Comparative study of erosion-corrosion performance on a range of stainless steels

Giourntas, Lampros Gerasimos and Hodgkiess, Trevor and Galloway, Alexander (2015) Comparative study of erosion-corrosion performance on a range of stainless steels. Wear, 332-333. pp. 1051-1058. ISSN 0043-1648

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    Abstract

    Erosion-corrosion is a material deterioration phenomenon that occurs in hydraulic machinery that handles aggressive slurries. Many industries attempt to mitigate this challenging feature by modifying the design of components and/or by selecting more erosion-corrosion resistant materials. The latter strategy often involves the selection of corrosion resistant alloys (CRAs), which exhibit good performance in many environments instead of using coating techniques to shield vulnerable materials such as carbon steels even if this increases the initial cost. An important attribute of the group of materials known as stainless steels is their capacity to resist high flow rates of many aqueous fluids. This contributes to the selection of various types of stainless steel in many engineering applications. Numerous studies have demonstrated that stainless steels display good erosion-corrosion performance in solid-free liquid impingement conditions [1,2]. This good behaviour is due to the ability of its chromium-rich, oxide passive film to resist breakdown even in rapidly flowing liquids and relatively high temperatures (up to 60oC)[3]. It is well known [4] that the durability of stainless steels decreases when suspended solids are present in the flowing liquid. On account of the diversity in composition, metallurgical structure and mechanical properties in stainless steels, it is of interest to compare the erosion-corrosion behaviour of a range of such materials in these more aggressive conditions. Many past investigations, however, have focused on individual grades of stainless steel, such as the standard austenitic UNS S31600/31603 [5–9] and similar austenitic stainless steel UNS S30400 [10–12]. When more than one stainless type has been studied they have usually comprised comparing two grades. Examples of such work are studies of UNS S31600 versus superaustenitic stainless steel [13,14], comparison of austenitic UNS S30400 with martensitic UNS S42000 [15], martensitic UNS S41000 against UNS S32760 [16] and duplex/superduplex versus UNS 31600 [17,18]. Some of these researchers have also demonstrated the superior erosion-corrosion resistance of stainless steels over carbon steels [16,17,19,20]. Another important feature, of many studies of the erosion corrosion behaviour of stainless steels (and other materials), has been the application of cathodic protection (CP) for the assessment of the potential benefits of the material durability and also in unravelling of erosion corrosion mechanisms [13,14,17,21]. The current study comprised a comparative investigation of four types of stainless steel in solid/liquid impingement conditions in a saline environment. The objectives of this study were firstly to obtain any evidence of the different performances of these four types of stainless steel, which might impact on material selection for the Offshore and Oil and Gas Industry. Also, the aim was to ascertain the extent to which the different metallurgical structures and chemical compositions of the steels influence the fundamental mechanisms of erosion-corrosion. A medium carbon steel was also included in the programme as a low-corrosion-resistant comparator. The testing environment has included free erosion corrosion conditions and also experiments involving the application of cathodic protection.