Wear enhancement of HDD drill string components

Abstract

A hard facing is preferably accomplished with laser clad beads applied to horizontal directional drilling (HDD) component(s). These components may be subject to recirculating fluid regions associated to stepped geometries along a drill string, including various drill string coupling members. For example, laser cladding can be applied to a step region of the sonar housing and starter rod. A method applies a hard face coating such as laser cladding or other suitable hard facing in areas of tight geometric tolerances.

Claims

1. A horizontal directional drilling (HDD) component for use in a drill string comprising two or more mechanically fastened members that provide a diametrically reduced stepped geometry along a direction of drilling, the horizontal directional drilling (HDD) component comprising: a drill string component including a selective hard facing arranged to reduce accelerated wear proximate a region of the diametrically reduced stepped geometry that is at a joint location which creates a step when the drill string component is arranged in overlapping relation with another of the mechanically fastened members such that the drill string component has a predetermined recirculation zone region with the selective hard facing applied along the predetermined recirculation zone region, the selective hard facing comprising a first discrete region applied on only one drill string component so as not to join to any other drill strip component through the selective hard facing.

2. The horizontal directional drilling (HDD) component of claim 1 wherein the drill string component is a starter rod.

3. The horizontal directional drilling (HDD) component of claim 2 wherein the starter rod utilizes a polygonal spline on the outer surface and internal thread region on the inner diameter to affectively lock it to the adjacent component.

4. The horizontal directional drilling (HDD) component of claim 2 wherein the starter rod has an outer diameter between 1 and 6 inches.

5. The horizontal directional drilling (HDD) component of claim 1 wherein the drill string component is a coupling collar.

6. The horizontal directional drilling (HDD) component of claim 5 wherein the collar utilizes a polygonal inner spline to join two drill string components together.

7. The horizontal directional drilling (HDD) component of claim 5 wherein the collar has an outer diameter between 1 and 8 inches.

8. The horizontal directional drilling (HDD) component of claim 1 wherein the drill string component is a sonar housing.

9. The horizontal directional drilling (HDD) component of claim 8 wherein the sonar housing utilizes a polygonal outer spline on the outer surface and external thread region on a boss diametrically smaller than the polygonal spline to affectively lock it to the adjacent component.

10. The horizontal directional drilling (HDD) component of claim 1 wherein the drill string component is a drill bit adapter.

11. The horizontal directional drilling (HDD) component of claim 1 wherein the drill string component is a drill bit.

12. The horizontal directional drilling (HDD) component of claim 1 wherein the drill string component is a drill pipe.

13. The horizontal directional drilling (HDD) component of claim 1 wherein the drill string component is a drill reamer.

14. The horizontal directional drilling (HDD) component of claim 1 wherein the diametrically reduced stepped geometry is a minimum of 5% and a maximum of 99% relative to the components being joined, or the component used to join them together.

15. A method of creating the horizontal directional drilling (HDD) component of claim 1 wherein the method for forming the selective hard facing comprises: melting the base material with a laser to form a melt pool; depositing a stream of particles of the clad material into the melt pool; and solidifying the melt pool to affix the particles of the hard material.

16. The horizontal directional drilling (HDD) component of claim 1 wherein the hard facing comprises a laser clad hard face coating.

17. The horizontal directional drilling (HDD) component of claim 16 wherein the hard face coating has a coating hardness greater than 50 HRC.

18. The horizontal directional drilling (HDD) component of claim 16 wherein the hard face coating comprises a matrix primarily of nickel and tungsten carbide.

19. The horizontal directional drilling (HDD) component of claim 1 wherein the hard facing comprises a Plasma Transferred Arc (PTA) hard face coating.

20. The horizontal directional drilling (HDD) component of claim 19 wherein the hard face coating has a hardness greater than 50 HRC.

21. The horizontal directional drilling (HDD) component of claim 1 wherein the hard facing comprises a mechanically bonded coating.

22. The horizontal directional drilling (HDD) component of claim 21 wherein the hard face coating has a hardness greater than 50 HRC.

23. The horizontal directional drilling (HDD) component of claim 1 wherein the hard facing is placed on a reverse thrust face of the diametrically reduced stepped geometry.

24. The horizontal directional drilling (HDD) component of claim 1 wherein the hard facing is placed on an outer diameter immediately up-string from the diametrically reduced stepped geometry.

25. The horizontal directional drilling (HDD) component of claim 1 wherein a Heat Affected Zone (HAZ) formed at the selective hard facing does not extend beyond 0.08 inch of a base material surface of the drill string component after coating.

26. A directional drilling (HDD) component assembly comprising the horizontal directional drilling (HDD) component of claim 1, and further comprising an adjacent drill string component secured to said drill string component to provide the diametrically reduced stepped geometry.

27. The horizontal directional drilling (HDD) component assembly of claim 26, wherein the adjacent drill string component includes a flange region that is sized to overlap the selective hard facing of said drill string component.

28. The horizontal directional drilling (HDD) component assembly of claim 26, wherein the adjacent drill string component includes a selective hard face including a second discrete region spaced from the first discrete region of the said drill string component and proximate the region of the diametrically reduced stepped geometry.

29. A horizontal directional drilling (HDD) component for use in a drill string comprising two or more mechanically fastened members that provide a diametrically reduced stepped geometry along a direction of drilling, the horizontal directional drilling (HDD) component comprising: a drill string component including a selective hard facing arranged to reduce accelerated wear proximate a region of the diametrically reduced stepped geometry, wherein the selective hard facing is applied along at least the smaller circumferential region for the diametrically reduced stepped geometry to a minimum axially extending length of 5% and a maximum axially extending of 50% of an outer circumference of the components being joined.

30. A horizontal directional drilling (HDD) component for use in a drill string having a plurality of assembled members that include a step in an outer profile thereof, comprising: a drill string component including a selective hard facing comprising a laser clad bead deposited upon a steel material substrate of the drill string component, wherein the drill string component is other than a drill bit and comprises: an HDD starter rod, an HDD coupling collar, an HDD sonar housing, an HDD drill bit adapter, an HDD drill pipe, or an HDD drill reamer, or any combination thereof, wherein the selective hard facing comprises a first discrete region that is arranged to be proximate the step in an outer profile of the drill string, wherein the drill string component has a predetermined recirculation zone region with the selective hard facing applied along the predetermined recirculation zone region, wherein the predetermined recirculation zone region is created at a joint location when the drill string component is arranged in overlapping relation with another of the assembled members creating the step in the outer profile, the first discrete region applied on only one drill string component allowing separability from an adjacent drill string component at the selective hard facing.

31. The horizontal directional drilling (HDD) component of claim 30, wherein a Heat Affected Zone (HAZ) formed under the laser clad bead does not extend beyond 0.08 inch of the steel material substrate after coating.

32. The horizontal directional drilling (HDD) component of claim 30, wherein the laser clad bead provides a height extending from a surface of the steel material substrate of between 0.01 and 0.25 inch.

33. A directional drilling (HDD) component assembly comprising: a first drill string component; a second adjacent drill string component secured to the first drill string component; a step defined along an outer periphery and at a joint location between the first drill string component and the second adjacent drill string component, which provides a recirculation zone region between the first drill string component and the second adjacent drill string component; and a hard facing proximate the step and along the recirculation zone region, the hard facing being: (a) applied only to the first drill string component or (b) applied only to the second adjacent drill string component or (c) applied to both of the first drill string component and the second adjacent drill string component as separate disjoined regions of the hard facing.

34. The directional drilling (HDD) component assembly of claim 33, wherein the hard facing is applied within 0 to 30 centimeters of the step.

35. The directional drilling (HDD) component assembly of claim 34, wherein the step is formed by a radially extending surface extending radially outward away from a first annular surface of the first drill string component toward a second annular surface of the second adjacent drill string component, wherein the hard facing is applied along at least a portion of: the radially extending surface, the first annular surface or the second annular surface, or any combination thereof.

36. The directional drilling (HDD) component assembly of claim 35 wherein the hard facing is applied along at least portions of at least two of the radially extending surfaces, the first annular surface and the second annular surface.

37. The directional drilling (HDD) component assembly of claim 35 wherein the hard facing is applied along at least portions of all three of the radially extending surfaces, the first annular surface and the second annular surface.

38. The directional drilling (HDD) component assembly of claim 33, wherein the hard facing is applied to less than 50% of an exposed external surface area of the first drill string component and the second adjacent drill string component.

39. The horizontal directional drilling (HDD) component of claim 33, wherein the first drill string component and the second adjacent drill string component comprise a base material comprising an iron or steel material, wherein the hard facing comprises a laser clad bead applied to the iron or steel material, and wherein the laser clad bead provides a height extending from a surface of the steel material substrate of between 0.01 and 0.25 inch.

40. The horizontal directional drilling (HDD) component of claim 33, wherein the second adjacent drill string component comprises a collar slidable over the first drill string component, the hard facing being applied to a reverse thrust face of the collar and an outer circumference of the collar, and applied along the first drill string component adjacent the reverse thrust face.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

(2) FIG. 1 is an exploded schematic side view of the cutting end of the drill string. This figure shows the separate components to the drill string starting from left to right, including but not limited to the starter rod, coupling collar, sonar housing, bit adapter, and boring bit.

(3) FIG. 2 is an assembled schematic side view of the cutting end of the drill string. This figure shows how the components fit together and the resulting geometry of the final drill string members.

(4) FIGS. 3A-3D are assembly schematic side views showing the required steps in sequence A-D for coupling HDD drill string components together. The primary components in this example include the starter rod, coupling collar, and sonar housing.

(5) FIG. 4 is a partly schematic side view of the coupling joint provided by the collar and between the starter rod and the sonar housing described in FIGS. 1, 2 and 3, and better showing the stepped geometry created by the coupling collar over the starter rod.

(6) FIG. 5 is a schematic illustration of a flow contour solved over a simulated geometry representative of FIG. 4, with velocity contours of the flow showing the large recirculation zone present directly behind the collar.

(7) FIG. 6 is an exaggerated schematic cross section through a central axis of the starter rod showing the location of the recirculation and potential cavitation zone.

(8) FIG. 7 is an exaggerated schematic cross section through a central axis similar to FIG. 6, but additionally and in accordance with an embodiment of the present invention depicting a single layer cladded surface of the starter rod and coupling collar. Also, of functional advantage, the hard face layer on the starter rod may not exceed the inner diameter of the coupling collar.

(9) FIG. 8 is an exaggerated schematic cross section axially through a single layer of cladded surface of the starter rod and coupling collar that was shown in FIG. 7 during assembly with the collar installed over the cladding on cladded surface of the starter rod, such that it can be seen that the hard face coating on the starter rod does not exceed the inner diameter of the coupling collar.

(10) FIG. 9 is an exaggerated cross section schematic of the starter rod shown in FIGS. 7 and 8, but additionally schematically showing the minimal heat affected zone (HAZ). The HAZ is shown below the hard face coating for scale.

(11) FIG. 10 is a side schematic of the starter rod and coupling collar of that shown in FIGS. 7-9 (but not a cross-section) and additionally with sonar housing complete with hard face coating (e.g. laser clad beads) applied in the appropriate region of stepped geometry.

(12) FIG. 11 is a generic drawing of another stepped geometry of one or more drill string components to which this inventive method may be applied with the hard facing such as laser clad beads being applied proximate the stepped surfaces.

(13) FIG. 12 is a general diagram showing a typical HDD unit and drill string. Of note are the directions of “Up string” and “Down string” used in the description herein.

(14) While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

(15) The present application relates to improving the wear characteristics of any HDD drill string component or joint that experiences rapid wear.

(16) In particular, in an embodiment, any of the HDD drill string components illustrated or described above may be subjected to the hard face coating wear improvement.

(17) In greater detail and turning to the Figures, an embodiment of the present invention in FIGS. 1-10 is illustrated as a drill string assembly 10 (aka “drill string”). In FIGS. 1 and 2, and 4-6, the drill string assembly components are illustrated without the hard facing applied (e.g. prior to hard facing application), whereas in FIGS. 3, 7-10, one or more hard facing regions 12, 14 are applied.

(18) For example, the hard face regions 12, 14 can be applied to create selective hard facing that is arranged to reduce accelerated wear proximate a region of the diametrically reduced stepped geometry provided by a step region 16.

(19) In the illustrated embodiment, the drill string assembly comprises: a starter rod 18, a starter rod collar 20, a sonar housing 22, optionally a housing or bit adapter 24, and removable boring bit 26. Each of these components may be referred to individually as a horizontal directional drilling (HDD) component” and/or a “drill string component, or similar. However, other assemblies with more or less components are intended to be covered, and in some embodiments a single horizontal directional drilling (HDD) component may be covered.

(20) As apparent from the figures, each horizontal directional drilling (HDD) component is for use in a drill string comprising two or more mechanically fastened members that can provide a diametrically reduced stepped geometry along a direction of drilling such as provided by the step 16, which in this case is between the collar 20 and the starter rod 18.

(21) Fastening may be accomplished between adjacent horizontal directional drilling (HDD) components as illustrated via steps schematically shown in FIGS. 3A-3D, such as using threaded attachment, spline attachments, pins, and/or other such couplers. For example, the sonar housing 22 can be equipped to receive the boring bit 26 such as via an optional sub adapter 24 on one end via spline and/or threads. The sonar housing 22 can be coupled to the starter rod 18 on the other via the locking collar 20. The collar 20 can have a splined region may have any geometry on the inner surface 28, that matches that of the outer surface 30 of the starter rod 18 and the outer surface 32 of the sonar housing 22. For example, a polygonal spline for the spined surfaces 28, 20, 32 is the most common geometry used in either a hex or octagon form.

(22) To couple the two members together in the present embodiment, the collar 20 is slid onto the starter rod 18, which may be attached to the main drill string prior to attaching the sonar housing 22 and the drill bit 26 (See FIG. 3a). With the collar 20 on the starter rod 18, the sonar housing 22 is threaded onto the starter rod 18 (FIG. 3b-3c), via interlocking rod thread 34 and housing thread 36, in which one may be a threaded receptacle and the other a threaded boss, respectively or vice versa. When the sonar housing 22 is screwed on completely, the unit is rotated counter clockwise until the starter rod outer coupling geometry (e.g. outer surface 30) meets up with the sonar housing coupling geometry (e.g. outer surface 32), as shown in FIG. 3c. When the two components are lined up the collar 20 is slid over the starter rod 18 and across the joint between the sonar housing 22 and the starter rod 18. A pin 38 or bolt can then tightly fit into the collar 20 through the sonar housing 22 thus locking the three pieces together.

(23) As apparent, the starter rod 18 can utilize a polygonal spline on the outer surface and internal threads on the inner diameter to affectively lock it to the adjacent component.

(24) Similarly, the collar 20 can utilize a polygonal inner spline to join two drill string components together.

(25) Also similarly, the sonar housing 22 can utilize a polygonal outer spline on the outer surface and external threads on a boss diametrically smaller than the polygonal spline to affectively lock it to the adjacent component.

(26) While the location at step 16 is illustrated to be hard-faced, other locations along the drill string may be hard faced in addition or in the alternative to regions 12, 14, especially but not limited to stepped regions.

(27) For example, in different embodiments, the hard faced horizontal directional drilling (HDD) component may be one or more of the following: the HDD coupling collar 20, the HDD sonar housing 22, the HDD drill bit adapter 24, the HDD drill bit (i.e. boring bit 26), an HDD drill pipe, an HDD drill reamer.

(28) The selective hard facing provided by one or more of the hard face regions 12, 14 can be arranged to reduce accelerated wear proximate a region of the diametrically reduced stepped geometry. As shown in FIG. 7 (with additional reference to FIGS. 4 and 5 showing the recirculation zone created from the stepped outer surface profile), the diametrically reduced stepped geometry is provided at the step 16 which is created at a joint location when one drill string component (in this case starter rod 18) is arranged in overlapping relation with another one of the mechanically fastened members (in this case collar 20). In this manner due to the step, the drill string component has a predetermined recirculation zone region (see FIG. 5) for which the selective hard facing 12, 14 (e.g. laser clad beads 46) are applied along the predetermined recirculation zone region.

(29) For example, the hard face coating can be placed on the reverse thrust face 40 of the stepped geometry.

(30) As another example, the selective hard facing can placed on the outer diameter 42 immediately up-string from the stepped geometry, such as on the forward surface region of the starter rod 18.

(31) Yet as another example, the selective hard facing can be placed at the outer circumferential surface 44 of such a step, such as at the up-string corner 45 of the sonar housing 22 (that is therefore down-string from the step).

(32) Accordingly, in one or more and preferably all of these regions of the step, selective hard facing can counteract the increased wear that can be realized in a stepped assembly as indicated by FIG. 5.

(33) Preferably, selective hard facing as provided by the hard face regions 12, 14 can be created by laser cladding with one or more laser clad beads 46. For example, 6 different rings of laser clad beads 46 may be used as illustrated in the figures, although fewer or more beads may be laid upon the steel material substrate.

(34) Preferably, the laser clad beads 46 are relatively thin depositions to minimize impact to part diameters and reduce impact relative to flow or frictional engagements. For example, the laser clad bead can provide a height extending from a surface of the steel material substrate of between 0.01 and 0.25 inch.

(35) An advantage of using a laser clad bead 46 is that the Heat Affected Zone (HAZ) 48 (shown schematically in FIG. 9) may be limited, such as not extending beyond 0.08 inch of the base material surface after coating. This advantageously can prevent soft zones that may create erosion zones in the base material. Laser cladding may also heat treat the underlying base material.

(36) The present disclosure also contemplates that other drill string components may be subject to laser cladding other than the drill bit, for example, such HDD component may be at least one of an HDD starter rod, an HDD coupling collar, an HDD sonar housing, an HDD drill bit adapter, an HDD drill pipe, and an HDD drill reamer.

(37) As shown in FIG. 12, the drill string assembly 10 can be used for use in cutting and boring applications, such as for horizontal directional drilling applications. This may be used for placement or cables, wires, conduits or other situations where a directed bore and/or drill hole is desired. The sonar housing 22 will typically house a sonar transponder or other sonar emitter that can indicate location of the drill string assembly 10, to facilitate guidance of the drilling by an operator.

(38) From the foregoing description and for other embodiments a few additional observations and/or potential useful features in various embodiments are detailed below.

(39) The features may be particularly beneficial in a directional drilling (HDD) component assembly such as provided by drill string assembly 10. This may include at least a first drill string component and a second adjacent drill string component secured to the first drill string component, which are selected from at least two of the following: the starter rod 18, the starter rod collar 20, the sonar housing 22, optionally the housing or bit adapter 24, and the removable boring bit 26. A step provided by step region 16 is defined between the first drill string component and the second adjacent drill string component. For example as shown in the Figures a step is provided by step region formed by the collar 20 and the starter rod 18, but it may be at other step regions similarly. As discussed above hard facing applied to a region of at least one of the first drill string components and the second adjacent drill string component, the region being proximate the step.

(40) Preferably, the hard facing (e.g. hard facing regions 12, 14) is applied within 0 to 30 centimeters of the step and more preferably within 0 to 15 centimeters of the step.

(41) As shown in the figures, the step may be formed by a radially extending surface (for example, the reverse thrust face 40).

(42) Further, this radially extending surface may extend radially outward away from a first annular surface (for example, the outer diameter 42) of the first drill string component toward a second annular surface (for example, the outer circumferential surface 44) of the second adjacent drill string component.

(43) The hard facing may be applied along at least a portion of at least one, more preferably two and most preferably all three of the radially extending surfaces, the first annular surface and the second annular surface as show.

(44) Further, it is advantageous if the hard facing is selective as shown. In particular, substantial benefit is obtained by very limited application to the exposed external surface as shown in the drawings. For example, the hard facing may be applied to less than 50% of an exposed external surface area of the first drill string component and the second adjacent drill string component, and even more preferably less than 20% of the exposed external surface area of the assembly (as shown in the drawings, it may even be less than 10% of the surface area).

(45) Typically, the first drill string component and the second adjacent drill string component comprise a base material comprising an iron or steel material. Further, the hard facing (hard facing regions 12, 14) may comprise a laser clad bead (e.g. one or more applied beads) applied to the iron or steel material, and preferably the laser clad bead provides a height extending from a surface of the steel material substrate of between 0.01 and 0.25 inch.

(46) As shown, the second adjacent drill string component comprises a collar slidable over the first drill string component, with the hard facing being applied to a reverse thrust face of the collar and an outer circumference of the collar, and applied along the first drill string component adjacent the reverse thrust face. However, this is equally applicable to steps between other drill string components.

(47) The component(s) being hard faced may reside in a location of radially stepped geometry created by the coupling members, or by one individual member either through additive or subtractive manufacturing.

(48) The component(s) can be used in conjunction with a drilling fluid, primarily water mixed with bentonite, whose intended purpose is, but not limited to, aid in the evacuation of the drill cuttings.

(49) Hard facing preferably via laser deposition may be placed cylindrically on the shaft of the component proximally up string of the stepped geometry.

(50) Hard facing via laser deposition may be placed on the reverse thrust face of the stepped geometry.

(51) The hard facing may be comprised of an amorphous alloy, which upon solidification creates boron carbides. This method of hard facing yields a very evenly distributed deposition that possesses hardness in excess of 50 HRC.

(52) The base material for any and/or all of the drill string components may comprise a softer material than the hard facing, most typically steel material.

(53) The hard face coating may be integrally bonded to the boring component body over the steel base material thereof.

(54) As schematically indicated in FIGS. 7 & 9, the hard faced layer is preferably applied to both the radial shaft area directly up string of the stepped geometry as well as the reverse thrust face of the stepped geometry. Both regions may have the same average coating thickness.

(55) The hard face coating may be thin enough to allow any mechanical members to continue operating as original intent. Where this is most desirable is in areas of overlap, and in particular for example where the collar has an annular flange region 50 that overlaps cladding upon the starter rod during the assembly process as shown in FIG. 8.

(56) The hard face coating may be deposited in such a way to create veins or channels to aid in the fluid evacuation, and may be spirally (e.g. helically) wound about a surface, but in other embodiments, annularly, being one or more annular rings of cladding (e.g. the Figures show 3 rings of cladding for each hard face coating although fewer or more rings and/or side-by-side depositions may be applied).

(57) To provide additional reference, a typical boring bit geometry was demonstrated in the Figures by the drill string assembly 10 (with hard facing at a joint between sonar and starter rod). However, other assemblies with more or less components are intended to be covered and other locations along the drill string may be hard faced. The drill string may comprise the sonar housing, starter rod collar, and starter rod, as well as a removable boring bit. The collar embodies a reverse thrust face geometry that may be hard faced, while the starter rod contains the cylindrical shaft geometry that may be hard faced. This is just one portion of the drill string that can encounter recirculation zones and cavitation, and other regions may also be hard faced.

(58) Preferably, the hard face coating extends the entire length of the re-circulation zone, and completely around the perimeter of the component such as shown in the embodiments of FIGS. 7-10. Coating coverage can be reduced both axially in length, and rotationally around the component, but the most effective coating will be the preferred method.

(59) However, in some embodiments, selective application that does not extend completely around the perimeter may be applied. For example, some benefit is realized even in less than complete perimeters, as in the embodiment of FIGS. 7-10; but may also be advantageous in other configurations with irregular steps such as in FIG. 11 that also provide a diametrically reduced stepped geometry.

(60) Also, the hard face coating preferably covers the entire reverse thrust face of stepped geometry. This surface also sees re-circulation wear attributes.

(61) Preferably the hard face coating is applied proximate the region of the diametrically reduced stepped geometry, and that may be within 10 times a radial thickness of the step, and more preferably closer within 5 times radial thickness of the step. Such hard facing may be within 0 to 6 inches, more preferably within 0 to 3 inches of the step.

(62) However, hard facing alternatively or additionally may be applied to other regions on the drill string components, preferably with laser cladding.

(63) Laser cladding beads may be generated thinner and/or with not the same heat affected zone (HAZ) as per weld face hard facing. As a result, a significant advantage can be achieved with laser cladding on drill string components that have thickness considerations relative to HAZ and/or hard facing thicknesses.

(64) For example, as shown in FIG. 7, the laser clad bead provides a height (either axial or radial depending upon applied bead) extending from a surface of the steel material substrate of between 0.01 and 0.5 inch, more preferably between 0.01 and 0.25 inch.

(65) Also, a Heat Affected Zone (HAZ) formed under the laser clad bead does not extend beyond 0.125 inch of the steel material substrate after coating, more preferably less than 0.08 inch.

(66) Generally, while the description above is an effective and efficient embodiment of the invention, it should be understood that the invention is not limited to just the above configuration.

(67) In a Horizontal Directional Drilling (HDD) operation utilizing a liquid slurry the drill string components may be selectively hardened to extend life and control wear characteristics. A drill string may be composed of a bit, sonar housing, and starter rod where said components are attached together via locking collars, threads and splines used in conjunction with a liquid slurry wherein the slurry is directed along the drill string.

(68) All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

(69) The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention

(70) Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

(71) All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.