Abstract
Ni–xCr–Mo laser-cladding coatings with varying Cr content of 10, 15, 20, 25, and 30 wt.% were fabricated using a self-assembled coaxial laser-cladding device. The H2S-induced high-temperature corrosion tests under reductive atmosphere were conducted at 500, 550, and 600 °C. Subsequently, the influence of Cr content on the microstructural evolution and corrosion resistance of the Ni–xCr–Mo coatings was investigated. The experimental results revealed that 30 wt.% Cr is the limited maximum content that forms the suitable morphology of coatings without large prominent pores and cracks during the fabrication process, and 15 wt.% Cr corresponds to the critical minimum content for excellent corrosion resistance, as implied from the variation tendency of the corrosion weight-gain curves. Moreover, a two-layer structure of the corrosion scales was observed in the Ni–xCr–Mo laser-cladding coatings, which was primarily caused by the selective corrosion between the Ni and S and Cr/Mo and O.
Highlights
Ni–Cr–Mo alloys such as Hastelloy C22, Hastelloy C276, C-4, and Inconel 625 have garnered considerable attention owing to their high corrosion resistance against pitting, crevice, and stress corrosion [1–7]
The corrosion resistance of Ni–xCr–Mo laser-cladding coatings increased with the Cr content
The sulfur corrosion tests of Ni–xCr–Mo laser-cladding coatings were conducted in an H2 S reducing atmosphere at 500–600 ◦ C within the simulated atmosphere furnace
Summary
Ni–Cr–Mo alloys such as Hastelloy C22, Hastelloy C276, C-4, and Inconel 625 have garnered considerable attention owing to their high corrosion resistance against pitting, crevice, and stress corrosion [1–7]. Ni–Cr–Mo alloys are widely used across the modern industry because of their excellent corrosion resistance toward chlorine, hot pollution solution, strong acid, strong alkali, organic solvents, and high-temperature corrosion, establishing their ability of exceptional corrosion resistance [8–11]. Liu et al [1] reported that the corrosion resistance ability of Hastelloy C22 prepared using a pulsed optical-pumped Nd:YAG laser was equal to that of the bulk one. The laser-cladding technology was used to prepare the Ni–Cr–Mo cladding coating owing to its high power, strong metallurgical bonding with matrix, small heat-affected zone, and small matrix deformation [13,14,20,21].
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