Effects of the Alloying Elements on the Thermal Expansion Coefficients of Nonmagnetic N&base Alloys and Austenitic Steels

A regression model to predict the thermal expansion coefficient (averaged from room temperature to 538’C) of nonmagnetic nickel-base alloys and austenitic steels was obt,ained. The thermal expansion values used in the regression modelling were ta.kcn from published data bases of commercial alloys. An experimental verification of the model was also conducted on 23 nickel-base laborat,ory heats of varying chemical compositions: 19 solid solution alloys and 4 precipitation-hardened alloys. The experimental results confirmed the effects of the alloying elements as predicted by the regression model,: Mn, Fe and Cr increased the thermal expansion coefficient of alloys whereas MO, W, C, Al, Ti and (Nb+Ta) decreased it. The effects of MO, Al and Ti agreed with the results of prior experimental work on similar alloys. A preliminazy evaluation of the resistance to SCC (Stress Corrosion Cracking) of the experimental alloys showed that the solid solution alloys had a good resistance in boiling MgCl, solution and in pressurized, hot NaOH solution, whereas the precipitation-hardened alloys had a comparatively low SCC-resistance in the NaOH solution.