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7178 |
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Wednesday, June 22, 2022, Saal Brüssel 2:00 PM Brazing of demanding materials and joints |
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Vacuum brazing of super duplex stainless steels and corrosion resistance |
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Nicholas Ludford / TWI Ltd., Great Britain Konstantinos Georgilas* / TWI Ltd, United Kingdom Paul Brooker/ TWI Ltd, United Kingdom James Redman/ TWI Ltd, United Kingdom |
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Super duplex stainless steels (SDSS) are high performance materials that combine excellent mechanical properties with outstanding corrosion performance. SDSS material acquires its properties through the balancing of the austenite and ferrite in equal proportions (50/50). Corrosion resistance is provided by the large content in chromium, nickel, molybdenum and nitrogen. Due to the large number of alloying elements SDSS have complex metallurgical properties which make them extremely sensitive to thermal processing and hence vacuum brazing. In the current work we have investigated the effect of vacuum brazing cycles on the corrosion resistance (G48 test methodology) of the parent material as well as the braze joint. Specifically we will present the effect of different vacuum heat treatment cycles on the corrosion performance of the bar and tube parent material. The most promising heat treatment cycles were then investigated with respect to their viability to produce brazed joints using a variety of braze alloys e.g. Ni613, Ni620 & Ni630. The performance of the brazed joints has then been characterised in terms of corrosion, microstructure and mechanical properties. |