Enhancement of corrosion resistance of nickel based superalloys by laser surface melting

Abstract

Laser surface melting of Ni based superalloys (alloys 600, 690 and 693) was carried out to study the effect of surface modification on the corrosion behaviour in simulated nuclear high level waste (HLW) and chloride medium. Surface characterisation was performed by optical microscopy, scanning electron microscopy and X-ray diffraction. The alloys exhibited cubic crystal system and cellular microstructure. Double loop electrochemical potentiokinetic reactivation test in 0?5M H 2 SO 4 containing 0?0001M KSCN showed a low degree of sensitisation compared to the solution annealed specimens. Laser surface melting resulted in enhancement of corrosion resistance of the alloys in simulated HLW and chloride medium when compared to as received and solution annealed specimens; nevertheless, no discernable difference was found between the laser surface melted alloys 600, 690 and 693 in simulated HLW. However, the laser surface melted alloy 690 showed superior pitting corrosion resistance. The results of the present investigation are discussed in this paper.

Laser polishing of additively manufactured metal parts: a review

“…However, these AM technologies usually lead to a poor surface quality that does not meet the industrial requirements [66,67]. Currently, lots of methods exist to treat as well as improve the surface finishing of the AM as-built parts, and laser polishing is one of these [68]. Nevertheless, Inconel 718 is not easy to be processed by conventional machining processes mainly due to its low material removal rate and its high tool wear [69][70][71][72].…”

Laser surface melting of nickel-based alloy reduces nickel release in the primary cooling system of a nuclear power plant

“…High temperature oxidation is classically performed using conventional heat treatments but laser processing of materials has extended the possibilities and is being increasingly used to optimize surface properties [25]. Among numerous techniques, laser surface melting (LSM) offers a significant potential for improvement of the corrosion behaviour [26][27][28][29][30][31][32][33]. For another application in the nuclear fuel cycle (storage of high level waste) LSM treatment of alloy 690 leads to an improved resistance to pitting corrosion due to chloride ions [27].…”

“…Among numerous techniques, laser surface melting (LSM) offers a significant potential for improvement of the corrosion behaviour [26][27][28][29][30][31][32][33]. For another application in the nuclear fuel cycle (storage of high level waste) LSM treatment of alloy 690 leads to an improved resistance to pitting corrosion due to chloride ions [27]. It has also been observed on chromium containing alloys that LSM can enrich the surface in chromium [28,34].…”

Electrochemical polarisation studies on plasma-sprayed nickel-based superalloy

“…The bare metals are inclined to the highly aggressive corrosive medium, and it requires surface modification or coatings to enhance the surface properties. Researchers employ various thermal barrier coatings (TBCs) involving different coating processes, namely vacuum plasma spraying (VPS), low-pressure plasma spraying (LPPS), atmospheric plasma spraying (APS), high-frequency pulse detonation and high-velocity oxygen fuel spraying (HVOF) [3][4][5][6][7]. The plasma spray technique was found to be one of the best and versatile coating processes for thermal barrier coating materials [8].…”