Valve train component for an internal combustion engine, and method of making same

Abstract

In order to provide a wear-resistant member which is excellent in wear resistance and pitting resistance, a valve train component is subjected to oxidation treatment to adjust its surface hardness to a preliminary value in a range between 550 and 800, followed by shot peening of at least a contact surface, to adjust the surface hardness to a value in a range between 800 and 1000. In a valve spring retainer, the contact surface is a seating surface against which a valve spring abuts. In a valve lifter, the contact surface is a sliding surface against which a cam lobe abuts. The components subject to the oxidation treatment are each made of a titanium alloy having an alloy composition including from 0.5 to 1.5 wt. % of Fe, from 0.2 to 0.5 wt. % of O and the balance of Ti and unavoidable impurities.

1 . A wear-resistant valve train component member formed from a material comprising titanium, said valve train component member being a product of a process including steps of:
 case-hardening at least one surface of said member, designated as an abutting surface configured for abutting contact with another member, by oxidation treatment to adjust a surface hardness Hmv (load: 0.1 kg) of said surface to an oxidized value in a range between 550 and 800 Hmv;   followed by shot peening said abutting surface to adjust the surface hardness Hmv (load: 0.1 kg) of said surface to a final value in a range between 800 and 1000 Hmv.   
   
   
       2 . A wear-resistant valve train component according to  claim 1 , wherein the shot peening is performed using media having a particle size in a range from about 0.03 mm to about 0.1 mm. 
   
   
       3 . A wear-resistant valve train component according to  claim 1 , wherein an α-case layer, having a thickness in a range from about 5 μm to about 20 μm, is formed by the oxidation treatment. 
   
   
       4 . A wear-resistant valve train component according to  claim 1 , wherein the shot peening is carried out with a coverage of from 100 to 500%. 
   
   
       5 . A wear-resistant valve train component member according to  claim 1 , wherein the member is made of a titanium alloy having, as an alloy composition, from 0.5 to 1.5 wt. % of Fe, from 0.2 to 0.5 wt. % of O and the balance of Ti and unavoidable impurities. 
   
   
       6 . A wear-resistant valve train component member according to  claim 1 , wherein the member is a valve spring retainer having an abutting surface on which a valve spring abuts. 
   
   
       7 . A wear-resistant valve train component member according to  claim 1 , wherein the member is a valve lifter having an abutting surface on which a cam lobe slides. 
   
   
       8 . A wear-resistant valve train component member formed from a material comprising titanium, said valve train component member being a product of a process including steps of:
 case-hardening at least one surface of said member, designated as an abutting surface configured for abutting contact with another member, by oxidation treatment to adjust a surface hardness Hmv (load: 0.1 kg) of said surface to an oxidized value in a range between 550 and 800 Hmv;   followed by shot peening said abutting surface to adjust the surface hardness Hmv (load: 0.1 kg) of said surface to a final value in a range between 800 and 1000 Hmv;   wherein the shot peening is performed using media having a particle size in a range from about 0.03 mm to about 0.1 mm;   and wherein an α-case layer, having a thickness in a range from about 5 μm to about 20 μm, is formed by the oxidation treatment.   
   
   
       9 . A wear-resistant valve train component according to  claim 8 , wherein the shot peening is carried out with a coverage of from 100 to 500%. 
   
   
       10 . A wear-resistant valve train component member according to  claim 9 , wherein the member is made of a titanium alloy having, as an alloy composition, from 0.5 to 1.5 wt. % of Fe, from 0.2 to 0.5 wt. % of O and the balance of Ti and unavoidable impurities. 
   
   
       11 . A wear-resistant valve train component member according to  claim 8 , wherein the member is either a valve spring retainer or a valve lifter. 
   
   
       12 . A method of case-hardening a valve train component member formed from a material comprising titanium, said method including the steps of:
 case-hardening at least one surface of said member, designated as an abutting surface configured for abutting contact with another member, by oxidation treatment to adjust a surface hardness Hmv (load: 0.1 kg) of said surface to an oxidized value in a range between 550 and 800 Hmv; an subsequently, shot peening said abutting surface to adjust the surface hardness Hmv (load: 0.1 kg) of said surface to a final value in a range between 800 and 1000 Hmv.   
   
   
       13 . A method of case-hardening a valve train component member according to  claim 12 , wherein the shot peening is performed using media having a particle size in a range from about 0.03 mm to about 0.1 mm. 
   
   
       14 . A method of case-hardening a valve train component member according to  claim 12 , wherein an α-case layer, having a thickness in a range from about 5 μm to about 20 μm, is formed by the oxidation treatment. 
   
   
       15 . A method of case-hardening a valve train component member according to  claim 12 , wherein the shot peening is carried out with a coverage of from 100 to 500%. 
   
   
       16 . A method of case-hardening a valve train component member according to  claim 12 , wherein the member is made of a titanium alloy having, as an alloy composition, from 0.5 to 1.5 wt. % of Fe, from 0.2 to 0.5 wt. % of O and the balance of Ti and unavoidable impurities. 
   
   
       17 . A method of case-hardening a valve train component member according to  claim 12 , wherein the member is a valve spring retainer having an abutting surface on which a valve spring abuts. 
   
   
       18 . A method of case-hardening a valve train component member according to  claim 12 , wherein the member is a valve lifter having an abutting surface on which a cam lobe slides.