纳米复合材料激光熔覆层组织及抗磨性能

利用5kWCO2激光器，在Ni基高温合金表面制备了纳米Al2O3／钴基合金熔覆层，分析了熔覆层的组织结构及其抗磨性能．结果表明，当纳米Al2O3颗粒含量较低时，Al2O3颗粒能均匀分布于熔覆层中，从而形成纳米氧化物弥散强化的复合材料涂层；Al2O3颗粒在熔池中长大，尺寸为250-450nm；复合材料熔覆层的硬度随纳米Al2O3含量的增加而提高；当纳米Al2O3颗粒含适中时，熔覆层的抗磨性能较好；而当纳米Al2O3颗粒含量过高(3．0％)时，复合材料熔覆层的抗磨性能反而降低。

Microstructure and Wear-Resistance of Nano-Al2O3 Doped Co-Alloy-Based Composite Coating Produced by Laser Cladding

Cobalt-based composite coatings doped with nano-Al_2O_3 were prepared on Ni-based superalloy substrate by laser-cladding of a CO_2 laser. The microstructures of the coatings were analyzed by means of optical microscopy, scanning electron microscopy, and transmission electron microscopy, while the elemental composition and phase composition of the composite coating were determined by means of X-ray diffraction and energy dispersive X-ray analysis. Moreover, the microhardness of the coatings were measured, while the friction and wear behaviors of the composite coatings sliding against 9CrSi alloy in a block-on-ring configuration were evaluated on an MM-200 test rig. The worn surface morphologies of the composite coatings were also observed by means of scanning electron microscopy. It was found that the incorporation of the nano- Al_2O_3 particulates contributed to increasing the microhardness and wear-resistance of the laser-cladded composite coating, which was attributed to the dispersive strengthening effect and fine-crystalline strengthening effect of the nano-particulates. However, with the increase of the nano-Al_2O_3 amount in the composite coating, the nano-particulates would agglomerate and act as entrapped impurities of decreased bonding strength with the Co-alloy matrix, which led to the decrease in the wear-resistance of the coating. The composite coatings were characterized by scuffing, adhesion, and spalling as they slid against the 9CrSi alloy. Specifically, the enhanced adhesion and spalling of the composite coating with a higher content of nano-Al_2O_3 corresponded to its poorer wear-resistance, though it had a relatively larger microhardness.