| 摘要 |
A combined oil ring is comprised of paired upper and lower side rails, and a spacer expander. The side rails are made of martensitic stainless steel and are subjected to gas nitriding. The spacer expander is made of austenitic stainless steel, and has a soft-nitrided layer formed as the under coating, and has a hard film formed by an ion plating on the soft-nitrided layer at the outer circumferential surface. The hard film has a Vicker's hardness of HV1300 to HV2200 and a thickness of 1 mu m to 50 mu m. The hard film is a film of a mixture of CrN and Cr2N or a film of a mixture of CrN, Cr2N and Cr, and the crystal of CrN has a preferred orientation (200). <IMAGE> |
