Applied Mechanics and Materials Vols. 217-219

Abstract: This paper puts forward a new method of surface reconstruction. Power crust algorithm can reconstruct a good surface that is topological valid and be proved theoretically. But when the point cloud is noisy, the surface reconstructed is not good and its running time is long. This paper proposes a improved method of fuzzy c-means clustering to delete the noisy points and a non-uniformly sampling method to resample the input data set according to the local feature size before reconstruction. Experimental results show that the efficiency of the algorithm has been improved much more.

Abstract: Low surface roughness of diamond films is beneficial for the widespread applications in the mechanical field. But brittle ceramic substrate easily forms surface defects, which can be detrimental for surface properties of diamond films. In this work, multilayer technology combining conventional hot filament chemical vapor deposition (HFCVD) is proposed to eliminate the influence of surface defects in the substrate on diamond films. Then multilayer diamond films are deposited on silicon carbide with surface defects by alternately repeating the processes of diamond films growth and surface polishing. Each layer of multilayer diamond films is evaluated by field emission scanning electron microscope (FE-SEM), surface profilometer and Raman spectrum. The results show that multilayer technology is supposed to be a novel deposition method of improving the surface properties of diamond coated the silicon carbide ceramic substrate with surface defects.

Abstract: The surface of pure titanium was coarsened by anodizing. Hydroxyapatite (HA) coatings were electrodeposited on the anodized pure titanium in a simulated body fluid. Complementary characterization methods (SEM, XRD, static contact angle, roughness tester, universal testing) were used to investigate the features of the coatings. The results of this study indicate that porous surfaces can be achieved on the pure titanium by anodizing, and the HA coatings show a relatively regular network structure. Moreover, HA coatings exhibit a certain roughness, good wettability and rather high shear strength.

Abstract: Micro-arc oxidation coating on ZAlSi12Cu2Mg1 alloy were prepared in Na2SiO3 electrolyte, effects of C6H8O7 and C3H8O3 as additive on resistances of micro-arc oxidation coatings were investigated. Results show that coatings containing completest ceramic particles were obtained on alloys surface processed in electrolyte solution including 2.0 g/L C6H8O7 additive, the size of micro-arc wholes becomes larger with more C6H8O7, and it has improved with 1ml/L C3H8O3 in the solution. The results of XRD analysis indicates that the coatings are mainly composed of alumina and mullite. EDS analysis showed the element contains sodium, oxygen, silicon and aluminum. Wear resistance of coating were increased by adding C3H8O3.

Abstract: Ni-TiN-CeO₂ nanocomposite coatings on 45 steel substrate were prepared by ultrasound-pulse electrodeposition. The effects of process parameters, such as CeO₂ and TiN nanoparticles addition, cathode current density, positive pulse duty cycle and ultrasonic power on the Ni-TiN-CeO₂ nanocomposite electrodeposition process were studied by orthogonal experiments. The nanoparticles contents in the coating were determined, and the surface morphology of the coating was analyzed. The results show that the optimized process parameters are: the CeO₂ particles addition of 40g/l, the TiN particles addition of 15g/l, cathode current density of 4A/dm², positive duty cycle of 20%, and the ultrasonic power of 180W. Under the optimum condition, the desirable Ni-TiN-CeO₂ nanocomposite coatings are prepared with higher particle content and better surface quality.

Abstract: The control system of vertical tin-plating for semi-flexible coaxial cable was introduced in this present paper. The control objects of this control system included the molten tin temperature, the immerging depth and the feeding speed of the cable. In this control system, the feeding speed of the cable was controlled and displayed in range of 2~22 m/min. The lifting metal box driven by a motor was used to control the immerging depth. The immerging depth and time of the cable in the molten tin solder was controlled in 10~100 mm and no more than 3 sec, respectively. Using two thermocouples could reduce the measurement error caused by uneven distribution of molten tin temperature in the tin tank. The control range of molten tin temperature was about 100~400°C. The tension detecting device ensured the tension of the cable in a suitable range. A smooth and continuous tin coating on the outer conductor was obtained at the cable speed 4~6 m/min, the immerging length 40~80 mm, the immerging time 0.5~1 sec and the molten tin temperature 255~265°Cwith this control system.

Abstract: This paper presents a new approach of tool deflection error regularization and compensation in end milling of contour surfaces. The material removal rate (MRR) is adopted as the dominant factor of surface dimensional error. A mathematics model of determining the MRR in generalized contour surfaces machining is proposed. Feedrate scheduling methodology is applied to regulate a constant MRR along curved tool path. The expectation with the constant MRR is that it will potentially produce a constant surface dimensional error. Thus, the compensation can be conveniently achieved by offsetting the nominal finishing path. The desired MRR and corresponding offsetting value of finishing tool path are determined by a peripheral milling test. Machining results obtained in this study reveal that the proposed approach can significantly reduce the surface dimensional error and the smooth variation of feedrate can get a few variation of surface dimensional error. Comparing to the existing methods, the time-consuming iterative process in error compensation is omitted.

Abstract: Abstract. FeCrAl/aluminum bronze composite coatings were prepared by supersonic electric arc-spraying. The microstructure of the composite coating was studied by using optical microscope (OM), scanning electron microscope (SEM). The results show that the FeCrAl and QAl7 aluminum bronze composite coatings have a typical layered structure which is composed of FeCrAl, QAl7 aluminum bronze flattened particles as well as alumina films between them. FeCrAl and QAl7 aluminum bronze flattened particles are distributed alternately and have a good combination btween each other.

Abstract: In this paper, the pure MCrAlY coating and nano-Al₂O₃ particles reinforced MCrAlY graded coating were prepared on TiAl base intermetallic alloy substrates by laser cladding process. Furthermore, the microstructure characterization, microhardness and wear resistance of the two kinds of MCrAlY coating were comparatively investigated with scanning electron microscope (SEM), HXD-1000TC hardness tester and MM-200 block-on-ring dry sliding wear tester. The results show that the laser-clad pure MCrAlY coating has a dendrite crystals characteristic. However, the graded composite MCrAlY coating consists of fine equiaxed grains because of addition of nanometer ceramic particles. Moreover, the grain size becomes small with increasing the nano-Al₂O₃ content in the coating. The microhardness and wear resistance of the composite coating is higher than that of the pure coating. The mainly wear mechanism of the pure MCrAlY coating is abrasive and delamination, while the mainly wear mechanism of the composites graded MCrAlY coating is abrasive.

Abstract: Ti-6Al-4V, C and TiB2 powders (71.5%Ti-6Al-4V+ 26.2%TiB2+2.3%C in wt. %) were prepasted and then laser clad on Ti-6Al-4V substrates. Laser cladding was carried out with a Nd:YAG pulse laser with the parameters of defocus length 15mm, pulse frequency 15Hz, scanning speed 2-4mm/s, electric current 200-240A. Microstructure and phases were analyzed with the Optical Microscopy(OM), Scanning Electron Microscopy(SEM) and X-Ray Diffraction(XRD). Laser cladding layers with smooth surfaces, good metallurgical bonding with no cracks and pores were formed. The average thickness of the coatings is approximately 80μm. Reactions among Ti, C and TiB2 in the laser molten pool cause in-situ synthesis of TiB, TiB2 and TiC reinforcements. The average microhardness is 836HV, which is more than twice that of the Ti-6Al-4V substrate (320HV). Friction coefficients of the cladding coatings fluctuate between 0.26-0.3. Laser cladding specimen with powder mixture of 71.5%Ti-6Al-4V+ 26.2%TiB2+2.3%C (weight loss 0.0007g after sliding 245m) possesses better wear property than that of the specimen with powder mixture of 90%Ti-6Al-4V+ 10%B4C (weight loss 0.0068g).