CRACKING BEHAVIOR OF CERAMIC PARTICLES REINFORCED NI-BASE ALLOYS COMPOSITE COATING BY LASER CLADDING

In-situ synthesized TiB2 particles reinforced Ni-base composite coatings with different compositions were fabricated on medium carbon steel using laser cladding. Cracking behavior in different coatings was studied by microanalysis. Results show that the coating quality is good with optimal laser parameters and coating compositions; whereas the cracks formed in the coating with high content of ceramic phases mainly include the following: the transcrystalline cracks in the bonding metal matrix, the high density cracks in the edge of the coating, micro-cracks on the interface of the matrix and the hardy ceramic phases and in the vicinity of the bonding interface in the heat-affected zone etc. Cracking behavior in the coating is mainly attributed to the thermal stress induced by the difference of the thermal expansion coefficient of the coating materials and the metal matrix, and the phase transformation stress plays an important role too.