CORROSION BEHAVIOUR OF HIPED AND CAST STELLITE ALLOYS IN A CO2-CONTAINING SEAWATER ENVIRONMENT

摘要

Stellite alloys are widely used in many industries for their strength, corrosion and wear resistance. In order to further improve their mechanical properties, Hot isostatic pressing (HIPing) techniques have been developed and a great advantage of the HIPing process is that extensive reactions between phases in composite are usually avoided because of the low processing temperatures used. How HIPing affects aqueous corrosion properties is largely unknown. Corrosion in CO2 environments is considered a very serious problem in the oil and gas industry. In this article, results from tests on HIPed and Cast Stellite alloys from a study carried out in seawater and CO2-saturated seawater are reported. electrochemical methods are used to assess their corrosion behaviour. Potentiodynamic tests were carried out in artificial seawater and CO2-saturated seawater at different temperatures. The critical breakdown temperature (CBT) was investigated for all materials in seawater and CO2-saturated seawater. With the exception of Stellite 706, the HIPed Stellite alloys showed better corrosion resistance than their cast counterparts over the entire temperature range and in different environments. The link between microstructure and corrosion behaviour is discussed followed by some implications from this study.