51316-7475-A New Cast Ni-Base Alloy Suitable for Severe Sour Service

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Product Number: 51316-7475-SG

ISBN: 7475 2016 CP

Author: Shankar Venkataraman

Publication Date: 2016

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The paper reports the recent findings on corrosion resistance of a new centrifugally cast corrosion resistant alloy (CRA) 46Ni-35Cr-9Mo towards severe sour gas environment (NACE MR0175/ISO 15156-3/Level VII). The centrifugal casting process allows extreme flexibility in terms of pipe manufacture with customized dimension (diameter wall thickness) as well as compositional freedom. 46Ni-35Cr-9Mo has been developed as an alternative to the conventional wrought UNS N08825 and UNS N06625 which are normally used for the most severe conditions in the On-/Offshore industry.The corrosion testing was carried out using autoclaves with four point bend samples the specimens were deflected (stressed) to the 100% of the actual yield strength (AYS) at 205 °C and the condition used was NACE MR0175/ISO 15156-3/Level VII with a pH of 5 and with a total exposure time of 720 h. The samples were taken from commercially centrifugally cast tubes. Two types of non passivated surface finish conditions were exposed (pulled bored and ground).The post-test examination did not reveal any cracking or corrosion i.e. the tested alloy fulfills the requirements for NACE MR0175/ISO 15156-3/Level VII. Consequently both the base material and the pull bored surfaces withstand the test conditions.