Causes and Classification of Cracks in Laser Cladding

The causes of cracks
During the fusion process, the high-energy laser beam rapidly heats up, causing a significant temperature gradient between the fusion layer and the substrate. In the subsequent cooling, the volume of the cladding layer and the substrate is inconsistent, which constrains each other and generates stress.

During the growth process of the eutectic structure in the laser cladding layer and the coarse dendrites at the bottom of the cladding layer, the presence of dendrite segregation causes intergranular weakening, and cracks often propagate along their grain boundaries.

Classification of laser cladding cracks
1. Cracks in the cladding layer
Generation method: generated during the solidification process of molten metal.
Production area: Formed on the surface or inside of the cladding layer and extending towards the substrate direction.

2. Interface cracks
Generation method: Microcracks caused by defects such as pores and inclusions.
Production area: It occurs at the interface between the cladding layer and the substrate, and extends towards the surface layer.

3. Scanning for cracks in overlapping areas
Generation method: It is formed when the molten metal cannot be fully wetted.
Production area: at the junction of the lap joint and the substrate.