Oxidation Behavior of Cast Alpha-Titanium Scrap Blends for Exhaust Systems Applications

摘要

In this paper, five different titanium alpha alloys obtained by investment casting, remelting titanium scrap originated by other technological processes (tube production,bending,deep drawing),have been studied in order to investigate their oxidation resistance at different temperature in the 700-800°C range. The direct influence of the alloying elements,like Silicon and Aluminum,on the oxidation resistance of titanium at high temperature has been studied,in order to identify the best blended alloy for manufacturing high performance exhaust systems components. Another important facet which has been taken into account is the influence of surface finishing related to the oxide layer growth and morphology. The results of the laboratory tests clearly show that the specimens submitted to oxidation test at 700 °C present the formation of a protective scale of oxide rich in SiO2 and A12O3 which limits the diffusion of oxygen into the base metal. Above 800°C ,the scale of oxide underwent a significant thickness increase,accompanied by a decrease of its adhesion to the Ti substrate. Su mm arizing, the performed analysis on oxidized titanium alpha alloys obtained by investment casting, allow asserting that controlling the percentage of specific alloying elements like Si and Al the oxidation resistance of these titanium alloys can be significantly improved. These results show the possibility of tailoring blended titanium alloys dedicated to high temperature applications,obtained by remelting technological scrap.