Piston ring, especially the second pressure ring of a direct injection diesel engine, consists of a surface nitrided steel of relatively low chromium content

摘要

A piston ring consists of a surface nitrided steel of relatively low chromium content. A piston ring, for a direct injection diesel engine, is made of a steel which contains 0.4-0.8 wt.% C and 6-11 wt.% Cr and which has been surface nitrided at least at its slide surface. An Independent claim is also included for a piston ring combination, for a direct injection diesel engine, comprising (a) a first pressure ring of corrosion-free martensitic steel which contains 0.4-1.2 wt.% C and 11-18 wt.% Cr and which has, at least on its slide surface, a hardened surface layer comprising a nitride layer optionally coated with a PVD layer; and (b) a second pressure ring as described above.