Influence of Alloying with Cobalt and Hafnium on the Corrosion and Hydrogen Resistances of Refractory Nickel Alloy

Abstract

We study the influence of alloying with cobalt (13.0 and 18.5 wt.%) and hafnium (0.3 and 0.7 wt.%) on the hydrogen embrittlement and salt corrosion of cast nickel alloy containing (wt.%) 0.08 C; 21.3 Cr; 2.4 Al; 2.8 Ti; 0.5 Nb; 0.015 B, and 0.005 Zr. At room temperature and under a hydrogen pressure of 35 MPa, we determined its characteristics of short-term strength and plasticity and the number of cycles to fracture. The resistance to high-temperature corrosion was estimated after holding in a 0.25 NaCl + 0.75 Na2SO4 salt mixture at 1073°K. It was discovered that hafnium additives significantly increase the corrosion and hydrogen resistance of the alloy. We also determined the optimal combination of strength, plasticity, low-cycle fatigue strength, and hydrogen and corrosion resistances for the alloy with 18.5% cobalt and 0.7% hafnium.