A comparison of the corrosion behavior of WC-Co-Cr and WC-Co HVOF thermally sprayed coatings by in situ atomic force microscopy (AFM)

The corrosion behavior of WC-Co-Cr and WC-Co high velocity oxygen fuel (HVOF) sprayed coatings were examined in static saline conditions. Direct current (DC) polarization tests were conducted and the electrochemical corrosion behavior was shown, by in situ atomic force microscopy (AFM) and scanning electron microscopy (SEM), to be complex because of the composite ceramic-metal nature of the coating. The addition of chromium to the matrix greatly enhanced the corrosion resistance of the coating.     

Atomic force microscope study of the interface of twinned martensite in copper–aluminium–nickel

Atomic force microscopic observations of interfacial structures of twinned γ₁^′ martensite plates in single crystals of Cu–14wt.%Al–3.4wt.%Ni alloy revealed the presence of either side-plate extensions or well-defined twin facets at the martensite/parent phase interface. These results indicate that there are alternative means of accommodating micro-scale mismatch strains at the interface.     

A scanning force microscopy study of grain boundary energy in copper subjected to equal channel angular pressing

We employed a scanning force microscopy technique to determine the ratio of grain boundary and surface energies in copper using the thermal grooving method. Samples of ultrafine grain copper obtained by four passes of equal channel angular pressing were heat treated in a reducing atmosphere at 400 °C for 15 min and at 800 °C for 2 h. The average dihedral angles of the grain boundary grooves after the former and the latter heat treatments were 152.4 ± 6.3° and 164.2 ± 4.3°, respectively, which can be translated into the difference by a factor of 1.8 in average grain boundary energies. This difference implies that the grain boundaries in ultrafine grain copper produced by equal channel angular pressing are in a state of high non-equilibrium that cannot be fully relaxed after a short annealing at 400 °C, but that undergoes significant relaxation after annealing at 800 °C.     

紫外/臭氧辅助不锈钢表面聚二甲基硅氧烷自组装膜的形成及其性能研究

目的 在不破坏不锈钢表面的前提下,使用自组装技术提升不锈钢表面的耐腐蚀性能和抗磨损性能。方法 首先采用紫外/臭氧(UV/O3)辅助处理的方法活化316L不锈钢表面,然后利用浸泡法在其表面制备聚二甲基硅氧烷(PDMS)自组装膜。通过原子力显微镜(AFM)、接触角测量仪、电化学工作站、摩擦磨损试验机等设备分析了UV/O3处理时间对316L不锈钢表面的影响以及自组装时间对316L不锈钢表面耐腐蚀、抗磨损性能的影响。结果 UV/O3处理时间为20 min时,316L不锈钢表面具有良好的亲水性,且此时粗糙度最低。316L不锈钢表面在形成PDMS自组装膜之后缓蚀效率大幅度提升,且缓蚀效率在自组装时间为0.5 h时最佳,达到90.51%。同时,在经过20 min UV/O3辅助处理后的不锈钢上制备的自组装膜相较于未经UV/O3辅助处理得到的自组装膜,覆盖率更大,缓蚀效率更高。进一步的摩擦磨损试验结果表明,经过UV/O3辅助处理后形成PDMS自组装膜的316L不锈钢表面,摩擦因数从0.85降低到0.25。相较于直接自组装的不锈钢表面在140 s后发生磨损,经过UV/O3预处理后再自组装的不锈钢表面在530 s后才发生磨损。结论 UV/O3辅助处理能够在不损伤不锈钢表面的前提下,通过活化不锈钢表面以提高其膜基结合强度,从而提升不锈钢表面自组装成膜的效果。316L不锈钢表面经过UV/O3预处理20 min后在25 ℃下自组装0.5 h,可以成功得到耐腐蚀性能和抗磨损性能良好的PDMS自组装膜,这一方法有效降低了不锈钢在高浓度氯离子环境中的失效风险,同时也提高了不锈钢表面的耐磨性能。