Casing for rotating piston engine - inner surface has wear resistant coating covered by softer layer

摘要

The inner surface of rotating piston engine casing has a hard and wear resisting coating which is on its turn covered by a layer of a more soft material. The thickness of this last layer is bigger than the radially measured maximum amplitude of free space existing, before any wearing of the soft layer takes place, between a rotor ring sliding against thw layer and the latter's surface, due to distortions, particularly of thermal origin, occuring when the engine is working. The hardness of the hard coating is greater than 400 Vickers while the softer one's hardness is less than 150 Vickers.