Effect of Boron Addition on Fatigue Crack Growth Characteristics of Austenitic Stainless Steel

Abstract

Borated austenitic stainless steel, B-SUS304P-1, has been used for storage and transportation cask in the nuclear industry, because it has enough structural strength, heat dissipation function and neutron absorption ability. In the present study, fatigue crack growth (FCG) tests were conducted under stress ratio, R, and maximum stress intensity factor, K_max, constant conditions and the FCG rates of B-SUS304P-1 were compared with those of SUS316. In order to clarify the upper bound characteristics of FCG, fracture toughness tests were performed for both materials according to the ASTM standard E1820 and revealed the crack growth characteristics under static loading condition. Detailed observations of fracture surfaces indicated that the boride consisted of iron, chromium and boron and produced locally flat fracture surface, which suggested brittle fracture. However, the FCG rates were insensitive to the boride presence, while the fracture toughness was reduced. Based on the results, the effect of boron addition on the FCG characteristics were discussed over the wide range of FCG rate.