Al_2O_3-TiO_2对铝合金表面激光熔覆NiAl涂层组织性能的影响

Effect of Al_2O_3-TiO_2 on Microstructure and Properties of NiAl Coating by Laser Cladding on Aluminum Alloy

目的进一步提高6061铝合金表面的硬度、耐磨性。方法应用脉冲Nd:YAG激光器在6061铝合金表面制备了NiAl合金涂层和NiAl/Al_2O_3-TiO_2复合涂层。通过SEM、X射线衍射仪系统研究了Al_2O_3-TiO_2陶瓷相添加对NiAl熔覆层组织形貌、成分分布、物相组成的影响。利用HVS-1000硬度测试仪及HSR-2M高速摩擦磨损机,对熔覆层硬度分布及耐磨性进行测试分析。结果Al_2O_3-TiO_2陶瓷颗粒加入使涂层宏观成形质量明显提高,表面平整光滑、波纹均匀,熔覆层枝晶间距减小,组织结构明显细化。与NiAl熔覆层相比,在NiAl/Al_2O_3-TiO_2复合涂层中,具有较高硬度的Al_3Ni、Al_3Ni_2硬质相含量增大。同时,高硬度Al_2O_3和良好韧性的Ti O_2、NiTi金属间化合物在复合涂层内部形成。NiAl/Al_2O_3-TiO_2复合涂层的显微硬度平均可达650HV_(0.2),相比NiAl涂层提高了300HV_(0.2);磨损体积仅为铝合金基体的1/9,相比NiAl涂层降低了35%。干摩擦条件下,NiAl/Al_2O_3-Ti O_2复合涂层的犁削、剥落现象显著降低。结论在细晶强化、硬质相弥散强化及良好韧性的NiTi金属间化合物共同作用下,6061铝合金表面硬度和耐磨性得到显著提高。

The work aims to improve the abrasion resistance on 6061 aluminum alloy further.NiAl and NiAl/Al2O3-TiO2 composite coatings were prepared on the surface of 6061 aluminum alloy by pulse Nd:YAG laser.SEM and X-ray diffraction were used to investigate the effects of Al2O3-TiO2 ceramic phase on microstructure,element distribution and phase composition of NiAl coating.The hardness distribution and wear resistance of the coating were analyzed by HVS-1000 hardness tester and HSR-2M high-speed friction tester,respectively.Al2O3-TiO2 ceramic particles added to the cladding coating improved the quality of macromorphology and led to a smooth and uniform surface.The dendrite spacing decreased and the microstructure refined obviously.Compared with NiAl cladding coating,the amount of Al3Ni and Al3Ni2 with higher hardness in NiAl/Al2O3-TiO2 composite coating increased.Meanwhile,the Al2O3 reinforced phase and TiO2 and NiTi with better toughness were formed in the composite coating.The average microhardness of NiAl/Al2O3-TiO2 composite coating was about 650HV0.2,which was 300HV0.2 higher than that of NiAl coating and the wear volume was only 1/9 to matrix,which was 35%lower than that of NiAl coating.Under the condition of dry friction,the plowing and peeling of NiAl/Al2O3-TiO2 composite coating decreased significantly.With the combination effect of the grain refinements,dispersion strengthening and better toughness of the NiTi intermetallic compounds,the microhardness and abrasion resistance of 6061 aluminum alloy significantly improve.