Abstract
The L-605 alloy is cobalt-base heat-resisting alloy used as structural material with high temperature oxidation resistance. L-605 alloy has been used as a constituent material of a fluid catalytic thruster for the attitude control system of the satellites because of its high corrosion resistance and high strength. However, it has been already reported that hydrogen, nitrogen and ammonia deteriorate the L-605 alloy with plastic deformation in high-temperature environment. Therefore, in order to investigate the deterioration mechanism of the alloy, heat treatment was carried out with introduction of strain for L605 alloy. Heat treatment for L-605 alloy was conducted in ammonia gas atmosphere. The microstructure observation and tensile test for L-605 alloy were conducted. Tensile strength and 0.2% proof stress increases and elongation and reduction of area decrease with increasing rolling reduction. The chromium nitrides were separated out in the alloy after the heat treatment. These results indicate that brittle fracture of L-605 alloy is possibly promoted by heat treatment in ammonia gas atmosphere and the introduction of strain.
