Under the Platinum Development Initiative, platinum-based alloys were being developed for high-temperature and special applications for good corrosion and oxidation resistance. Parts I–III of the present series of papers dealt with the development of the ternary and quaternary Pt alloys (–). In this final paper (Part IV), the corrosion behaviour of selected Pt alloys treated with sodium sulfate salt was compared with that of coated and uncoated CMSX-4
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nickel-based superalloy (NBSA). Scanning electron microscopy (SEM) results showed that protective alumina scales of different integrities formed on the Pt alloys, whereas the NBSAs failed rapidly even with an additional Ptaluminide protective coating. Although there were pits on the Pt alloys, they were minor and not visible to the unaided eye. The potential for application of these Pt alloys in the aerospace gas turbine industry was assessed based on their hot corrosion performance.
Purpose -To evaluate the corrosion resistance of four different stainless steels often employed in hot end exhaust components. Design/methodology/approach -This paper evaluated the outcomes of the hot salt test and the cyclic oxidation test on four different stainless steels, used as hot end exhaust components. The specimens were analyzed by means of SEM for surface changes and the weight loss was considered. Findings -The general corrosion rate and pitting resistance under all the test conditions for hot end exhaust components indicated that 434 was by far the most corrosion resistant alloy, followed by 1.4509 and 321, and lastly 304 was the least corrosion resistant. In general, the ferritic stainless steels, especially 434, outperformed the austenitic ones under all the test conditions. Practical implications -The comparison of the corrosion resistance and rate, between the frequently used ferritic and austenitic stainless steels used in the exhaust system, gave a clear indication that the ferritic steels will provide prolonged service and this could be beneficial information to the manufacturers. Originality/value -A new approach to summarise the materials' behaviour and their relative performance in the tests performed was developed. This proposed summary of a number of corrosion indicators could serve as a relative guide to alloy selection for use in hot end automotive exhaust systems for both manufacturers and users.
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