Laser cladding of Inconel 625 wire for corrosion protection

• Published in: Journal of materials processing technology Vol. 217; pp. 232 - 240
• Main Authors: Abioye, T.E., McCartney, D.G., Clare, A.T.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-03-2015
• Subjects: Austenitic stainless steels; Beads; Cladding; Coating; Corrosion; Dilution; Inconel 625; Laser cladding; Micro-hardness; Microstructure; Nickel base alloys; Pitting (corrosion); Superalloys; Wire; Dilution; Inconel 625; Micro-hardness; Corrosion; Laser cladding; Microstructure
• ISSN: 0924-0136
• DOI: 10.1016/j.jmatprotec.2014.10.024

•A strategy for high integrity laser cladding of stainless steel components with the corrosion resistant Inconel 625 wire is presented.•The mechanism of enhanced corrosion as a result of Fe dilution is reported.•Corrosion performance of the typical Inconel 625 wire laser coating is shown to be very similar to the wrought Inconel 625.•The corrosion performance of the coatings degrades with increasing Fe dilution.•Corrosion resistance of Inconel 625 wire laser coating is superior to the wrought 304 stainless steel.
The electrochemical corrosion performance of laser clad Inconel 625 wire in a de-aerated 3.5 wt% NaCl solution was investigated. The microstructure of the clad beads before and after the corrosion testing was examined using a combination of optical microscopy, scanning electron microscopy (with energy dispersive X-ray analysis) and X-ray diffraction. Well bonded, minimally diluted, pore- and crack-free single bead and multiple (overlapped) beads of Inconel 625 wire were successfully deposited. The clad beads comprise dendritic γ-Ni (FCC) matrix and interdendritic precipitates which are Mo- and Nb-rich. The microstructural evolution of a typical clad bead is observed to begin with columnar dendrites, at the clad-substrate interface, growing vertically to the substrate. This blends into horizontal columnar dendrites near the top region. High integrity laser coating (multiple beads) of Inconel 625 wire with a minimal dilution ratio of 4.5% is found in this study. The corrosion performance of the coating, which degrades with increasing Fe dilution, is very close to that of wrought Inconel 625 but superior to the wrought 304L stainless steel. The stainless steel exhibited localised (pitting) corrosion however, it was fully protected by the Inconel 625 wire laser coating in the saline solution.