H-induced C–Cr cluster redistribution in MANET steel

Abstract Internal friction (IF) and dynamic modulus (M d ) measurements have been performed on samples of MANET steel (10.5% Cr, 0.17% C) to study the interaction of H with C–Cr n clusters. Samples of MANET steel as-quenched and annealed for 7.2×10 4 s at 973 K have been permeated by flowing H at 873 K. The IF curves have been analysed using the linear approach proposed by Sarrak, Tomilin, Golovin and Suvorova and fitted as the sum of seven Snoek-type peaks corresponding to a different number n of Cr atoms (0≤ n ≤6) at the corners of the octahedron around the C atom. The comparison between Q −1 spectra of samples before and after H permeation shows that a redistribution of C–Cr n clusters takes place. In particular, H appears to preferentially interact with C of the C–Cr n clusters with a higher number of Cr atoms.