Jian Xin Deng

Research and Development of High Speed Cutting Tribology

Due to large deformation, high pressure and high temperature, the tribological behavior between tool and workpiece in high speed cutting is markedly different from that between mechanical parts. High speed cutting tribology is a interdependent scientific discipline, in which kinematics and friction between tool and workpiece, tool wear and fracture, match of mechanical, physical and chemical properties of materials between tool and workpiece, as well as influences of cutting conditions and external environment (such as air, cutting fluids) on tribology and machined surface are investigated. The discipline of high speed cutting tribology is the science base for tool materials design and predicting the tool life, surface integrity and cutting accuracy for high speed cutting. In this paper, the concept of high speed cutting tribology and its research development and prospect are presented.

Influence of the Deposition Temperature on the Properties of Medium-Frequency Magnetron Sputtering WS2 Soft Coated Tools

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.

Friction and Wear Behavior of Textured Al2O3/TiC Ceramic Surface Filled with MoS2 Solid Lubricants

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.

Experimental Study on the Cutting Temperature with Micro-Texturing Self-Lubricated Tools

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.

Oxidation Resistance of CrN and CrAlN Coating Tools

CrN and CrAlN coating tools were heated and heat-preserved in electric stove to make oxidation experiment. The results were obtained through SEM, EDX and XRD. The results are as follows: The oxidation of CrN and CrAlN coating is induced by the micro-holes which were formed by the diffusion of nitrogen atoms and chromium ions towards the coating surface under sufficient thermal energy. With the incorporation of Al, CrAlN coating showed stronger oxidation resistance as compared to CrN. The dense mixture of Cr2O3 and Al2O3 makes oxygen diffusion through the film difficult and then oxidation and decomposing are alleviated effectively, therefore CrAlN coating can remain high oxidation resistance and high hardness after high temperature which make this coating tool be competent for high speed machining of the hardworking materials. In addition, the failure of the coating is primary induced by oxidation and the different expansion coefficients between coating and substrate.

Erosion Wear Behavior of Coatings with Growth Defects Produced by Ion Beam Enhanced Pulsed Filtered Vacuum Arc Deposition

The erosion wear behavior of TiN coatings with growth defects was studied. The TiN coatings were produced on a hard metal by ion beam enhanced pulsed filtered vacuum cathode arc deposition. The erosion wear was tested with a gas blast apparatus. In the test, TiN coatings were impacted at an impingement angle of 90° by angular SiC solid particles with an average diameter of 124um. The maximum depth of the erosion scar measured by the optical profiler was used to evaluate the erosion wear loss of the coatings. The coatings proved to have much lower erosion rate than that of the substrate material and consequently, the erosion rate increased significantly to the high level of the hard metal substrate after the coatings were penetrated. The failure mechanism was revealed by examining the surface morphologies of the coatings before and after the erosion test. The erosive wear of the TiN coatings with growth defects behaved as typical brittle materials. The damage mechanism of the coatings with growth defects was described.

Friction and Wear Behaviors of Three Ceramic Composite

Three ceramic composite were prepared by hot pressing sintering. The friction and wear behaviors of the composite were experimented at the high speed wear and tear test machine. Results show that the three ceramic composite have strong fracture toughness and flexure strength. The wear mechanisms of three ceramic composite are mainly brittleness peel off and furrow. Al2O3/(W, Ti)C and Al2O3/SiCw ceramic composite have great capabilities in wear resistance; they are excellent materials of cutting tools and dies.

Virtual Design Technology of Piston Production Line Based on Lean Production

Facing fierce global competition, companies must adjust the production line according to Lean Production, especially in piston field. In order to get a p roductive and rational production line rapidly and effectively, a virtual design method with virtual manufacturing was introduced. First, the production line based on Lean Production was analyzed. Secondly, the key technologies to virtual design were described: planning the virtual production line, establishing the basic resource class library, and simulating the virtual production line. At last,a virtual piston production line is presented, built and simulated in QUEST.This method will provide an efficient tool for the layout planning and rapid reconfiguration design of piston production line, realize the Lean Production goal.

Erosion Wear Resistance of CWS Laminated Ceramic Nozzles

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.

Friction and Wear of Typical Tool Material at Elevated Temperature

The friction and wear behavior of cutting tool materials keeps an issue. In this study, an high temperature tribometre (UMT-2) was used to investigated the tribology properties and mechanism of two kinds of typical cutting tool materials. Commonly used cemented carbide (ZU5) and ceramic (AT) were chosen. The characteristics as to wear rate, friction coefficient and worn surface were studied. From the results, we found that the ceramic had better wear resistance than the cemented carbide. The friction coefficient of cemented carbide decreased with the increase of ambient temperature while the ceramic exhibited an inverse tendency. Finally, the probable wear mechanism was discussed.