Effects of oxide on fatigue crack growth behaviour of type 347 stainless steel in PWR water conditions

Abstract

The fatigue crack growth behaviour of type 347 stainless steel in pressurized water reactor (PWR) conditions was investigated at two different temperatures, 25 and 316 °C. The fatigue crack growth rate was slightly increased at the elevated temperature in air. In the simulated PWR water environment, the fatigue crack growth rate was changed in a rather complicated manner with a change of the dissolved oxygen (DO) content. The DO content did not significantly change the fatigue crack growth rate at 25 °C. With the lower oxygen content of 5 ppb, which is the practical limit of deoxygenated water, the fatigue crack growth rate was similar at both 25 and 316 °C. The fatigue crack growth rate was significantly decreased at 316 °C with the higher oxygen level of 100 ppb. Under 316 °C water conditions, oxides were observed on the fatigue crack surface where the size of oxide particles was about 0.2 µm at 5 ppb and about 1 µm at 100 ppb. The thickness of the oxide layers also increased with the increase of DO. Moreover, the ΔK threshold (ΔKth) also increased as the DO increased from 5 to 100 ppb. The dissolved hydrogen levels did not affect the measured crack growth rate at the given test conditions. The decrease of the fatigue crack growth rate with higher DO content is attributed to a crack closure resulting from the formation of larger oxides near the crack tip at a rather fast loading frequency of 10 Hz that was used in this study.

On the fatigue behaviour of quenched and tempered at 300 and 600 °C SAE 1045 steel in an environment of sugar cane juice

“…In engineering, it is well known that the environment and temperature have important effect on fatigue strength as shown in recent studies. [9][10][11][12][13][14][15][16][17][18] The combined effect of fatigue and corrosion threatens the integrity of the materials; this combined effect is more aggressive than the sum of the two effects individually. 15,18,19 In addition to the corrosion fatigue effect, there is shaft journal deterioration produced by a combination of two different wear phenomena: abrasion and adhesion.…”