CA2348049C

CA2348049C - Toughness optimized insert for rock and hammer bits

Info

Publication number: CA2348049C
Application number: CA002348049A
Authority: CA
Inventors: Daniel J. Belnap; Nathan Roy Anderson; Michael Allen Siracki; Sujian Huang
Original assignee: Smith International Inc
Current assignee: Smith International Inc
Priority date: 2000-05-18
Filing date: 2001-05-17
Publication date: 2005-12-06
Anticipated expiration: 2021-05-17
Also published as: CA2348049A1; GB2362406B; GB0112111D0; GB2362406A

Abstract

An insert for a drill bit is disclosed which includes an exposed surface having a contact portion adapted to periodically contact earthen formation.
The contact portion includes a polycrystalline diamond material having a hardness in the range of about 2000 HV to about 3000 HV. In some embodiments, the polycrystalline diamond material includes a composite having a first phase material including polycrystalline diamond and a second phase material selected from the group of oxide particulates metal carbides, and metallic particulates, nitrides, and mixtures of thereof.

Description

TOU'GI~NESS OPTIMIZED xNSERT ~'(aR ROCS AND
HAMMER BX'~'S
Background of the Invention Field of the'lnvention [0001] The invention relates generally to cutting elements ("inserts") used on rock bits such as roller cone rock bits, hammer bits and drag bits. More specifically, the invention relates to optimi2,ing the toughness of an insert by lowering its hardness to increase the eB'ective drihing life of the insert for its particular dz~illing application.
Background Art [0002] Polycrystalline diamond ("PC17'~ enhanced inserts and tungsten carbide ("WC-Co") inserts are two commonly used inserts for roller cone rock bits and hammer bits. Roller cone rock bits include a bit body adapted to be coupled to a rotatable drill string and include at least one "cone" that is rotatably mounted to the bit body. The cone has a plurality of inserts pressed into it, The inserts contact with the formation during drilling. Hamnner bits are typically include a one piece body with having crown. The crown includes inserts pressed therein for being cyclically "hammered" and rotated against the earth formation being drilled.

The PCD layer on PCD enhanced inserts is extremely hard. As a result, the PCD layer has excellent wear resistance properties. While the actual hardness of the PCD layer varies for the inserts used in each of the foregoing bit types, each type of PCD has a common failure mode of chipping and spalling due to cyclical impact loading on the inserts during drilling. Conversely, the softer, tougher tungsten carbide inserts tend to fail by excessive wear and not by chipping and spalling.
Therefore a need exists for inserts for roller cone and hammer bits that are optimized for resisting both wear and impact as encountered during drilling.
According to one aspect of the present invention there is provided a rock bit, comprising: a body; at least one cutter rotatably mounted on the body; and at least one insert disposed in the at least one cutter, the at least one insert comprising an exposed surface having a contact portion thereon adapted to periodically contact earthen formation as the at least one cutter rotates, the contact portion comprising a polycrystalline diamond material, wherein the polycrystalline diamond material comprises a composite material comprising a first phase material comprising polycrystalline diamond, and at least 10 percent by volume of a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the polycrystalline diamond having a hardness in the range of about 2000 Vickers Hardness Units to about 3000 Vickers Hardness Units.
According to a further aspect of the present invention there is provided an insert for a drill bit comprising an exposed surface having a contact portion thereon adapted to contact earthen formation, the contact portion comprising a polycrystalline diamond material, wherein the polycrystalline diamond material comprises a composite material comprising a first phase material comprising polycrystalline diamond, and at least 10 percent by volume of a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the polycrystalline diamond having a hardness in a range of about 2000 Vickers Hardness Units to about 3000 Vickers Hardness Units.
According to another aspect of the present invention there is provided a rock bit, comprising: a body; at least one cutter rotatably mounted on the body;
and at least one insert disposed in the at least one cutter, the at least one insert comprising an exposed surface having a contact portion thereon adapted to periodically contact earthen formation as the at least one cutter rotates, the contact portion comprising a polycrystalline diamond material, the polycrystalline diamond material comprising a composite material, the composite material comprising a first phase material comprising polycrystalline diamond, and a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the second phase material being between about 20 and 50 percent by volume of the composite material.
According to a still further aspect of the present invention there is provided a .
hammer bit, comprising: a body with a shank portion for being received in a hammer assembly and a head portion opposite thereto for impacting rock formation; and at least one insert mounted on the head portion, the at least one insert comprising an exposed surface having a contact portion thereon, the contact portion comprising a polycrystalline diamond material, the polycrystalline diamond material comprising a composite material, the composite material comprising a first phase material comprising polycrystalline diamond, and a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the second phase material being between about: 20 and SO
percent by volume of the composite material.
According to another aspect of the present invention there is provided an insert for a drill bit comprising an exposed surface having a contact portion thereon adapted to contact earthen formation, the contact portion comprising a polycrystalline 2a diamond material, the polycrystalline diamond material comprising a composite material, the composite material comprising a first phase material comprising polycrystalline diamond, and a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the second phase material being between about 20 and SO percent by volume of the composite material.
One aspect of the invention is an insert for a drill bit is disclosed which includes an exposed surface having a contact portion adapted to periodically contact earthen formation. The contact portion includes a polycrystalline diamond material having a hardness in the range of about 2000 HV to about 3000 H'V.
In some embodiments, the insert is attached to a roller cone on a roller cone bit. Xn some embodiments, the insert is attached to a crown on a hammer bit.
In some ernbodinrents, the polycrystalline diamond material includes a composite having a first phase material including polycrystalline diamond and a second phase material selected from the group of oxide particulates metal carbides, and metallic paarticulates, nitrides, an,d mixtures of thereof.
Another aspect of the invention is a lock bit including a body, at least one cutter rotatably mounted on the body, and at least one insert disposed in the at least one cutter. The at least one insert has an Exposed sw~''ace having a contact portion thereon adapted to periodically contact earthen formation as the cutter rotates. The contact portion comprises a polycrystalline diamond material, which itself comprises a composite material. The composite material comprises a fwst phase material comprising polycrystalline diamond, and a second phase wmaterial 2b selected from the group of oxide particulates metal carbides, and metallic particulates, nitrides, and mixtures of thereof.
[0008] In some embodiments, the polycrystalline diamond material has a hardness in a range of about 2000 to 3000 Vickers Tlardness Units (HV).
[0009] Other aspects and advantages of the invention will be apparent from the accompanying drawings, description and appended claims.
Brief Aescription of the Drawings [00x0] Figure 1 is a conceptual graph of wear resistance versus hardness of a PCD
insert;
[0011] Figure 2 is a picture of a microstructure having dense intercrystalline bonding in a PCD material;
[0012] Figure 3 is a pictuxe of a microstructure having less dense intererystalline bonding in a PCD material;
[0013] Figure 4 is a side view of a roller cone rock bxt;
[0014] Figure s is a cross-sectional view of one preferred embodiment of an insert according to the present invention;
[0015] Figure 6 is a cross-sectional view of an alternative embodiment of an insert according to the present invention;
[0016] Figure 7 is a cross-sectional view of another alternative embodiment of an insert according to the present invention;
[0017] k'igure $ is a side view of a hammer bit; and [0018] Figure 8A is a cross-sectional vices of one embodiment of azt~ insert preferred for use in a hammer bit.

Detailed Description [0019] Various embodiments of the invention provide a toughness-optimized PCD
surface for inserts used an drill bits_ It is known in the art that hardness of a PCD
surface on an insert, or PCl~ material used to make the insert, generally correlates with its .wear resistance. It is also known in, the art that the toughness of the PCD
layer, ar material used to make the insert, generally correlates to its impact resistance. Generally speaking, the harder the material is the less toughness it has, and vice versa. This trade off between hardness and toughness extends to wear resistance arid impact resistance. While 'wear resistance is an important property of drill bit inserts, the present invention optimizes the trade off between wear resistance and impact resistance to provide an insert better suited for its bit type and forn~.ation to be drilled.
(0020) Morc spccihcally, it has been determined through analysis of worn out ("dull") roller cone bits that many PCD-enhanced inserts have more wear resistance than rnay be necessary for their respective drilling application.
This conclusion is based on the failure mode of the inserts being chipping or spalling, which is characteristic o~ impact failure. Impact failure is indicative of insufficient toughness of the insert. Toughness as previously explained, is generally inversely related to the hardness and wear resistance of the particular insert. Thus, the wear resistance of typical PCD enl'tanccd inserts can be reduced, while a corresponding gain in impact resistance andlor fatigue life can be expected to provide a disproportirnnate increase in the overall insert life during actual drxhing use. 'That is, even though the wear resistance of the insert may be reduced, the effective life of the insert is increased due to the postponement or elimination of the impact failure mode. For purposes of simplicity, the term "impact resistance" will be used generically also to include fatigue failure. Fatigue failure also increases as the hardness of PCD increases.

(0021] >~igurc 1 shows this concept in graphic form. The y-axis on the graph of Figure 1 generally represents insert life which can be empirically evaluated from analysis of dull bits. The x-axis in the graph of Figure 1 represents the hardness of the PCD surface of PCD-enhanced inserts. 'Phil hardness can be determined by standard hardness testing techniques. "Insert life" represents the approximate time an insert drills through earth formations until it becomes excessively worn.
Wear can result from either abrasive erosion of the inset, or chipping and spalling caused by cyclical impact loading. Excessive wear renders the insert ineffective fox drilling. This condition can be indicated by a shazp decrease in the rate of penetration ("ROP") of the bit during drilling, and is confirmed by dull bit evaluation. Additionally, there may be at some point simulation methods to predict insert life when the insert is used to drill through selected fornxations.
[0022] It can be observed at point 1 on the graph in Figure 1 that a low hardness provides relatively low insert life. Increasing hardness thexeaftex, up to a point, generally increases insert life. The predominant insert failuxe mode between points 1 and 2 tends to be excessive wear of the insert. I-Iowcvcr, there appears to be a point (shown at point 2) beyond which insert life begins to decrease despite the increase in hardness of the insert material. An insert with a hardness at point 3 ' may actually have a shorter life than an insert at paint 2, because impact failure rnay cause the insert to fail prematurely. An insert at point 3 is more wear resistant than an insert at point 2, but at hardness values higher than at point ~, impact failure becomes the prevailing failure mode. 1''he invention prozzdes an xt~sert which has a hardness shown at paint 2 so that the hardness and toughness art optimally selected to withstand both impact fatigue and wear to achieve the longest insert life for the particular insert application.
(0023] For comparison purposes, a typical tungsten carbide insert life curve has been included on Figure 1, shown at 4, along with point 3 representing conventional PCD. It can be observed that the higher hardness PCD, at point 3, can be expected to have a longer insert life than tungsten carbide, but there still exists an area of improvement for insert life, as shown in the hatched area S.
The present invention provides an insert that has a hardness that falls between point 3 and 4 on the hardness scale so that the insert life is maximized for a particular drilling application. lzt other words, the inserts of the present invention are substantially toughness optimized, as represented under point 2 in Figure I .
j0024] The hardness value of points 2 and 3 on the curve of Figure 1 depends on the type of drill bit, the location of the insert on the drill bit, the type of earth formation to be drilled, and the drilling parameters such as weight on bit and rotary speed (RPM}. For example, toughness optimized inserts used in hammer bits will generally have a higher hardness than toughness optimized inserts used in roller cone bits. However, the one thing that will be consistent is that each of these toughness optimized inserts will have a Lower hardness than a corresponding conventional insert for the same drill bit and application. That is, each ixtsert will move into the hatched area in Figure I to achieve a higher insert life for the particular application.
j0025] PCD is a well known and commonly used material for drilling inserts.
PCD can have a variety of geometries when used on inserts used in drill bits, for example, thin layers or thick masses disposed on substrates, a variety of exterior shapes for contacting the formation, a variety of non-planar interfaces with a substrate, or the entire insert being PCD. ~'Cp may have a variety of additional materials combined with the PCD, for example, cobalt and tungsten carbide, that are added for puzposes urt~related to the present invention. For example, cobalt up to about I O % by volume is typically used to aid the ~si~xatering process.
U.S. Patent 3Vo. 5,370,195 discloses an outer PCb layez including carbides or carbonitrides in ~a range of up to 8% by volume; however, this percentage is considered xz~sufficient to increase the irr~pact resistance to the extent contemplated by the present invention.

[0026] One constant aspect of the definition of PCD is the use of a high temperature/high pressure ("HT/HP") process for sintering "green" PCD to create intercrystalline bonding between diamond crystals. "Sintering" as used herein refers to a HTIHP process fvr pressing green PCD. HT/HP processes are well known in the art. For exanttple, U.S. patent No. 5,~70,1.~5 discloses a HT~HP
process. U.S. Patent No. 4,525,17$ discloses a typical use of diamond crystals vcrith cobalt powder as a binder that is formed inn a green state, and then is pressed through a HT/HP press to yield a PCD with strong intercrystalline bonding.
PCD, by its very name, has intercrystalline bonding between diamond crystals. The HTIHP process only needs to provide sufficient time, ternpexature and pressure to ct'eate this intererystalline bonding. This is so even when other materials such as tungsten carbide are pressed along with the green diamond crystals., In some cases there may be so much additional material, such as tungsten carbide or cobalt as explained earlier, that appreciable intercrystalline bonding is effectively prevented during the sizttexiztg process. Such a material is not within the definition of the term PCD where appreciable intercry5talliate bonding has not occurred. 4zt tl-~e other hand, intercrystalline bonding is present if the additional material has merely lessened the degree of intercrystalline contact between adjacent diamond crystals.
For example, diamond crystals mixed with any second material (second phase) such that the diamond is less than about 20% by volume generally would not be expected to have appreciable iritercrystalline bonding. However, the true measure of whether there is intexcrystalline bonding is by examination of the speci~xc micro structure of any composition of diamond and additional materials.
[0027] The degree of intercrystalline bonding correlates with the hardness of the PCD. Very dense intercrystalline bonding results in the highest hardness, as shown in Figure 2. More vcridely dispersed intercrystalline bonding results in a lower hardness, as shown in Figure 3. More widely disposed intercrystalline bonding~typically results in higher toughness and impact resistance.

[0028] Referring to Figure 4, a roller cone rack bit 10 according to the preferred roller cone bit embodiment of the present invention is shown disposed in a borehole 11. The bit 10 has a body 12 with legs I4 extending generally downward, and a threaded pin end 15 opposite thereto for attaehrnent to a drill string (not shown). Jouxnal shafts 16 are cantilevered from legs 14. Rolling cutters (or roller cones) I8 are rotatably mounted on journal shafts 16. Each cutter 18 has a plurality of inserts 20 mounted thereon. As the body 10 is rotated by rotation of the drill string (not shown), the cutters 18 rotate over the borehole bottorrt 22 and maintain the gage of the borehole by rotating against a portion of the borehole sidewall 24. As the cutter 18 rotates, individual inserts are rotated into contact with the formation and then out of contact with the formation. As a result, the inserts undergo cyclical loading which can contribute to fatigue failure.
Inserts 26 are called "gage" inserts because they contact, at Ieast partially, the sidewall 24 to maintain the gage of the borehole 1 x . All of the inserts, and particularly gage inserts 26, undergo repeated impact loading as they arc rotated into and out of contact with the earth formation.
[0029] Referring to Figure 5, a cross-section of one embodiment of an insert according to the present invention is shovsrn. The insert 2$ may be used as any one of the inserts 20 but has particular applicafiion as a gage insert 26. Insert 28 has a substrate 30 with a grip portion 32 and an extension portion 34. The grip portion 34 is sized for a press 1~xt within sockets formed in rolling cutters 1$. An outer layer 36 is located on the extension portion 34. Outer layer 36 has an inner surface 3$ and a contact surface 40 opposite thereto for contacting the borehole.
The embodiment of Figura 5 shows the outer layer 36 as covering the entire extension portion 34; however, it should be understood that the outer layer 36 may only cover a part of the extension portion 34. Additionally, there may be other layers interposed between the outer layer 36 and the substrate 32. See, fox example, transition layers as disclosed in U, S. Patent 'hTa. 4,64,9 x 8.
s [0030] The outer layer 3b comprises a composite PCD material. Preferably for a roller cone bit application, the contact surface 40~ of the outer layer 3G has a hardness of between about 2000 to 3000 Vickers I~ardx~ess Units (HV). This hardness provides a resulting increase in impact resistance that is beneficial for inserts used in roller cone drill bits, while not significantly sacrificing wear resistance. In some embodiments, the PCD hazdness is within a range of about 2000 to 2500 HV. In other embodiments, the PCD hardness is within a range of about 2500 to 3000 HV.
[0031] An alternative embodiment of an insert is shown in Figure b. The insert 2$A in the embodiment of Figure 6 is made substantially entirely from a composite PCD material made as previously described herein and having a hardness in a range of about 2000 to 3000 HV. In some embodiments, the PCD
hardness is within a range of about 2000 to 2500 HV. In other embodiments, the composite PCI? material hardness is within a range of about 2500 to 3000 HV.
(0032] Yet another tmbodirnent of an insert is shown in Figure 7 at 28B. The insert 2$B includes a generally cylindrical substrate 32A and a generally convex-shaped contact surface 36A disposed at ane end of the substrate. The contact surface is placed into recurrent contact with the earth formation as the drill bit is operated. The contact surface 36A is formed from composite PCD material made as explained herein previously, and preferably has a hardness in a range of about 2000 to 3000 HV. In sonr~e embodiments, the composite f CD material hardness is within a range of about 2000 to 2500 HV. In other embodiments, the composite PCD material hardness is within a range of about 2500 to 3000 HV.
[0033] A suitable technique for measuring the hardness of the composite PCD
material used in an insert according to the invention is descn'bed as follows.
A
sectioned insert is lapped with sequentially-decreasing grit lapping compound down to 1-3 micron diamond grit. This lapped surface is then subjected to contact with a high-speed, resin-bonded diamond wheel for final polishing. T-Iardness is typically measured at a location on the polished PCD surface, preferably near the contact surface. The hardness testing procedure uses a Vickers indenter with a 500 gram toad on a conventional microhardztess testing apparatus. The indenter loading and measurement of the resulting hardness impressions are perfon~.ed using procedures known in the art.
[0034] In preferred embodiments of a composite PCD material made according to the invention, an additional material, referred to as a "second phase"
material, is added to diamond crystals to reduce the intercrystalline bonding which decreases the hardness and thereby increases the toughness and impact resistance.
Together, the polycrystalline diamond and the second phase material form a composite material that undergoes HTIHP processing to form a composite PCD material.
One preferred second phase material is tungsten carbide-cobalt (WC-Co).
However, the second phase material could be any covalent, ionic, or metallically bonded substance which sufficiently interferes with intercrystalline bonding of the diamond during the HT/HP process. Examples of such substances include:
particulate oxides, for example, aluminum oxide anal zirconium oxide; metal such as of tungsten, vanadium, titanium; and metallic particulates such as cobalt, nickel, and iron; nitrides; and mixtures of any or all of the foregoing materials. In some embodiments, the second phase material makes up about 10 to 60 percent by volume of the composite material formed into PCD by the HP~'~' process. More preferably, the second phase material forms 20 to 50 percent by volume of the composite material.
[0035] One measure used to determine the toughness of a PCD-enhanced insert is an impact test. An insert is placed in a rigid fixture, and a selected weight is dropped from predetermined heights. The PCD surface is then observed for chipping or other signs of impact damage. The maximum height, termed "drop height", that an insert can withstand the drop test is a measure of the impact resistance, and thus toughness, of the insert.
EXAN~'~E
[0036] In an example of a composite PCD material made according to the invention, 60% by volume of diamond and 40% by volume of precemented tungsten carbide powder were combined and sintered. The average diamond grain size was about 6 microns aztd tha average prccemented t<mgstcn carbide grain size vcras about 20 microns. The resulting haxdness of the composite PCD material was 2300 i-fV. The relative improvement in impact resistance as compared to conventional PCD was about 100%, with the drop height increasing firorn about inches for a conventional PCD enhanced insert to about 97 inches for an composite PCD enhanced insert according to the example.
[0037] Figuxes 8 and 8A illustrate azt ernbodixx~,ez~t of a harirrrrzex bit having inserts made according to the invention. The hammer bit IO has a body I 1z vcrith a head 114 at one end thereof ~'he body 112 is received in a hammer 118, and the hammer 118 moves the head 114 against the formation to fracture the formation.
Inserts 120 are xzxounted in the head 114. The inserts 120 are preferably semi-round top (Sl~'f) inserts With a substrate I30 and a grip portion 132. The grip portion 132 is pressed into the head 114 and an extension poxfiion 134 extends from the head 114. An outer Iayer 136 is formed from composite PCD material, made as previously explained, with inner surface 138 toward substrate 130 and contact surface I40 opposite thereto fox impacting borehole bottom 122 andlor sidewall I24. For a hammer bit insert 120, it is preferred that the hardness of contact surface 140 be between about 2000 and 3000 HV. The hardness of the composite PCD layer (outer Iayer 136) is preferably made as discussed above with respect to roller cone bit insert 20.

[0038] Although the present invention has been described with respect to a limited number of embadiments, various changes, substitutions and modifications may be suggested to one skilled in the art and it is intended that the present invention encompass such changes, substitutions and modifications as fall within the scope of the appended claims. Accordingly, the scope o~ the invention is to be lirnited only by the appended claims.

Claims

1. A rock bit, comprising:

a body;
at least one cutter rotatably mounted on the body; and at least one insert disposed in the at least one cutter, the at least one insert comprising an exposed surface having a contact portion thereon adapted to periodically contact earthen formation as the at least one cutter rotates, the contact portion comprising a polycrystalline diamond material, wherein the polycrystalline diamond material comprises a composite material comprising a first phase material comprising polycrystalline diamond, and at least 10 percent by volume of a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the polycrystalline diamond having a hardness in the range of about 2000 Vickers Hardness Units to about 3000 Vickers Hardness Units.

2. The bit of claim 1 wherein the hardness of the polycrystalline diamond is in the range of about 2000 Vickers Hardness Units to about 2500 Vickers Hardness Units.

3. The bit of claim 1 wherein the hardness of the polycrystalline diamond is in the range of about 2500 Vickers Hardness Units to about 3000 Vickers Hardness Units.

4. The bit of any one of claims 1 to 3 wherein the second phase material is between about 10 and 60 percent by volume of the composite material.

5. The bit of any one of claims 1 to 3 wherein the second phase material is between about 20 and 50 percent by volume of the composite material.

6. The rock bit of any one of claims 1 to 5 wherein the at least one insert comprises a substrate material having the polycrystalline diamond material disposed on an outer surface thereof.

7. The rock bit of claim 6 further comprising at least one additional layer interposed between the polycrystalline diamond material and the substrate material.

8. The rock bit of any one of claims 1 to 7 wherein the contact portion comprises at least a portion of a convex surface formed on the insert

9. An insert for a drill bit comprising an exposed surface having a contact portion thereon adapted to contact earthen formation, the contact portion comprising a polycrystalline diamond material, wherein the polycrystalline diamond material comprises a composite material comprising a first phase material comprising polycrystalline diamond, and at least 10 percent by volume of a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the polycrystalline diamond having a hardness in a range of about 2000 Vickers Hardness Units to about 3000 Vickers Hardness Units.

10. The insert of claim 9 wherein the hardness of the polycrystalline diamond is within a range of about 2000 Vickers Hardness Units to about 2500 Vickers Hardness Units.

11. The insert of claim 9 wherein the hardness of the polycrystalline diamond is within a range of about 2500 Vickers Hardness Units to about 3000 Vickers Hardness Units.

12. The insert of any one of claims 9 to 11 wherein the second phase material is between about 10 and 60 percent by volume of the composite polycrystalline diamond material.

13. The insert of any one of claims 9 to 11 wherein the second phase material is between about 20 and 50 percent by volume of the composite polycrystalline diamond material.

14. The insert of any one of claims 9 to 13 wherein the insert comprises a substrate material having the polycrystalline diamond material disposed on an outer surface thereof.

15. The insert of claim 14 further comprising at least one additional layer interposed between the composite polycrystalline diamond material and the substrate material.

16. The insert of any one of claims 9 to 15 wherein the contact portion comprises at least a portion of a convex surface formed on the insert.

17. The insert of any one of claims 9 to 16 wherein the insert is disposed in a crown of a hammer bit.

18. The insert of any one of claims 9 to 16 wherein the insert is disposed in a roller cone of a roller cone bit.

19. A rock bit, comprising:
a body;
at least one cutter rotatably mounted on the body; and at least one insert disposed in the at least one cutter, the at least one insert comprising an exposed surface having a contact portion thereon adapted to periodically contact earthen formation as the at least one cutter rotates, the contact portion comprising a polycrystalline diamond material, the polycrystalline diamond material comprising a composite material, the composite material comprising a first phase material comprising polycrystalline diamond, and a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the second phase material being between about 20 and 50 percent by volume of the composite material.

20. The hammer bit of claim 19 wherein a hardness of the polycrystalline diamond is in the range of about 2000 Vickers Hardness Units to about 3000 Vickers Hardness Units.

21. The rock bit of claim 20 wherein a hardness of the polycrystalline diamond is in the range of about 2500 Vickers Hardness Units to about 3000 Vickers Hardness Units.

22. The rock bit of claim 20 wherein a hardness of the polycrystalline diamond is in the range of about 2000 Vickers Hardness Units to about 2500 Vickers Hardness Units.

23. The rock bit of any one of claims 19 to 22 wherein the insert is formed substantially entirely of the polycrystalline diamond material.

24. A hammer bit, comprising:
a body with a shank portion for being received in a hammer assembly and a head portion opposite thereto for impacting rock formation; and at least one insert mounted on the head portion, the at least one insert comprising an exposed surface having a contact portion thereon, the contact portion comprising a polycrystalline diamond material, the polycrystalline diamond material comprising a composite material, the composite material comprising a first phase material comprising polycrystalline diamond, and a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the second phase material being between about 20 and 50 percent by volume of the composite material.

25. The insert of claim 24 wherein a hardness of the polycrystalline diamond is in the range of about 2000 Vickers Hardness Units to about 3000 Vickers Hardness Units.

26. The hammer bit of claim 25 wherein a hardness of the polycrystalline diamond is in the range of about 2500 Vickers Hardness Units to about 3000 Vickers Hardness Units.

27. The hammer bit of claim 25 wherein a hardness of the polycrystalline diamond is in the range of about 2000 Vickers Hardness Units to about 2500 Vickers Hardness Units.

28. An insert for a drill bit comprising an exposed surface having a contact portion thereon adapted to contact earthen formation, the contact portion comprising a polycrystalline diamond material, the polycrystalline diamond material comprising a composite material, the composite material comprising a first phase material comprising polycrystalline diamond, and a second phase material selected from the group of oxide particulates, metal carbides, metallic particulates, nitrides, and mixtures thereof, the second phase material being between about 20 and 50 percent by volume of the composite material.

29. The insert of claim 28 wherein a hardness of the polycrystalline diamond is in the range of about 2000 Vickers Hardness Units to about 3000 Vickers Hardness Units.

30. The insert of claim 29 wherein a hardness of the polycrystalline diamond is in the range of about 2500 Vickers Hardness Units to about 3000 Vickers Hardness Units.

31. The insert of claim 29 wherein a hardness of the polycrystalline diamond is in the range of about 2000 Vickers Hardness Units to about 2500 Vickers Hardness Units.