Method of strengthening binder metal phase of sintered body

Abstract

Spherical shaped ejection particles are ejected against a surface of a sintered body including hard particles and a binder metal phase bonding the hard particles together, with a compressed gas at an ejection pressure of from 0.2 MPa to 0.6 MPa or at an ejection velocity of from 80 m/s to 200 m/s and the spherical ejection particles having a hardness not less than the hardness of the binder metal phase and that is a hardness of 1000 HV or less and being particles having an average particle diameter from 20 μm to 149 μm. Thus, plastic deformation resulting from such impact and the instantaneous temperature rise and cooling occurring at the impact sites micronizes the structure of the binder metal phase, causes a change to a dense structure, and imparts compressive residual stress thereto. This results in strengthening, and enables prevention of brittle fracture in the sintered body.

1 . A method of strengthening a binder metal phase of a sintered body, the binder metal phase strengthening method comprising:
 ejecting spherical shaped ejection particles against a surface of a sintered body that includes hard particles and a binder metal phase bonding the hard particles together, by ejecting the spherical shaped ejection particles together with a compressed gas at an ejection pressure of from 0.2 MPa to 0.6 MPa or at an ejection velocity of from 80 m/s to 200 m/s and the spherical ejection particles having a hardness that is not less than the hardness of the binder metal phase and that is a hardness of not more than 1000 HV and being particles of from 100 grit to 800 grit, having an average particle diameter of from 20 μm to 149 μm.   
     
     
         2 . The sintered body binder metal phase strengthening method of  claim 1 , wherein a sintered body employed as a treatment subject is a sintered body having a hard coating film coated on at least a portion of surface at a thickness of not more than 5 μm, and the ejection particles are ejected against the sintered body at the portion of the surface coated with the hard coating film. 
     
     
         3 . The sintered body binder metal phase strengthening method of  claim 1 , wherein the ejection particles are metal particles, ceramic particles, or a mixture of metal particles and ceramic particles. 
     
     
         4 . The sintered body binder metal phase strengthening method of  claim 1 , wherein a hardness of the ceramic particles employed is not more than 800 HV. 
     
     
         5 . The sintered body binder metal phase strengthening method of  claim 2 , wherein the ejection particles are metal particles, ceramic particles, or a mixture of metal particles and ceramic particles. 
     
     
         6 . The sintered body binder metal phase strengthening method of  claim 2 , wherein a hardness of the ceramic particles employed is not more than 800 HV. 
     
     
         7 . The sintered body binder metal phase strengthening method of  claim 3 , wherein a hardness of the ceramic particles employed is not more than 800 HV. 
     
     
         8 . The sintered body binder metal phase strengthening method of  claim 5 , wherein a hardness of the ceramic particles employed is not more than 800 HV.