Volume and Grain-Boundary Diffusion in 20 Cr/25 Ni/Nb Stainless Steel

Abstract

Standard radiotracer techniques have been used to measure the volume-diffusion rates of chromium and nickel in a 20 Cr/25 Ni/Nb austenitic steel in the temperature range 840–1290° C. Within the limits of experimental uncertainty, the results are described by D _Cr = 0·19 exp (−58·8 × 10³/RT), D _Ni = 4·06 exp (−67·5 × 10³/RT). Grain-boundary-diffusion measurements have been made in the range 550–900° C. The diffusion rates of chromium and nickel isotopes are not significantly different from previously reported values for iron. Combining the data for all three elements gives a mean Arrhenius equation δD_B = 1·5 × 10⁻⁷ exp (−44 × 10³/RT).