Product Code: ICAL07_109

Comparison of Microstructures and Properties of Laser Surface-Treated Thermally Sprayed and Laser-Clad Coatings of Inconel 625
Authors:
Guijun Bi, University of Nottingham; Nottingham Great Britain
K.T. Voisey, University of Nottingham; Nottingham Great Britain
Nauman Ahmed, University of Nottingham; Nottingham Great Britain
D.G. McCartney, University of Nottingham; Nottingham Great Britain
I.R. Pashby, University of Nottingham; Nottingham Great Britain
Presented at ICALEO 2007

Inconel 625 is a corrosion-resistant Ni-based alloy which has multiple applications in various industrial sectors including aerospace and petrochemical. Whilst thermal spraying is frequently used to form Inconel 625 coatings, the resultant coating contains some process-inherent features such as oxides thus making it less effective. A post-spray laser remelting treatment is helpful in eliminating oxidised regions and restoring corrosion performance. However, this 2-step approach is cumbersome in terms of cost and time. Alternatively, a one-step laser cladding technique can be used. The process of laser cladding can be further enhanced to repair or laser rapid manufacturing (LRM) by layer-by-layer deposition of material. In this paper, a high power diode laser is used to clad a surface layer of Inconel 625 (in powder form) on mild steel. Following laser surface cladding (1-step approach), the microstructure and properties (electrochemical and mechanical) are evaluated and compared with laser surface treated sprayed coatings (2-step approach). The materials are characterised using optical and scanning electron microscopy and X-ray diffraction. The results indicate that both processes have the potential to form pore and crack-free coatings. Moreover, laser-treated and laser-clad deposits have dendritic microstructures with properties distinctly different from the wrought alloy or the as-sprayed coatings.