Cutting elements including undulating boundaries between catalyst-containing and catalyst-free regions of polycrystalline superabrasive materials and related earth-boring tools and methods
Cutting elements for earth-boring tools may include a substrate and a polycrystalline superabrasive material secured to the substrate. The polycrystalline superabrasive material may include a first region including catalyst material in interstitial spaces among interbonded grains of the polycrystalline superabrasive material. A second region at least substantially free of catalyst material in the interstitial spaces among the interbonded grains of the polycrystalline superabrasive material may be located adjacent to the first region. An undulating boundary defined between the first region and the second region may include bumps and dimples formed by crests and troughs of a repeating pattern of concentric circles encircling a longitudinal axis of the cutting element.
1. A cutting element for an earth-boring tool, comprising:
a substrate; and
a polycrystalline superabrasive material secured to the substrate, the polycrystalline superabrasive material comprising:
a first region including catalyst material in interstitial spaces among interbonded grains of the polycrystalline superabrasive material; and
a second region at least substantially free of catalyst material in the interstitial spaces among the interbonded grains of the polycrystalline superabrasive material, an undulating boundary being defined between the first region and the second region, the undulating boundary comprising crests and troughs of a repeating pattern of concentric circles encircling a longitudinal axis of the cutting element;
wherein the undulating boundary is free of planar portions and wherein a wavelength of the undulating boundary is smaller proximate to a periphery of the cutting element than the wavelength of the undulating boundary proximate to the longitudinal axis.
2. The cutting element of claim 1 , wherein a plane defined by an average height of the undulating boundary with respect to a plane of an interface surface between the substrate and the polycrystalline superabrasive material is parallel to the plane of the interface surface.
3. The cutting element of claim 1 , wherein at least one cross-section of the undulating boundary is sinusoidal.
4. The cutting element of claim 1 , wherein a portion of the polycrystalline superabrasive material in the second region is in a compressive stress state.
5. The cutting element of claim 4 , wherein the portion of the polycrystalline superabrasive material in the compressive stress state is located between crests of the undulating boundary.
6. The cutting element of claim 1 , wherein the peaks and troughs of the undulating boundary exhibit an average amplitude of between 40 μm and 50 μm and an average wavelength of between 100 μm and 1000 μm.
7. The cutting element of claim 1 , wherein the polycrystalline superabrasive material comprises a concavity proximate the longitudinal axis of the cutting element.
8. The cutting element of claim 1 , wherein a crest-to-trough centerline of the undulating boundary also undulates.
9. An earth-boring tool, comprising:
a body; and
a cutting element secured to the body, the cutting element comprising:
a substrate secured to the body; and
a polycrystalline superabrasive material secured to the substrate, the polycrystalline superabrasive material comprising:
a first region including catalyst material in interstitial spaces among interbonded grains of the polycrystalline superabrasive material; and
a second region at least substantially free of catalyst material in the interstitial spaces among the interbonded grains of the polycrystalline superabrasive material, an undulating boundary being defined between the first region and the second region, the undulating boundary comprising crests and troughs of a repeating pattern of concentric circles encircling a longitudinal axis of the cutting element;
wherein the undulating boundary is free of planar portions and wherein a wavelength of the undulating boundary is smaller proximate to a periphery of the cutting element than the wavelength of the undulating boundary proximate to the longitudinal axis.
10. The earth-boring tool of claim 9 , wherein a plane defined by an average height of the undulating boundary with respect to a plane of an interface surface between the substrate and the polycrystalline superabrasive material is parallel to the plane of the interface surface.
11. The earth-boring tool of claim 9 , wherein at least one cross-section of the undulating boundary is sinusoidal.
12. The earth-boring tool of claim 9 , wherein the peaks and troughs of the undulating boundary exhibit an average amplitude of between about 40 μm and 50 μm and an average wavelength of between 100 μm and 1000 μm.
13. The earth-boring tool of claim 9 , wherein the polycrystalline superabrasive material comprises a concavity proximate the longitudinal axis of the cutting element.
14. The earth-boring tool of claim 9 , wherein a crest-to-trough centerline of the undulating boundary also undulates.
15. A method of preparing a cutting element for an earth-boring tool, comprising:
retaining catalyst material within interstitial spaces among interbonded grains in a first region of a polycrystalline superabrasive material, the polycrystalline superabrasive material being secured to a substrate; and
at least substantially completely removing catalyst material from interstitial spaces among interbonded grains in a second region of the polycrystalline superabrasive material, to form an undulating boundary comprising crests and troughs of a repeating pattern of concentric circles encircling a longitudinal axis of the cutting element between the first region and the second region, wherein the undulating boundary is free of planar portions and wherein a wavelength of the undulating boundary is smaller proximate to a periphery of the cutting element than the wavelength of the undulating boundary proximate to the longitudinal axis.
16. The method of claim 15 , wherein at least substantially completely removing catalyst material from the interstitial spaces among the interbonded grains in the second region of the polycrystalline superabrasive material comprises rendering a plane defined by an average height of the undulating boundary with respect to a plane of a surface of the substrate adjacent to the polycrystalline superabrasive material parallel to the plane of the surface of the substrate adjacent to the polycrystalline superabrasive material.
17. The method of claim 15 , wherein at least substantially completely removing catalyst material from the interstitial spaces among the interbonded grains in the second region of the polycrystalline superabrasive material comprises rendering at least one cross-section of the undulating boundary sinusoidal.
18. The method of claim 15 , wherein at least substantially completely removing catalyst material from the interstitial spaces among the interbonded grains in the second region of the polycrystalline superabrasive material comprises inducing a compressive residual stress in a portion of the polycrystalline superabrasive material in the second region.
19. The method of claim 15 , wherein at least substantially completely removing catalyst material from the interstitial spaces among the interbonded grains in the second region of the polycrystalline superabrasive material comprises rendering an average amplitude of the peaks and troughs of the undulating boundary to be between 40 μm and 50 μm and an average wavelength of the peaks and troughs of the undulating boundary to be between 100 μm and 1000 μm.
20. The method of claim 15 , further comprising forming a concavity in the polycrystalline superabrasive material proximate the longitudinal axis of the cutting element.