Metallurgical and geometrical characterisation of the 316L stainless steel clad deposited on a mild steel substrate

- Variations in clad dimensions have been correlated with process parameters.
- Effect on dilution, HAZ, clad dimensions, and specific energy is reported.
- The term “End-of-track cracking” has been coined in this manuscript.
- Possible mechanisms of crack formation during process termination are presented.

In this study, the characteristics of the clad of 316L stainless steel deposited onto the mild steel substrate was investigated, in terms of dimensional and metallurgical variation across the length of the tracks. Significant variation in the clad thickness, depth of penetration of the melt pool, and depth of the heat affected zone (HAZ) was observed and correlated with the process parameters including laser power, scan speed, dilution, and specific energy of the laser beam. A significant variation in the clad thickness was observed across the entire length of the tracks. Based on this observation, three zones were identified and their characteristics discussed. Microstructural variation in the clad as well as the HAZ has been presented in detail. Moreover, hardness values ranging between 400-450 HV and 320-380 HV was measured in the deposited tracks with clad thicknesses of 0.5 and 1 mm, respectively. This was attributed to the presence of fine austenitic grains of the size 4-8 μm. Apart from the minute porosities observed in the clads, micro-cracking on the top surface of the tracks due to residual thermal stresses has also been reported. Lastly, “end-of-track” cracking was noticed in the deposited tracks and the possible mechanisms of crack formation are discussed.