Guanghong Zhou

Structure and Mechanical Properties of Ni-P-Nano Al2O3 Composite Coatings Synthesized by Electroless Plating

Ni-P-nano Al2 O3 composite coatings were deposited by electroless plating, and their microstructures were observed by SEM (scanning electron microscope). The microhardness and the wear resistance of the Ni-P-nano Al2 O3 composite coatings were measured using microhardness tester and block-on-ring tribometer, respectively, and the comparison with those of Ni-P coatings or Ni-P-micro Al2 O3 coating was given. The influences of aging temperature on their hardness and wear resistance were analyzed. The results showed that the nano Al2 O3 particles were distributed uniformly in the Ni-P-Al2 O3 coatings. Among three kinds of Ni-P based coatings, the hardness and wear resistance of Ni-P-nano Al2 O3 coatings were largest, and the maximum values could be obtained at 400 °C. This indicated that the precipitation of nano Al2 O3 particles would improve the hardness and wear resistance of the Ni-P coatings.

Improvement of adhesion properties of TiB2 films on 316L stainless steel by Ti interlayer films

Abstract The periodic [Ti/TiB 2 ] n ( n =1, 2, 3) multilayered films were prepared on the substrate of AISI 316L stainless steel by magnetron sputtering to enhance the adhesion of TiB 2 films based on the remarkable mechanical performance of layered films. The influence of periods on microstructure, adhesion and hardness of [Ti/TiB 2 ] n multilayered films was studied. X-ray diffraction (XRD) analysis shows that the monolayer TiB 2 films exhibit (001) preferred orientation, and the preferred orientation of [Ti/TiB 2 ] n multilayered films transfers from (001) to (100) with the increase of periods. The cross-sectional morphology of each film displays homogeneity by field emission scanning electron microscopy (FESEM). The hardness of the films measured via nanoindention changes from 20 to 26 GPa with the increase of periods. These values of hardness are a bit lower than that of the monolayer TiB 2 films which is up to 33 GPa. However, the [Ti/TiB 2 ] n multilayered films present a considerably good adhesion, which reaches a maximum of 24 N, in comparison with the monolayer TiB 2 films according to the experimental results.

Dry sliding friction behavior of copper–matrix composites by self-propagating high-temperature synthesis

This paper presents a simple approach to preparing copper–matrix composites (CMCs) by using self-propagating high-temperature synthesis technique. The dry sliding friction behavior of CMCs was systematically investigated. Results showed that the strengthening layer presented a compact metallurgical joint to copper substrate without a distinct boundary. The running-in period for copper substrate at any load was approximately 125 s but decreased to less than 30 s for CMCs. Increasing the applied load resulted in shorter running-in periods. The average friction coefficients for pure copper substrate and CMCs presented slight variation at the steady state, with minor enhancement in CMCs. The wear loss rates of the two different sections in CMCs rapidly increased with increased load, and the wear loss rate of CMCs was always lower than that of pure copper substrate at any load. Typical adhesion wear character was observed according to the wear scar of pure copper substrate; the wear mechanism of CMCs was dominated by abrasive wear, accompanied by oxidized wear with increased applied load.