Piston ring

Abstract

Provided is a piston ring ( 10 ) comprising a sliding surface ( 11 ) covered with a Cr—B—V—N alloy film ( 3 ), wherein a B content is within a range of 0.1-1.5 mass % inclusive, a V content is within a range of 0.05-1 mass % inclusive, and a ratio [B content/V content] is within a range greater than 1 and 30 or less, thereby achieving a piston ring ( 10 ) having higher wear resistance, cracking resistance, and peeling resistance. This alloy film ( 3 ) preferably further includes Ti, the Ti content being within a range greater than 0 mass % and 8 mass % or less. Such a piston ring ( 10 ) is preferably mounted on an engine that uses an alcohol fuel or an alcohol-containing fuel.

What is claimed is: 
     
       1. A piston ring comprising a sliding surface covered with a Cr—B—V—Ti—N alloy film;
 a B content being within a range of 0.1-1.5 mass % inclusive, a V content being within a range of 0.05-1 mass % inclusive, and a ratio [B content/V content] is greater than 1 and is 30 or less, wherein 
 the Ti content is within a range of 1.9-8 mass %, the Cr content is within a range of 55-61 mass % inclusive, and the N content is within a range of 32-40 mass % inclusive. 
 
     
     
       2. The piston ring according to  claim 1 , wherein
 the piston ring is configured to be mounted on an engine that uses an alcohol fuel or an alcohol-containing fuel. 
 
     
     
       3. The piston ring according to  claim 1 , wherein:
 the alloy film is less dense on a base material side than a front surface side of the piston ring. 
 
     
     
       4. The piston ring according to  claim 1 , wherein
 a nitriding treated layer or a metal underlayer is provided as an underlayer of the alloy film. 
 
     
     
       5. A piston ring comprising a sliding surface covered with a Cr—B—V—N alloy film;
 a B content being within a range of 0.1-1.5 mass % inclusive, a V content being within a range of 0.05-1 mass % inclusive, a ratio [B content/V content] is greater than 1 and is 30 or less, 
 wherein the alloy film has a wear rate between 0.17 to 0.63, for 1 as a wear rate of a Cr-2 mass % B—N tertiary alloy film, and has a high wear resistance. 
 
     
     
       6. The piston ring according to  claim 5 , wherein
 the piston ring is configured to be mounted on an engine that uses an alcohol fuel or an alcohol-containing fuel. 
 
     
     
       7. The piston ring according to  claim 5 , wherein
 the alloy film is less dense on a base material side than a front surface side of the piston ring. 
 
     
     
       8. The piston ring according to  claim 5 , wherein
 a nitriding treated layer or a metal underlayer is provided as an underlayer of the alloy film.