Shot Material and Shot Peening Method

Abstract

A method of shot peening a workpiece comprising projecting metal alloy particles at a workpiece wherein said metal alloy particles comprises Fe in combination with B, C, Cr and Nb, wherein the Fe is present at a level of greater than 50.0 atomic percent. The metal alloy particles have a Vickers Hardness (HV) of at least 1150 and an elastic modulus of greater than 200 GPa.

1 . A method of shot peening a workpiece comprising projecting metal alloy particles at a workpiece wherein said metal alloy particles comprises Fe in combination with B, C, Cr and Nb, wherein the Fe is present at a level of greater than 50.0 atomic percent wherein said metal alloy has a Vickers Hardness (HV) of at least 1150 and an elastic modulus of greater than 200 GPa. 
     
     
         2 . The method of  claim 1  wherein said metal alloy has a HV of 1150-1400. 
     
     
         3 . The method of  claim 1  wherein said metal alloy has an elastic modulus in the range of greater than 200 GPa to 350 GPa. 
     
     
         4 . The method of  claim 1  wherein said metal alloy comprises:
 Fe: 59.0-64.0 at. % 
 B: 17.5-18.8 at. % 
 C: 4.4-5.1 at. % 
 Cr: 12.7-13.1 at. % 
 Nb: 1.4-1.7 at. %. 
 
     
     
         5 . The method of  claim 1  wherein 95% of the particles have a size in the range of 40 μm to 250 μm. 
     
     
         6 . The method of  claim 1  wherein the particles have the following particle size distribution:
 D10: 50 μm 
 D50: 80 μm 
 D90: 150 μm. 
 
     
     
         7 . The method of  claim 1  wherein the weight fraction of particles of less than 75 microns is less than or equal to 7.0%, after projection of said particles onto said workpiece. 
     
     
         8 . The method of  claim 1  wherein the shot is projected at a metal substance having a HV in the range of 500 to 1000. 
     
     
         9 . The method of  claim 1  wherein said alloy includes α-Fe and/or γ-Fe and one or more of the following:
 (1) complex borides; 
 (2) complex carbides; or 
 (3) borocarbides. 
 
     
     
         10 . The method of  claim 1  wherein said alloy comprises:
 Fe: 58.0-65.0 at. % 
 B: 14.0-19.0 at. % 
 C: 4.4-5.5 at. % 
 Cr: 7.0-13.5 at. % 
 Nb: 1.4-3.5 at. %. 
 
     
     
         11 . The method of  claim 1  wherein the particles have the following particle size distribution:
 D10: 50-100 μm 
 D50: 100-150 μm 
 D90: 150-200 μm 
 
     
     
         12 . The method of  claim 1  wherein said particles, when projected at a pressure of 0.55 MPa, to a preconditioned steel workpiece, indicate a mass loss associated with the fraction of particles less than 75.0 μm, after a time period of 18.0 hours, of less than or equal to 20.0%. 
     
     
         13 . The method of  claim 1  wherein said particles, when projected at a pressure of 0.28 MPa, to a preconditioned steel workpiece, indicate a mass loss associated with the fraction of particles of less than 75.0 μm, after a time period of 6 hours, of less than or equal to 15.0%. 
     
     
         14 . The method of  claim 1  wherein said workpiece comprises one of a gear part, cam, camshaft, clutch spring, coil spring, connecting rod, crankshaft, gearwheel, leaf spring, suspension spring, threads, rock drill, turbine blades or engine valve spring. 
     
     
         15 . Shot peening material comprising metal alloy particles containing Fe in combination with B, C, Cr and Nb, wherein the Fe is present at a level of greater than 50.0 atomic percent wherein said metal alloy has a Vickers Hardness (HV) of at least 1150 and an elastic modulus of greater than 200 GPa. 
     
     
         16 . Shot peening material of  claim 15  wherein said metal alloy has a HV of 1150-1400. 
     
     
         17 . Shot peening material of  claim 15  wherein said metal alloy has an elastic modulus in the range of greater than 200 GPa to 350 GPa. 
     
     
         18 . Shot peening material of  claim 15  wherein said metal alloy comprises:
 Fe: 59.0-64.0 at. % 
 B: 17.5-18.8 at. % 
 C: 4.4-5.1 at. % 
 Cr: 12.7-13.1 at. % 
 Nb: 1.4-1.7 at. %. 
 
     
     
         19 . Shot peening material of  claim 15  wherein 95% of the particles have a size in the range of 40 μm to 250 μm. 
     
     
         20 . The shot peening material of  claim 15  wherein said alloy comprises:
 Fe: 58.0-65.0 at. % 
 B: 14.0-19.0 at. % 
 C: 4.4-5.5 at. % 
 Cr: 7.0-13.5 at. % 
 Nb: 1.4-3.5 at. %. 
 
     
     
         21 . The shot peening material of  claim 15  wherein the particles have the following particle size distribution:
 D10: 50-100 μm 
 D50: 100-150 μm 
 D90: 150-200 μm.