DIAMOND DRILL BIT AND METHOD OF PRODUCING A DIAMOND DRILL BIT

Abstract

The diamond drill bit comprises a steel powder comprising iron in a non-zero proportion of up to 99.6% iron and carbon in a proportion between 0.03% and 2.14%, coated diamonds impregnated in the steel powder, and a metallic infiltrant alloy comprising copper and one of tin, silver and both tin and silver; wherein the diamond drill bit is produced by an infiltration process that comprises providing the steel powder to form the matrix; dispersing coated diamonds in the steel powder; compressing the matrix comprising the steel powder and the coated diamond at a cold-compression temperature; after the compressing, adding to the matrix an infiltrant alloy comprising copper and one of tin and silver; and heating the mixture of steel powder, coated diamonds and infiltrant alloy at a fusion temperature allowing the infiltrant alloy to melt, wherein the infiltrant alloy infiltrates the matrix and binds it.

Claims

1. A diamond drill bit comprising a steel powder comprising iron in a non-zero proportion of up to 99.6% and carbon in a proportion between 0.03% and 2.14%, coated diamonds impregnated in said steel powder, and a metallic infiltrant alloy comprising copper and one of tin, silver and both tin and silver; wherein said diamond drill bit is produced by an infiltration process.

2. A diamond drill bit as defined in claim 1, wherein said steel powder further comprises one or more of the following metals: manganese, silicon, phosphorus, sulfur, copper, nickel, chromium, aluminium, titanium, boron, molybdenum and vanadium.

3. A diamond Drill bit as defined in claim 1, wherein said steel powder further comprises tungsten.

4. A diamond drill bit as defined in claim 1, wherein said infiltrant alloy comprises 50-92% copper and 2-50% silver.

5. A diamond drill bit as defined in claim 1, wherein said infiltrant alloy comprises between 75-95% copper and 5-25% tin.

6. A diamond drill bit as defined in claim 1, wherein said infiltrant alloy further comprises zinc.

7. A diamond drill bit as defined in claim 1, wherein said infiltrant alloy further comprises bismuth.

8. A diamond drill bit as defined in claim 1, wherein said steel powder comprises iron particles of a size between 1 and 300 microns.

9. A method of producing a diamond drill bit as defined in claim 1 by an infiltration process, comprising: providing the steel powder to form a matrix; dispersing the coated diamonds in said steel powder; compressing said matrix comprising said steel powder and said coated diamond at a cold-compression temperature; after the step of compressing said matrix, adding to said matrix an infiltrant alloy comprising copper and one of tin and silver to form a drill bit mixture; and heating the drill bit mixture at or above a fusion temperature of said infiltrant alloy, for allowing said infiltrant alloy to melt, wherein said infiltrant alloy infiltrates said matrix and binds it.

10. The method as defined in claim 9, wherein said infiltrant alloy comprises 50-92% copper and 2-50% silver.

11. The method as defined in claim 9, wherein said infiltrant alloy comprises between 75-95% copper and 5-25% tin.

12. The method as defined in claim 9, wherein the step of providing the steel powder comprises providing a ferrous-based powder and graphite that comprises carbon, and wherein before the step of heating the mixture at or above a fusion temperature of said infiltrant alloy, said method further comprising the step of heating said drill bit mixture at or above a diffusion temperature of the carbon in the iron but below the fusion temperature of said infiltrant alloy for allowing the carbon to migrate into said iron.

13. The method as defined in claim 1, wherein said steel powder further comprises one or more of the following metals: manganese, silicon, phosphorus, sulfur, copper, nickel, chromium, aluminium, titanium, boron, molybdenum and vanadium.

14. The method as defined in claim 1, wherein said steel powder further comprises tungsten.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In the annexed drawings:

[0038] FIG. 1 is a perspective view of a diamond drill bit according to the present invention;

[0039] FIG. 2 is a table showing different steel compositions that can be used for providing the steel powder composing the matrix of the drill bit; and

[0040] FIG. 3 is a graphic showing the results of three-point flexion tests for three different drill bit matrix samples having respective compositions.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] According to the present invention, a diamond drill bit has been developed including a matrix composition that offers lower production costs while yielding similar and comparable mechanical properties than those of conventional prior art matrixes that include tungsten powder admixed with a metallic infiltrant and diamonds.

[0042] The diamond drill bit of the present invention has been developed comprising a matrix impregnated with diamonds and infiltrated with a metallic alloy according to an infiltration process, with the matrix comprising steel powder.

[0043] More particularly, the matrix comprises a steel powder having a nonzero proportion of iron of up to 99.6% iron. The steel powder also comprises a minimum of 0.03% Carbon and up to 2.14% Carbon. FIG. 2 shows a number of steel compositions that have been used to produce the steel powder used in the diamond drill bit matrix. The matrix composition can comprise, for example, about 70 grams of steel powder for 200 grams of metallic alloy, plus about 14 grams of diamonds.

[0044] The dimension of the steel powder particles that will compose the steel powder will influence the resistance to wear of the matrix. Steel powder particles size between 1 and 300 microns have been tested to be particularly advantageous. So depending on the type of ground being bored through and the desired rate at which the matrix should wear out, different sizes of steel powder particles can be used.

[0045] According to the present invention, the metallic infiltrant alloy can be either a copper-silver alloy or a copper-tin alloy, or a copper-silver-tin alloy.

[0046] In the embodiment where it is a copper-silver alloy, the composition of the infiltrant can be 50-92% copper and 2-50% silver. In an embodiment where a copper-tin alloy is employed, the composition of the infiltrant can be between 75-95% copper and 5-25% tin.

[0047] Nickel has been used as an optional additive in a copper-silver infiltrant to provide advantageous results. Nickel increases the wettability of the steel powder particles, making the alloy more fluid.

[0048] The following exemplary matrix compositions have been successfully produced: [0049] 1) 60% Cu-40% Ag [0050] 2) 74% Cu-18% Ag-8% Ni [0051] 3) 73% Cu-25% Ag-2% Ni [0052] 4) 76.8% Cu-19.2% Ag-4% Ni [0053] 5) 78.4% Cu-19.6% Ag-2% Ni [0054] 6) 80% Cu-15% Ag-5% Ni [0055] 7) 58% Cu-37% Ni-5% Ag [0056] 8) 84.5% Cu-14% Sn-1.5% Zn [0057] 9) 83% Cu-14% Sn-1.5% Zn-1.5% Bi [0058] 10) 84% Cu-14% Sn-1.5% Zn-0.5% Bi

[0059] In one embodiment, the infiltrant alloy comprises zinc in addition to copper and tin. The addition of zinc helps increase the structural harness of the bronze matrix composition.

[0060] In one embodiment, the alloy further comprises bismuth in addition to the copper, tin and zinc combination. Bismuth has been found to decrease resistance to wear, so it is advantageously used in circumstances where a higher wear rate of the matrix is desired.

[0061] The drill bit composition described in the present invention has been tested and found to provide mechanical properties that are equivalent or similar to those of the prior art compositions, albeit at a cheaper price.

[0062] FIG. 3 indeed shows the results of three-point flexion tests for three different drill bit matrix samples having respective compositions. For all three drill bit matrix compositions, a copper-silver-nickel alloy was used. Curve 50 is obtained from a matrix comprising tungsten powder per the prior art. Curve 52 is obtained from a matrix comprising steel powder according to the present invention. Curve 54 is obtained from a matrix comprising pure iron powder.

[0063] It can be seen from the results of FIG. 3 that the behavior of the steel powder matrix shown in curve 52 is very similar to that of the tungsten powder reference matrix 50. The pure iron powder has however shown to be too ductile, and furthermore pure iron powder-based matrixes have shown significant wear compared to steel powder matrixes. As also noted above, pure iron matrixes have shown to produce tools that deform during use under friction-induced heat, which is undesirable.

[0064] It can consequently be seen from the FIG. 3 graphic that pure iron powder matrixes are not desirable, whereas steel powder matrixes formed by infiltration process provide similar mechanical properties than that of tungsten powder matrixes. This was a surprising and unexpected result, and leads to the conclusion that steel matrixes can be used to produce a diamond drill bit in an infiltration process to obtain diamond drill bits that have comparable mechanical properties albeit at a much lower price. It is understood that diamond drill bits produced by infiltration process do not have the same mechanical properties at that of the diamond drill bits made with other production processes, such as a sintering process; and this is a feature, not a drawback, as it is known as noted in the Background of the Invention section to use diamond drill bits with different mechanical properties depending on the type of ground being drilled. The diamond drill bit of the present invention is produced with an infiltration process specifically, and it is not intended to compare, nor will it compare, to diamond drill bits produced with other processes such as a sintering process.

[0065] It is possible to use sealed kiln chambers wherein hydrogen or another inert gas is injected to deoxidize the alloy and promote the infiltration.

[0066] In the present specification, reference to compositions comprising percentages of certain elements, refers to percentages in mass.

[0067] The method of producing a diamond drill bit per the invention by an infiltration process consequently notably comprises providing the steel powder to form the matrix. It is noted that while the steel powder comprises a nonzero proportion of iron, otherwise it would not be characterized as steel.

[0068] It is also noted that a certain proportion of steel can be replaced by tungsten. While this is not necessarily desirable on a cost-effectiveness basis, it would still yield acceptable results. Replacing tungsten by steel is the purpose of the invention to obtain a more cost-effective drill bit, but if this is done only in a certain proportion, then the savings are consequently proportional.

[0069] The steel powder comprises a maximum of 99.6% iron. It has been determined that beyond this proportion, the diamond drill bit would become too ductile, and would be prone to deforming under use. In fact, it would then start to behave more like the pure iron sample shown at 54 than the steel sample shown at 52 in FIG. 3.

[0070] The steel powder also comprises at least 0.03% carbon. This minimum is required for the steel to acquire the necessary hardness, and not be too ductile, for the intended purpose of being used as a matrix for a diamond drill bit in an infiltration process. Carbon concentration should not go beyond 2.14% however because beyond that point cast iron will be formed instead of steel.

[0071] Other metals can be included in the matrix composition, for example one or more of the following metals: manganese, silicon, phosphorus, sulfur, copper, nickel, chromium, aluminium, titanium, boron, molybdenum, vanadium, tungsten, and any other element that is known to be part of certain steels.

[0072] The use of these metals, and others, to form steel with the iron and carbon is known in the art, and will be obvious for a metallurgist. It is further noted that the use of steel implicitly means that some of these metals can be used. In fact, if the upper threshold of 99.6% iron and the lower threshold of 0.03% carbon is used, then one or more other metals, including the above-mentioned metals or other metals, must be used.

[0073] However, it is contemplated that the steel could be formed of only iron and carbon: then, the minimum proportion of carbon would have to be 0.4%, since the maximum portion of iron is 99.6%.

[0074] The method includes the step of dispersing coated diamonds in the steel powder. This is known in the industry of producing diamond drill bits, and diamonds of known dimensions and coated with known compounds can be used.

[0075] The method also comprises compressing the matrix comprising the steel powder and the coated diamond at a cold-compression temperature. This cold-compression temperature can be, for example, at room temperature, or any other suitable temperature that will be obvious for someone skilled in the art.

[0076] After the compressing, the method comprises adding to the matrix an infiltrant alloy comprising copper and one of tin and silver, or both, as noted above, with possible additional metals as further noted above.

[0077] The method also comprises heating the mixture of steel powder, coated diamonds and infiltrant alloy at a fusion temperature or more, for allowing the infiltrant alloy to melt, wherein the infiltrant alloy infiltrates the matrix and binds it. The fusion temperature will of course depend on the infiltrant being used. The fusion temperature of some infiltrant alloys is for example 1000 C.: in this exemplary case, the step of heating would then occur at 1000 C. or more.

[0078] The steel powder can be provided from fully formed steel, or it can be provided with the iron and carbon particles independently of one another to then produce the steel during the infiltration process. Carbon is then provided in the form of graphite, while the iron can be provided in the form of a ferrous-based powder that includes iron and, optionally, other metals as noted above. The method of the invention would then include, before the step of heating the mixture at the fusion temperature or more, the step of heating the mixture at a diffusion temperature that is at least equal to a diffusion temperature of the carbon in the iron but inferior to the fusion temperature of the infiltrant alloy for allowing the carbon to migrate into the iron to form steel particles.