Preparation of Thick Ceramic Coating by Laser Multi-Layer Cladding I - Crack Control

The formation of cracks is one of the key problems which restricts the development and application of laser-clad ceramic coating technique on metal surface, especially during laser multi-layer cladding process because of stress superposition effect. In this study, a thick ceramic coating was fabricated by laser multi-layer cladding based on series of crack control methods. The crack of clad layer was controlled by preheating and slow cooling rate of sample with incubator, applying the ultrasonic vibration and adopting closed-loop controlling temperature of molten pool during laser cladding process. In addition, the crack of layer was controlled by the strengthening and toughening effect of remained nanoparticles in the laser-clad coating. Moreover, the use of a transition layer is also help to reduce layer cracks. The results show that the laser-clad ceramic coating is free of macroscopic cracks and the mcirocrack density is significantly reduced.