Particulate mixtures for forming polycrystalline compacts and earth-boring tools including polycrystalline compacts having material disposed in interstitial spaces therein
View Patent ↗Polycrystalline compacts include smaller and larger hard grains that are interbonded to form a polycrystalline hard material. The larger grains may be at least about 33 times larger than the smaller grains. An interstitial material comprising one or more of a boride, a carbide, a nitride, a metal carbonate, a metal bicarbonate, and a non-catalytic metal may be disposed between the grains. The compacts may be used as cutting elements for earth-boring tools such as drill bits, and may be disposed on a substrate. A particulate mixture includes a first plurality of grains of hard material having a coating formed over the grains of hard material. The coating comprises at least one of a boride, a carbide, a nitride, a metal carbonate, a metal bicarbonate, and a non-catalytic metal. A second plurality of grains of hard material has a grain size at least 33 times larger than the first plurality.
1. A polycrystalline compact, consisting essentially of:
a plurality of grains of hard material, the grains comprising:
a first plurality of grains of hard material having a first average grain size;
at least a second plurality of grains of hard material having a second average grain size that is at least about thirty-three (33) times larger than the first average grain size, the first plurality of grains and the at least a second plurality of grains being interspersed and interbonded to form a polycrystalline hard material;
an interstitial material comprising at least one material selected from the group consisting of calcium carbonate, strontium carbonate, barium carbonate, and metal bicarbonates; and
an additional interstitial material comprising a catalyst material selected from the group consisting of iron, nickel, cobalt, and alloys thereof;
wherein the interstitial material is concentrated around the first plurality of grains of hard material.
2. The polycrystalline compact of claim 1 , wherein a ratio of the second average grain size to the first average grain size is between about 33:1 and about 40,000:1.
3. The polycrystalline compact of claim 1 , wherein the first average grain size is between about 1 nanometer (1 nm) and about one hundred fifty nanometers (150 nm).
4. The polycrystalline compact of claim 1 , wherein the second average grain size is between about five microns (5 μm) and about forty microns (40 μm).
5. The polycrystalline compact of claim 1 , wherein the first plurality of grains of hard material comprises between about one-half of one percent (0.5%) and about thirty percent (30%) by volume of the polycrystalline compact.
6. The polycrystalline compact of claim 1 , wherein the interstitial material comprises less than about ten percent (10%) by volume of the polycrystalline compact.
7. The polycrystalline compact of claim 1 , wherein the first plurality of grains comprises diamond.
8. The polycrystalline compact of claim 1 , wherein the first plurality of grains comprises cubic boron nitride.
9. An earth-boring tool, comprising
a body; and
at least one cutting element attached to the body, the at least one cutting element comprising a hard polycrystalline material consisting essentially of:
a plurality of grains of hard material, the grains comprising:
a first plurality of grains of hard material having a first average grain size;
at least a second plurality of grains of hard material having a second average grain size that is at least about thirty-three (33) times larger than the first average grain size, the first plurality of grains and the at least a second plurality of grains being interspersed and interbonded to form a polycrystalline hard material;
an interstitial material comprising at least one material selected from the group consisting of calcium carbonate, strontium carbonate, barium carbonate, and metal bicarbonates; and
an additional interstitial material comprising a catalyst material selected from the group consisting of iron, nickel, cobalt, and alloys thereof;
wherein the interstitial material is concentrated around the first plurality of grains of hard material.
10. The earth-boring tool of claim 9 , wherein a ratio of the second average grain size to the first average grain size is between about 33:1 and about 40,000:1.
11. The earth-boring tool of claim 9 , wherein the first plurality of grains comprises diamond.
12. The earth-boring tool of claim 9 , wherein the first plurality of grains comprises cubic boron nitride.
13. A particulate mixture for forming a polycrystalline compact, the particulate mixture consisting essentially of:
a plurality of grains of hard material, the grains comprising:
a first plurality of grains of hard material having a first average grain size and having a coating comprising at least one material selected from the group consisting of calcium carbonate, strontium carbonate, barium carbonate, and metal bicarbonates; and
a second plurality of grains of hard material having a second average grain size at least about thirty-three (33) times larger than the first average grain size, the second plurality of grains being interspersed with the first plurality of grains; and
a catalyst material selected from the group consisting of iron, nickel, cobalt, and alloys thereof;
wherein the coating is concentrated around the first plurality of grains of hard material and separates the first plurality of grains from the catalyst material;
wherein the first plurality of grains comprises between about one-half of one percent (0.5%) and about thirty percent (30%) by volume of the particulate mixture.
14. The particulate mixture of claim 13 , wherein the first average grain size is less than five hundred nanometers (500 nm).
15. The particulate mixture of claim 13 , wherein each of the first plurality of grains and the second plurality of grains comprises grains of diamond.
16. The particulate mixture of claim 13 , wherein each of the first plurality of grains and the second plurality of grains comprises grains of cubic boron nitride.
17. The polycrystalline compact of claim 1 , wherein the plurality of grains of hard material consists essentially of the first plurality of grains and the at least a second plurality of grains.