Effect of Aging Temperature on the Microstructure, Local Mechanical Properties, and Wear Behavior of a UNS S32750 Super
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Effect of Aging Temperature on the Microstructure, Local Mechanical Properties, and Wear Behavior of a UNS S32750 Super Duplex Stainless Steel Bouzid Maamache, Billel Cheniti, Brahim Belkessa, Karima Tahar-chaouch, and Ramdhane Kouba Submitted: 2 September 2020 / Revised: 28 October 2020 / Accepted: 1 November 2020 In this paper, the effect of aging temperature on the microstructure, local mechanical properties and wear behavior of a UNS S32750 super duplex stainless steel is investigated. A massive preferential precipitation of r phase and Cr2N is detected at the periphery of ferrite with an increase in their extent as aging temperature increases. Simultaneously, the d phase decomposition is accentuated with temperature and reaches its maximum at 850 °C. This behavior results in an enhancement in hardness and YoungÕs modulus accompanied by a higher plasticity ratio. The wear resistance of the aged samples is investigated in terms of friction coefficients and wear rates against two counterparts. The wear performance follows r phase presence, the higher r phase extent, the higher the wear resistance. It is found that the change in wear mechanisms in the 850 °C aged samples from abrasive against AISI-304L counterpart to adhesive-oxidative against Al2O3 counterpart is responsible in the increase in wear resistance. Keywords
2507 SDSS, aging temperature, microstructure, nano-indentation, precipitates, wear resistance
1. Introduction Super duplex stainless steels (SDSSs) with dual-phase ferrite–austenite microstructure have raised much interest as structural materials in research and industrial fields (Ref 1). Thanks to their attractive mechanical properties, (high hardness, strength and ductility) and good resistance to the local pitting and stress cracking corrosion, especially in chloride environment (Ref 2, 3), SDSSs are widely designed as a solution in the marine, electrochemical industries and lightweight structures (Ref 4). Nevertheless, the above outstanding properties are strongly dependent on the manufacturing processes and the thermal history of the SDSS materials (Ref 5). It is well-known that annealing treatment of 2507 SDSS at temperature bellow 1000 C leads to the phase decomposition of ferrite phase (d) to sigma (r) phase and carbides which results in the increase in Ni concentration in the surrounding material, consequently, the formation of secondary austenite (c2) (Ref 6). These precipitates deteriorate the toughness of the SDSS and decrease its corrosion performance by stimulating local corrosion attack around the precipitates already formed (Ref 5). Nilsson (Ref 7) highlighted that at temperature range
Bouzid Maamache, Billel Cheniti, and Brahim Belkessa, Research Center, Industrial Technologies CRTI, P.O. Box 64, Che´raga, Algeria; Karima Tahar-chaouch, De´partement de me´canique Faculte´ de Technologies, Universite´ Blida 1, BP 270 route de Soumaa Blida, Blida, Algeria; and Ramdhane Kouba, Laboratoire de Technologie des Mate´riaux, De´partement SDM, Faculte´d
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