激光熔覆Ni 基金属陶瓷复合涂层的裂纹研究

利用激光熔覆技术在中碳钢表面制备了不同涂层成分的原位自生TiB₂ / Ni 金属陶瓷复合涂层, 研究了涂层的开裂行为。结果表明: 当陶瓷相含量高时, 涂层中形成的裂纹主要有粘接金属基体中的穿晶裂纹、熔覆层边缘的高密度裂纹、金属基体与硬质陶瓷相界面上的微裂纹以及热影响区中结合界面附近的微裂纹等。涂层中的裂纹主要是由涂层材料与金属基体热膨胀系数不同而造成的热应力产生的, 组织转变应力也起了重要作用。当激光工艺参数及涂层成分配制合理时, 涂层质量良好。 

RESEARCHON THE CRACKS OF Ni-BASED METAL-CERAMICCOMPOSITE COATING BY LASER CLADDING

In-situ synthesized TiB2 / Ni metal-ceramic composite coatings with different compositions were fabricated on the medium carbon steel using laser cladding. The cracking behavior in different coatings was studied bymicroanalysis. The result s show that the cracks formed in the coating with high content of ceramic phases are mainlythe following : the t ranscrystalline cracks in the bonding metal mat rix, the high density cracks at the edge of thecoating, micro-cracks on the interface of the mat rix and the hard ceramic phases and in the vicinity of the bondinginterface in the heat-affected zone, etc. The cracks in the coating are mainly caused by the thermal st ress induced bythe difference of the thermal expansion coefficient s of the coating materials and the metal mat rix, and the t ransformation st ress plays an important role too. The good quality coating can be obtained by optimal laser parametersand coating compositions.