Recycling of alpha-titanium technological scrap for exhaust system parts manufacturing

In this paper, five different titanium alpha alloys obtained by investment casting, and recycled titanium scrap which originated from other technological operations have been studied in order to investigate their basic properties and to determine the industrial feasibility of the manufacturing of recycled titanium exhaust system parts on an industrial scale. Chemical analysis after a first and a second melting step, a complete mechanical characterization and oxidation resistance test at different temperatures have been performed. The direct influence of the alloying elements, like Si and Al, on the oxidation resistance of titanium at high temperature has been studied, in order to identify the best blended alloy for investment casting applications. An important aspect which has also been evaluated is the increase of oxygen content after remelting of the blend alloys and its impact on the mechanical properties. Results show that it is possible to use the identified blend alloys to obtain cast components suitable for applications requiring exposure at a temperature up to 700 °C, and for the Si-richer blends, up to 800 °C.