Within the framework of a Joint Industrial Project (JIP) sponsored by several petroleum companies, the behavior of several Precipitation Hardened (PH) Ni-based alloys with respect to Hydrogen Induced Stress Cracking (HISC) resistance was studied using the Slow Strain Rate Tensile (SSRT) test method under hydrogen charging conditions. The experimental conditions included a 0.5M sulfuric acid solution at 5 mA/cm2 and at 40°C at a strain rate of 10-6 sec-1. A round robin was performed that highlighted the need to measure the effective strain rate of the specimen during the elastic part of the SSRT test, the cell configuration, the current density, the gas cap composition, were all studied to determine the effects on the results. Once the test conditions had been optimized, the study of different industrial heats was carried out on specimens sampled in three locations, 120 degrees apart and at mid radius. It was found that sampling different areas could lead to changes in the test results, resulting mainly from microstructural variances at different locations of the bar. The results generated in this program could then be studied by relating plastic elongation obtained under CP as well as cracking mode and microstructure compliance with the API 6A CRA standard.

Subject
Scanning electron microscopy, Test methods, Materials, Electrochemical cells, Hydrogen concentration, Materials performance, Microstructure, Precipitates, Nickel based alloys, Plastics, Elongation, Grain boundary, Samples
Keywords:
SSRT, HISC, Precipitation Hardened Ni-based alloys
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2019
Association for Materials Protection and Performance (AMPP)
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