Authors: Zhen Bing Cai, Min Hao Zhu, Xiu Zhou Lin, Ji Liang Mo, Zhong Rong Zhou
Abstract: Nickel base Ni60 and cobalt base Co-Cr-W coatings were prepared on substrate of
refractory alloy steel 4Cr14NiW2Mo by laser-cladding technology. A 2 kW transverse-flowing CO2
laser device was used for cladding alloy powder. Another Co-Cr-W coating was formed by bead
welding. Under room temperature, 250 oC.and 420 oC, reciprocate sliding wear tests with a
ball-on-flat contact for three coatings have been carried out. For the laser cladding coating, a good
metallurgical bonding with the substrate was obtained. Different tribological behaviors of three
coatings were observed. For the two Co-Cr-W coatings, the friction coefficients decreased with the
increase of test temperature, and larger spot-like stripping pit and wider ploughing trenches in the
wear scars were presented. The wear mechanism was the combination of abrasive wear,
delamination and oxidation wear. For the Ni60 laser cladding layer, the friction coefficient hardly
changed with the elevated temperature, and the wear mechanism mainly performed as abrasive wear
due to its high oxidation resistance. The wear tests showed that the Ni60 clad coating had provided
excellent wear resistance than Co-Cr-W layers under high temperature reciprocating sliding wear
condition.
878
Abstract: The current study using ultrasonic energy transmitted into the electrolyte to assist in
discharging of electrolytic product and cuttings out of the machining gap in the synchronous finish
processes of grinding and electrochemical finishing on hole-wall surface beyond traditional process
of holes machining instead of conventional hand or machine polishing. The design finish-tool
includes a grinding-tool and an electrode as a hole-wall surface finish improvement that goes beyond
traditional rough boring. In the experiment, the finish-tool is completely inserted to the hole; the
electrode is used with continuous or pulsed direct current. The electrode form and the machining
process are obviously different from electrochemical grinding (ECG). The experimental results show
that the large supply of current density is effectively to reach the amount of the material removal and
is advantageous to the finish processes. The finish effect is better with a high rotational speed of the
finish-tool because the dregs and cuttings discharge of electrochemical finishing and grinding
becomes easier and is also advantageous to the finish. The average effect of the ultrasonics is more
better than the pulsed current while the machining time needs not to be prolonged by the off-time. The
synchronous processes of grinding and ultrasonic electrochemical finishing just require a short time to
make the hole-wall surface smooth and bright.
295
Authors: Hua Feng Zhang, Yu Zhong Zhang, Li Gang Lin, Xiao Li Ding, Hong Li
Abstract: Polyvinylidene fluoride (PVDF) hydrophobic membrane has been prepared by phase inversion method. The effects of concentration of PVDF, different processes of preparations, and different surface roughness on hydrophobic capability of membrane surface (water contact angle, WCA) have been investigated. The results showed that, hydrophobic ability of PVDF membranes decreased with the increasing concentration of PVDF. WCA of membrane prepared by was increasing. Membrane surface hydrophobic ability increased with the increasing surface roughness. The contact angle of membrane comes to 141° with dry process and 10% PVDF concentration.
338
Authors: Hao Zhang, Jian Song, Ming Cong
Abstract: Machining simulation can quick supply valuable data to help improving machine processing quality and efficiency. And it is playing an important part in the development of modern machining theory. In this paper, the drilling process of an engine block was simulated in the software of DEFORM-3D. The geometry models of cutter and workpiece were simplified to avoid too low efficiency of simulation running. The mesh weight factors were specified to keep geometry models from changing too much from the real situation. 11 simulation experiments were carried out. And through regression analysis of the result data, the drilling load formulas were obtained to predict the axial force and moment in the drilling process of engine block.
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