Shot Material and Shot Peening Method

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.