HASTELLOY C-22HS is a nickel-chromium-molybdenum superalloy, featuring high corrosion resistance. The necessary aging treatment performed to increase the alloy hardness also leads to a decrease in the corrosion resistance. The aim of this work is to find a heat treatment which leads to a good compromise between these two characteristics. Additionally, welding is required in many of the applications of this alloy. Shielded metal arc welding (SMAW) is performed using the electrode ENiCrMo-13 by Fondinox. The effect of four different heat treatments were studied. All the samples were prepared to be analysed from the point of view of metallography, macro-hardness (Rockwell), micro-hardness (Vickers) and corrosion resistance. Concerning the last one, both a visual analysis and the estimation of the corrosion velocity were performed for a correct analysis of the behaviour of the two different alloys. All tests revealed that the galvanic contact did not significantly affect the results of the tests. Two heat treatments were found to be satisfying for the alloy applications.
HASTELLOY C-22HS è una superlega nichel-cromo-molibdeno caratterizzata da un’alta resistenza a corrosione. Questa resistenza cala di efficacia dopo l’invecchia\-mento, necessario per aumentarne la durezza. Lo scopo di questo studio è trovare un buon compromesso tra le due caratteristiche. Inoltre, il pezzo necessita di essere saldato in molte sue applicazioni. Tale processo è effettuato dalla compagnia Fondinox attraverso la saldatura a elettrodo rivestito (SMAW) usando l’elettrodo ENiCrMo-13. Sono stati analizzati gli effetti di quattro trattamenti termici. Tutti i campioni sono stati preparati per essere studiati dal punto di vista metallografico, della macro-durezza (Rockwell), della micro-durezza (Vickers) e della resistenza a corrosione. Di quest’ultima, l’analisi è stata sia visiva sia quantitativa per avere dei risultati completi sulla risposta delle due leghe. I test hanno dimostrato che il contatto galvanico non ha influenzato gli esiti. Due trattamenti termici sono stati trovati soddisfacenti per l’applicazione della lega saldata.
Study of hardness and corrosion resistance of welded HASTELLOY C-22HS after different heat treatments
SILVA, GIOVANNI
2016/2017
Abstract
HASTELLOY C-22HS is a nickel-chromium-molybdenum superalloy, featuring high corrosion resistance. The necessary aging treatment performed to increase the alloy hardness also leads to a decrease in the corrosion resistance. The aim of this work is to find a heat treatment which leads to a good compromise between these two characteristics. Additionally, welding is required in many of the applications of this alloy. Shielded metal arc welding (SMAW) is performed using the electrode ENiCrMo-13 by Fondinox. The effect of four different heat treatments were studied. All the samples were prepared to be analysed from the point of view of metallography, macro-hardness (Rockwell), micro-hardness (Vickers) and corrosion resistance. Concerning the last one, both a visual analysis and the estimation of the corrosion velocity were performed for a correct analysis of the behaviour of the two different alloys. All tests revealed that the galvanic contact did not significantly affect the results of the tests. Two heat treatments were found to be satisfying for the alloy applications.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/139981