The influence of stellite 6 particle size on the inter-track porosity in multi-track cladding

The formation of multi-track laser cladding of stellite 6 with different particle size on mild steel was carried out with different geometry profiles and levels of dilution in the single-track clad in order to examine the influence of particle size on clad geometry and inter-track porosity. The clad area and total area including clad area, the remelted area of previous track and substrate melted area in each track were measured. Both clad area and total area increase with track number and finally reach steady values, but the increase in total area is much greater than that in clad area. The remelted area of previous track increases with the level of dilution of the single-track clad and reaches the maximum value when the dilution of single-track clad is over 20%. The percentage of the maximum remelted area of the previous track equals the percentage of the track overlap. The steady values of these areas are given by empirical analysis. The inter-track porosity will appear when the difference between the total area and the remelted area of the previous track is closer to or smaller than the clad area because there is insufficient laser energy to melt the powder captured by the melt pool. The tendency for inter-track porosity formation is higher in laser cladding with finer powder due to its smaller total area. A new criteria based on the single-track clad geometry for specific stellite powder is proposed to determine the appearance of inter-track porosity.