激光合成TiC/Ni涂层裂纹控制技术

Cracking control technology of TiC/Ni coatings prepared by in-situ fabrication through laser cladding

关键词:  激光熔覆  原位合成  裂纹控制  置换反应

Key words:  in-situ fabrication  laser cladding  cracking control  replacement reaction

摘要:

激光熔覆原位合成TiC/Ni涂层开裂严重.从熔覆层金相组织、物相组成、残余应力、宏观形貌和断口观察等角度分析裂纹形成的原因,提出了相应的裂纹控制措施.结果表明,激光合成TiC/Ni涂层裂纹主要是由于硬脆相及残余内应力导致的脆性冷裂纹.通过增大钛粉量,Ti元素与Ni60中的M₂₃C₆相发生置换反应:M₂₃C₆+Ti→M+TiC.通过加入镍粉或优化工艺参数,可以改善涂层组织,提高塑韧性,降低残余内应力,从而降低裂纹敏感性。

Abstract:

There are many cracks in TiC/Ni coatings prepared by in-situ fabrication through laser cladding.The reasons for crack initiation in the coatings were analyzed from the microstructure, the phase composition, the residual stress, the macro morphology and the fracture observation.Corresponding cracking control measures were also proposed.The investigation indicated that the cracks of the TiC/Ni coatings are mainly brittle cold cracks caused by hard brittle phases and internal residual stress.The replacement reaction(M₂₃C₆+Ti→M+TiC) occurs by increasing the content of Ti powder.Therefore, cracks of the coatings can be reduced or eliminated.Moreover, intriguing microstructures of the coatings are obtained with enhanced plasticity and toughness and reduced residual stress by nickel powder addtion or by optimizing processing parameters, thus the cracking susceptibility can be decreased.