Evaluation of hot corrosion performance of 904L stainless steel through corrosion-enhanced erosion testing at elevated temperature (650 °C)

Abstract

The hot corrosion-enhanced solid particle erosion behavior of super austenitic stainless steel 904L was investigated at 650 °C. Cyclic corrosion tests (25 hours in 5-hour cycles) employed a Na 2 SO 4 –NaCl (3:1 wt%) salt deposit of 4.0–4.5 mg cm −2 . Salt-coated specimens obeyed a parabolic rate law (k p  = 10.71 mg 2 cm −4 h −1 ), multifold faster than the linear oxidation rate (k l  = 0.0313 mg cm −2 h −1 ), confirming eutectic-assisted fluxing above 617 °C. X-ray diffraction identified Fe 2 O 3 , Fe 3 O 4 , Cr 2 O 3 , FeCr 2 O 4 , Na 2 CrO 4 , NiO, NiCl 2 , and CrCl 3 as the primary corrosion products, forming a structurally heterogeneous, weakly adherent multi-phase scale. Erosion testing (ASTM G76-95; Al 2 O 3 , 50 µm, 100 m/second; flux rates 2.7 and 4.0 g/minute; angles 30°, 60°, and 90°) showed that hot-corroded surfaces eroded at substantially higher rates than oxidized surfaces across all conditions, with synergistic loss exceeding the sum of individual contributions. Micro-cutting and ploughing dominated at 30°, while particle embedding and plastic deformation prevailed at 90°. Increasing flux from 2.7 to 4.0 g/minute elevated erosion rates sub-linearly, consistent with inter-particle shielding. The corrosion–erosion interaction is driven by interface-mediated delamination of the multi-phase scale and Cl − -assisted grain-boundary attack, mechanisms with direct implications for lifetime prediction in boilers, fluidized-bed combustors, and high-temperature chemical processing equipment.