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The Effect of Coating on Alloy AISI 304 at High Temperature on Fatigue Resistance | ||
| Rafidain Journal of Science | ||
| Article 9, Volume 22, Issue 8, 2011, Pages 107-118 PDF (0 K) | ||
| DOI: 10.33899/rjs.2011.30179 | ||
| Authors | ||
| Moayad Mohammad* ; Yahya A. Salman | ||
| Department of Physics College of Science University of Mosul | ||
| Abstract | ||
| In This research the effect of metallic coating namely, aluminizing and chromizing on fatigue resistance of austinitic alloy AISI 304 has been studied. The metallic coating were conducted using a cementation method at 1000°C such coatings are used to protect the alloys in severe corrosion environments. The results obtained showed some small reduction in fatigue life of aluminized alloy when compared to a bare alloy, this reduction could be attributed to formation of intermetallic compound Fe- Al and Ni-AI on the surface of aluminized specimens. The intermetallic compound could be suffer a phase transformation when treated at 1050°C, as a result of rediffusion processes, that can be promoting the fatigue resistance. However a significant deteration in fatigue life were accounted for chromizing corresponds to formation of a brittle FeCr and NiCr solid solution on the specimens surface, although some small increases in fatigue life was also detected after heat treatments at 1050°C, this is could be belong to the rediffusion of chromium element down word through the specimen. Generally, both types of coatings leads to a phase transformation of the base alloy itself from austenite to ferrite, this transformation could be occurred either because of Ni depletion to contribute in the formation of surface layer ( coating matrix ), as in case of aluminizing, or because of significant increases of chromium concentration in the base alloy, as in the case of chromizing, which can also leads to formation of intergranular chromium carbides, the formation of chromium carbides can increases the brittleuess, as well as, can offards an easy way for crack propagation in fatigue test. However, the results proved that the best fatigue resistance was obtained, when a base alloy itself treated at 1050°C the slowly cooled to obtain a single form of austenitic phase . | ||
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