Friction surfacing of AISI 904L super austenitic stainless steel coatings: Microstructure and properties

Microstructure, texture, pitting corrosion resistance and hardness of surfaces and cross-sections of the friction-surfaced (FSed) super austenitic stainless steel 904L coatings fabricated at various spindle speeds were investigated. The microstructure of the coatings was governed by both dynamic recovery (DRV) and continuous dynamic recrystallization (cDRX) owing to the high stacking fault energy (SFE) of 904L. The grain orientations in DRV were in A₂^⁎ shear texture component, while the rotated cube textures were related to the cDRXed grains. Immersion tests of the FSed coatings in 3.07 mol/L Cl⁻ solution showed that the corrosion pits were slightly preferred to generate at the {111} DRVed grains on the coating surfaces, since these grains were likely to have a higher elastic strain during FS. Compared with AISI 304, the pitting potential of the FSed coatings in 3.5 wt% NaCl solution was significantly shifted to nobler direction and also insensitive to spindle speed owing to the high SFE of 904L. However, the passive films of the FSed coatings were thinner and more difficult to reform, as evidenced by slightly larger average pit diameters and lower protection potentials owing to the high residual stress caused by FS.