Laser surface modification using Inconel 617 machining swarf as coating material

A single-stage, blown powder laser cladding process is used to deposit a protective layer of Ni-based alloy Inconel 617 on mild steel substrates. A Design of Experiments methodology is used to analyse the effects of the major laser cladding processing parameters on the deposited layer characteristics. Layer thickness, microstructure, dilution, elemental composition and corrosion resistance are analysed and correlated with the processing parameters and the overall effectiveness of the protective coating assessed. The work is different in that the protective material, usually in the form of costly powder, is in this case virtually cost-free and simply recycled from machining waste without any costly atomisation or similar process. The results show a number of significant relationships between the processing parameters and the effectiveness of the protective coating. The layer thickness and hardness were found to increase with the mass feed rate and decrease with an increase in laser power. A mainly columnar dendritic microstructure was observed in the clads. There was no evidence of significant bonding defects, trapped unmelted particles or porosity under most conditions. In all samples, the coatings displayed significant higher corrosion resistance than the mild steel sample.