Hot corrosion and internal spallation of laser-cladded inconel 625 superalloy coatings in molten sulfate salts. (December 2021)

• Record Type: Journal Article
• Authors: Liu, Hongfei; Tan, Chee Kiang Ivan; Meng, Tzee Luai; Teo, Siew Lang; Liu, Junyi; Cao, Jing; Wei, Yuefan; Tan, Dennis C.C.; Lee, Coryl J.J.; Suwardi, Ady; Lin, Ming
• Is Part Of: Corrosion science. Volume 193(2021)
• Publication Date: 2021-12
• Subjects: Hot corrosion -- Molten sulfate salts -- Inconel 625 -- Laser-cladding -- Diffusion zone; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2021.109869
• Languages: English
• ISSNs: 0010-938X

Abstract

Abstract: Hot corrosions of laser-cladded inconel 625 in molten salt of Na2 SO4 -MgSO4 mixture have been studied at 900 °C to address its anticorrosion behaviors. Elemental and microstructural characterizations provide direct evidence for the formation of MgO/Cr2 O3 external layers and the outward-diffusion of Cr atoms. The Cr-depletion promotes precipitation of δ-Ni3 (Nb/Mo), nucleation and accumulation of dislocations, pores, and internal spallation of the corroded alloy. They also provide evidence for the diffusion of sulfur into the near-surface region, leading to the formation of internal sulfide scales (i.e., Nb4−x Crx S6, CrS, and MnCr2 S4 ). Grain boundaries play important roles in the atomic diffusions and sulfide formations. Graphical Abstract: ga1 Highlights: Hot corrosions of laser-cladded inconel 625 in molten salt mixture of Na2 SO4 -MgSO4 . External dual-layer MgO/Cr2 O3 formed with Cr2 O3 immediate on inconel 625. Cr outward-diffused and S inward-diffused, dominantly along the grain boundaries. Cr depletion promoted δ-precipitations, dislocations, pores and internal spallation. S-diffusion led to internal sulfide scales without internal oxide scales at all.