51312-01291-COMPARISON OF HYDROGEN SOLUBILITY AND DIFFUSIVITY IN 2.25CR-1MO AND 2.25CR-1MO-V STEELS: CONSEQUENCE

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Product Number: 51312-01291-SG

ISBN: 01291 2012 CP

Author: Sylvain Pillot

Publication Date: 2012

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For some year conventional 225Cr1Mo grade is less and less used for the fabrication of heavy refining reactors and replaced with 225Cr1MoV grade which offer much better mechanical properties at high temperatures. This change also offers large benefits on Hydrogen Induced Disbonding (HID) resistance due to large differences in hydrogen solubility and diffusion behaviour between the two grades. Hydrogen trapping ability of 225Cr1MoV is also an important parameter to take into consideration. This paper proposes to explain the differences between the two previously cited grades when facing gaseous hydrogen and then the consequence on HID performance. This demonstration is based both on actual hydrogen diffusion and solubility laws measurements hydrogen content profile simulations and actual HID tests to validate the conclusions. Disbonding tests are very often required during fabrication of hydro-treating vessels. This qualification test permits to assess the quality of the stainless steel overlay deposit procedure. As it is difficult to make the link between the testing conditions and the actual service conditions in the reactor wall studies were performed in the past and transferred into API 934-A recommended practice to better fit the test parameters to severity of actual field conditions and then avoid excessive safety.