High-throughput Characterization of Threshold Stress for Stress Corrosion Cracking

Kewei Gao*, Qian Yan, Luchun Yan, Xiaolu Pang, Lijie Qiao

School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083

ABSTRACT: Due to the harsh service environment of subsea platforms, oil and gas pipelines, nuclear power installations and underground facilities, the steel structures are prone to stress corrosion cracking, which will have a catastrophic impact on the safe operation of facilities. Therefore, under the designed load-bearing conditions and service environment, it is very important to predict whether and when the crack will initiate. The traditional method is to obtain the fracture time of standard parallel specimens under different applied constant load conditions, so as to determine the threshold stress of  stress corrosion cracking within a certain period of time. It takes at least 6-10 identical specimens to obtain a threshold stress for failure, which will cost a lot of time.

In order to solve this problem, this study proposes a high-throughput method for predicting the threshold stress of stress corrosion cracking based on the concept of materials genome initiative (MGI). The small tapered specimens of 316L stainless steel combined with the finite element simulation was used to predict the threshold stress of stress corrosion cracking under dynamic hydrogen charging and tensile state. The research results show that the length of the cracks without interaction between each other was used to predict the threshold stress of crack initiation in the experiment. It was found that the predicted threshold stress value of crack initiation is the same under different applied constant loads, which indicates that the crack initiation stress is independent of the applied load at this test condition. Through observation of samples with an applied load of 600MPa and different exposed time, it was found that the crack initiation stress decreases with the extension of exposed time, which is consistent with the results observed in parallel samples in the literature, indicating that this method predicts crack initiation stress is reliable. The finite element simulation calculation was used to discuss the feasible mechanism of this method. This test method provides an efficient and fast method for in-depth study of the service degradation of materials and predicting the service safety of components.

Keywords: Stress corrosion cracking, threshold stress, small tapered specimen, high throughput characterization