition temperature.

Abstract: The friction and wear behaviors of Al₂O₃/TiC ceramic tool materials were evaluated at temperature up to 800°C. The friction coefficient and wear rates were measured. The microstructural changes and the wear surface features were examined. Results showed that the temperature had an important effect on the friction and wear behaviors of Al₂O₃/TiC ceramics. The friction coefficient decreased with the increase of temperature, while the wear rates increased with the increase of temperature. The difference of the worn surface features of the Al₂O₃/TiC ceramics at different temperature is related to the chemical transformation during sliding wear tests. The wear mechanism of the composites at temperature less than 400°C was primary abrasive wear, and the mechanisms of oxidative wear dominated in the case of 800 °C sliding operation.

Abstract: In some circumstances, huge mass, if not cushioned, may pull the piston to a halt at rod side or head side at ease with a tremendous velocity causing huge impact. As a result of this issue, the boom cylinder of hydraulic excavator provides cushioning apparatus at the rod side stroke end. This paper discusses and analyses the cushioning apparatus structure of boom cylinder, and then proposes a numerical simulation model with SimulationX. It is known to us that many dynamic parameters of boom cylinder vary as mechanical structure or motion of excavator attachment changes. Thus in order to study the relationship between kinetic parameters and cushioning capability of boom cylinder, an excavator attachment model is built next. The last part of this paper is devoted to the obtained simulation results.

Abstract: Micro-texturing self-lubricated cutting tools named MTR-1 and MTR-3 were designed and made based on micro-texturing lubricating idea and laser micro-texturing technology. Dry cutting tests on 45^# hardened steel were carried out with these self-lubricated cutting tools and conventional cemented carbide tools named MT0. The cutting temperatures and the morphology of chips were measured. The results indicated that the cutting temperatures with the micro-texturing self-lubricated cutting tools were reduced compared with that of MT0 cemented carbide tools, and the chip coiling was improved.