VALVE MATERIALS FOR COMBUSTION ENGINES

An overview is being given on production numbers, requirements and pro perties of valve materials. Their development from the beginning till today's state of the art is reviewed with a focus on Chromium-Manganes e-Nitrogen-alloys. Valve materials are grouped by the criteria of dens ity - heavy, lightweight - and alloying elements. The multiple stresse s of the material in the valve are being met with a few standardised g rades and specific ways of manufacture. The path of the material from bar stock to the finished valve is being followed. Engine development in the past decades increased the load on the valves which could be me t by continuously developing their structural strength. Also the stren gth of all valve materials could be raised to nominal strength above 1 100 Mpa by applying specific methods. Higher strength at the surface i s being effectuated by work hardening effects. The technology to incre ase reliability of hollow valves and new aspects of valve seat facing including residual stress is explicity discussed. General aspects of a lloy utilisation is followed by a discussion of lightweight valve mate rials as Titanium alloys, intermetallic Titaniumaluminide alloys and c eramic materials, spec. Silicon Nitride, which all have a potential as forthcoming valve materials capable of reducing fuel consumption of t he engines.