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The mechanical properties and tribological behavior of ductile iron tempered at different temperatures were investigated. The tempered sample was composed of spheroidal graphite, α phase, and carbides. The strength and hardness decreased near-linearly but the plasticity increased with the increase of tempering temperature, which was mainly because carbon atoms precipitated from martensite and thus reduced the distortion of martensite. Wear tests indicated that the friction coefficient of the sample tempered at 420 °C decreased first and then increased with the increasing loads and exhibited the lowest friction coefficient of 0.37. No obvious change was detected for the friction coefficient of the sample tempered at 500 °C at different loads. The friction coefficient of the sample tempered at 580 °C increased to a stable value with the increase of loads. The wear rate of tempered ductile iron was increased with the increase of tempering temperature, which indicated that hardness was the critical factor for wear properties of ductile iron. The main wear mechanisms of tempered ductile iron were adhesive and abrasive wear. Adhesive wear was predominant for the sample tempered at low temperature but was gradually replaced by abrasive wear with the increase of tempering temperature and normal loads.

TiSiN-Ag composite coatings with different Si doping contents were prepared by multi-arc ion plating technology on 316L, TC4, and H65 copper substrates, respectively. The microstructure of the prepared coatings was characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy, respectively. The mechanical properties, electrochemical properties, and tribological properties were characterized by a micro-hardness tester, electrochemical workstation, scratch tester, and friction and wear tester, respectively. Results showed that the coatings with 8 wt.% Si doping content had a smaller average grain size, denser structure, excellent mechanical properties, and better anti-tribocorrosion performance than those with 5 wt.% Si doping content. The coating on the TC4 substrate with 8 wt.% Si doping content presented the best combination of properties and is a candidate for an anti-tribocorrosion material in seawater.

Amorphous Al2O3 coating with a thickness of 143 &mu, m was firstly prepared by anodic oxidation, then the amorphous Al2O3 was transformed into crystalline Al2O3 through applying micro arc discharge. The crystal structure of the Al2O3 coatings was analyzed with an X-ray diffractometer. Results indicated that the coating consisted of amorphous and crystalline Al2O3. The microstructure of the coating was characterized by scanning electron microscopy, which showed that the coating had a compact structure. The thermal conductivity of the coating was 23.7 W/m&middot, K, which is significantly higher than that of amorphous Al2O3 coating. The total and specific breakdown voltages of the coating were 3.85 kV and 26.92 kV/mm, which is suitable to apply for high power LED heat sink substrate.

Two kinds of metal oxide coatings were fabricated on 7050 Al alloy by hard anodization (HA) and micro-arc oxidation (MAO) techniques. The microstructure, phase composition, and corrosion behavior of the two coatings were studied by scanning electron microscopy, X-ray diffraction, and corrosion tests, respectively. When compared with the HA coating, the MAO one was more effective to isolate the substrate from the corrosive environment. In addition, as confirmed by electrochemical tests, the MAO coating was of better corrosion resistance than the HA coating. Furthermore, it was revealed by neutral salt spray test that the MAO coating could protect substrate alloy over 1140 h, while the HA coating can only protect substrate alloy for 46 h due to the amorphous composition and through thickness defects (micro-pores and micro-cracks)., The authors gratefully acknowledge the financial support of the project from the National Natural Science Foundation of China (Nos. 51571114, 51401106), the Natural Science Foundation of Jiangsu Province (No. BK20130935) and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).