Performance, tolerance and cost of TiAl passenger car valves

It is the clear goal of all new engine development to improve efficiency and to reduce emissions. Big efforts are taken and one field of exhaustive research is the valve train of four-stroke SI engines. It is seen as a proven benefit to replace existing cam shafts with so called cam-less systems, however, those require light weight engine valves. Amongst other materials, valves made from intermetallic TiAl γ-alloys were developed in recent history. Those had to fulfil a performance evaluation as well as meet cost objectives. As costs are strongly related to the production process and the required tolerances, a rough outline about these topics is also given.