Method and system for improving the surface fracture toughness of brittle materials, and a cutting tool produced by such method
Methods of improving the wear resistance of a cemented carbide are provided. The methods include using fracture toughness as a selection criterion and selecting a cemented carbide which has a fracture toughness between about 6 and about 15 MPa·m 1/2 . Cutting tools and/or cutting tool inserts prepared using methods of the disclosure are also disclosed.
1. A method of improving the wear resistance of a cemented carbide, the method including:
selecting a cemented carbide which has a fracture toughness value between about 6 and about 15 MPa·m 1/2 ;
applying a sacrificial thermo-protective overlay to the cemented carbide; and
creating a toughened surface layer by inducing residual compressive stresses in a substrate of the cemented carbide using laser shock peening with a laser source capable of delivering between about 300 mJ to about 600 mJ to the cemented carbide at a pulse duration of between about 7 ns and about 10 ns (FWHM), a spot size between about 0.7 and about 1.2 mm, a power intensity of between about 7.5 and about 8.5 GW/cm 2 , and an overlap of between 0 and 90%, wherein the laser shock peening increases the fracture resistance to fatigue and stress corrosion cracking in the toughened surface layer as a result of an increase in fracture toughness while maintaining microhardness.
2. A method according to claim 1 , further comprising delivering between about 410 mJ to about 440 mJ to the substrate of the cemented carbide during laser shock peening.
3. A method according to claim 1 , wherein a pulse duration of about 8.6 ns (FWHM) is used during laser shock peening.
4. A method according to claim 1 , wherein a power Intensity of between about 7.5 and about 8.5 GW/cm 2 is used during laser shock peening.
5. A method according to claim 1 , wherein the sacrificial overlay is black PVC tape.
6. A method according to claim 1 , further comprising using an inertia containment medium during laser shock peening, wherein the inertial containment medium is a laser transparent medium.
7. A method according to claim 6 , wherein the laser transparent medium is water.
8. A method according to claim 1 , further comprising producing the cemented carbide by means of spark plasma sintering.
9. A method according to claim 1 , wherein the cemented carbide is selected from the group consisting of WC-X-YCo, NbC-X-YCo and NbC-X-YNi, where X is either one or a combination of Cr 3 C 2 , Mo 2 C, TiC, SiC, TaC and VC, and Y is the weight percentage of a binder phase and is in the range 4 to 16%.
10. A method according to claim 9 , wherein Y is the weight percentage of the binder phase and is in the range 8 to 10%.
11. A method of improving the wear resistance of a cemented carbide insert of a cutting tool using the method according to claim 1 .