Elimination of Start/Stop defects in laser cladding

Laser cladding represents an advanced hard facing technology for the deposition of hard, corrosion and wear resistant layers of controlled thickness onto a selected area of metallic substrate. When a circular geometry is required, the beginning and the end of the laser track coincide in the same area. When no special attention is paid the formation of irregular microstructural features results in non-homogeneous properties and even to cracking. This paper reports a few specially designed strategies that are tested to solve this problem. Laser cladding experiments were performed using 3.3 kW IPG Fiber laser, SS304 steel substrate bar 40 mm in diameter and two coating powders: Iron and Cobalt based. Standard metallographic methods, Scanning Electron Microscopy equipped with Energy Dispersive Spectroscopy and microhardness measurements were used to study the microstructure and properties inside the laser track overlapping areas created by different cladding strategies. These strategies were ranked according to a particular set of criteria. Correlations between the hardness variations and ‘local dilution’ inside the Start/Stop zone were identified for both materials.