Nickel-based wear / corrosion-resistant shank adapter

Abstract

A shank adapter for forming part of a hole boring assembly, comprising a longitudinal axis, an outer surface, an inner surface, a threaded portion provided at a front end portion and a plurality of splines provided at a rear end portion, and a machine portion extending axially between the threaded portion and the splines, wherein at least a portion of the outer surface is coated with a first corrosion-resistant layer containing nickel. In the shank adapter, at least a portion of the first corrosion-resistant layer is coated with a polymer-based sealant top layer.

Description

Technical Field

[0001] The present invention relates to a shank adapter for top hammer rock drilling having a corrosion resistant and / or wear resistant layer.

Background Art

[0002] A shank adapter is used in a rock drill as a main component that transmits impact energy from a piston to a drill string while rotating. Further, the shank adapter is used to flow a flushing medium from the rock drill into the drill string. Since the shank adapter needs to have high impact resistance, it is usually made of high-strength carburized steel. However, a drawback of this material is that it is corroded by a flushing medium that may contain, for example, chlorides, sulfides, or other ions that accelerate corrosion. When the shank adapter is corroded, its functionality deteriorates. The steel material can cause problems due to stress corrosion cracking, for example, because the mechanical strength of the material decreases.

[0003] Furthermore, in order to prevent leakage of the flushing water and maintain a good flushing pressure, it is important to maintain the integrity of the sealing portion inside the flushing housing. In order not to prematurely wear the sealing portion, it is important that the surface of the shank adapter in contact with the sealing portion remains in a good non-corroded state. The corroded surface is extremely rough and leads to premature damage of the sealing portion in the flushing housing of the rock drill.

[0004] Therefore, it is advantageous to apply a corrosion resistant coating to the surface of the shank adapter.

[0005] A known corrosion-resistant method for a shank adapter is to provide a layer of hard chromium plating on the surface. However, the hard chromium layer has pores and microcracks, and these pores and microcracks serve as paths for water to penetrate and reach the surface of the shank adapter, and as a result, the corrosion resistance may be removed. Therefore, the problem to be solved is how to realize a method for improving the corrosion resistance and / or wear resistance of the surface of the shank adapter.

Summary of the Invention

[0006] An object of the present invention is to provide means for enhancing the corrosion resistance and / or wear resistance of a shank adapter. This object is achieved by providing a shank adapter for forming part of a drilling assembly, comprising a longitudinal axis, an outer surface, an inner surface, a threaded portion provided at the front end portion and a plurality of splines provided at the rear end portion, and a mechanical portion extending axially between the threaded portion and the splines, wherein at least a part of the outer surface is coated with a first corrosion-resistant layer containing nickel, and in the shank adapter, at least a part of the first corrosion-resistant layer is coated with a polymer-based sealing material top layer.

[0007] Advantageously, by combining a nickel-based corrosion-resistant layer with a polymer-based sealing material surface sealant, the opening cracks and defects between the outside air and the steel base material are reduced, and as a result, an improvement in corrosion resistance is achieved. This combination of coatings forms a corrosion-resistant layer on the shank adapter and around the flushing slots, thereby delaying the propagation of radial cracks at the shank diameter, and thus delaying the transverse breakage of the screw or mechanical portion. Furthermore, this combination of coatings forms a low-friction surface. The low-friction coating is advantageous for reducing the wear of the flushing seal and other rock drilling components, thereby further extending the service life of the seal. Furthermore, this solution achieves high wear resistance and a reduction in galling.

[0008] In one embodiment, at least a portion of the inner surface is coated by the first corrosion-resistant layer and / or the top layer of the polymeric sealant. Advantageously, this provides protection against cavitation inside the shank adapter, as well as corrosion resistance, similar to the outside, thus extending the life of the shank adapter.

[0009] In one embodiment, the thickness of the first corrosion-resistant layer is 5 - 200 μm. Advantageously, this thickness provides an optimal balance between achieving sufficient corrosion and wear resistance and not incurring excessive costs.

[0010] In one embodiment, the thickness of the top layer of the polymeric sealant is 0.5 - 10 μm. Advantageously, this provides an optimal balance between having a sufficiently effective thickness, not incurring unnecessary costs, and not increasing the risk of wire scratches as the coating dries. The polymeric flashing surface layer can also penetrate into cracks, thereby further increasing adhesion and corrosion resistance.

[0011] In one embodiment, the first corrosion-resistant layer is a nickel-phosphorus alloy. Advantageously, nickel-phosphorus forms a hard coating, thereby increasing wear resistance.

[0012] In one embodiment, the phosphorus content of the nickel-phosphorus alloy is 6 - 9 weight percent (wt%). Advantageously, this phosphorus content increases wear without undesirable brittleness.

[0013] In one embodiment, the top layer of the polymeric sealant comprises a polymer having a coefficient of friction of 0.05 - 0.15. Advantageously, the low-friction coating is beneficial for reducing wear of the flashing seal and other rock drilling components, thereby further extending the service life of the seal.

[0014] In one embodiment, the first corrosion-resistant layer and the outermost polymer-based sealing material layer are disposed on the mechanical part. Advantageously, this provides corrosion resistance to the region of the shank adapter that is most exposed to corrosion and where protection from corrosion is most important.

[0015] In one embodiment, the first corrosion-resistant layer and the outermost polymer-based sealing material layer are disposed on all parts of the shank adapter. Advantageously, this provides a highly comprehensive corrosion resistance.

[0016] In one embodiment, the rear end portion of the shank adapter, known as the striking surface, is not coated separately. Advantageously, this avoids unwanted peeling in this region that could clog the circulation system and cause damage.

[0017] Another aspect of the present invention is a method for applying a corrosion-resistant treatment to the above or below-described shank adapter, comprising: - Depositing a first corrosion-resistant layer containing nickel on at least a portion of the outer surface of the shank adapter; - Depositing an outermost polymer-based sealing material layer on top of the first corrosion-resistant layer; - Heat-treating the coated shank adapter and including, a method.

[0018] Advantageously, this method provides a highly effective corrosion protection for the shank adapter and a means for applying a low-friction and high-wear-resistant coating.

[0019] In one embodiment, the first corrosion-resistant layer is deposited using an electroless nickel bath. Advantageously, this method is fast and less harmful to the environment compared to chromium plating. Another advantage of this method is that it is possible to apply a more uniform coating with a thickness due to high reproducibility.

[0020] In one embodiment, the outermost polymer-based sealing material layer is sprayed. Advantageously, this method provides a coating with a uniform thickness.

[0021] In one embodiment, the heat treatment is carried out at a temperature of 150 to 300 °C for 30 to 120 minutes. Advantageously, this temperature range provides a balance between having a high enough temperature and heating time to form a hard and wear-resistant surface and not having an excessive temperature and time that would adversely affect the hardening characteristics of the steel substrate.

[0022] In one embodiment, before the nickel-based corrosion-resistant layer is deposited, the surface of the shank adapter is shot-peened or blasted. Advantageously, this step enhances the adhesion of the corrosion-resistant layer to the surface of the shank adapter.

[0023] Next, specific implementations of the present invention will be described by way of example with reference to the accompanying drawings.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0025] Figure 1 shows a shank adapter 2 for forming part of a trepanning assembly. The shank adapter 2 includes a longitudinal axis 4, an outer surface 6, an inner surface 8, a threaded portion 10 provided at a front end portion 12, a plurality of splines 32 protruding radially outwardly provided at a rear end portion 14, and a machine portion 16 (otherwise known as a body) extending axially between the threaded portion 10 and the splines 32. The splines 32 are engaged by corresponding splines of a drive bushing of a rotary motor (not shown), thereby being configured to rotate the shank adapter 2 about the axis 4 during the trepanning operation. The threaded portion 10 may be either a male thread or a female thread. The shank adapter further includes a flushing slot 26 that provides an entrance to a flushing hole or lumen (not shown) that extends radially through the machine portion 16 in the form of an internal cavity. The shank adapter 2 is configured to couple to an elongate drill string and transmit a stress wave to a drill bit (not shown) located at the deepest part of the drill hole, thereby transmitting an impact trepanning action. Specifically, the front end portion 12 can be coupled to the rear end portion or a coupling (not shown) of the rearmost elongate drill rod that forms part of the drill string. The rear end portion 14 is otherwise known as a striking surface and is configured to contact a hydraulically driven piston (not shown) that generates a stress wave within the shank adapter 2 and the drill string. Optionally, the front end portion 12 further includes an annular shoulder 28 from which the threaded portion 10 projects axially. Optionally, a reduced diameter portion 30 is disposed axially between the machine portion 16 and the threaded portion 10.

[0026] Figure 2 shows that at least a portion of the outer surface 6 of the shank adapter 2 is coated by a first corrosion-resistant layer 18 containing nickel. At least a portion of the first corrosion-resistant layer 18 is coated by a polymeric sealant top layer 20. Regions of the outer surface 6 of the shank adapter 2 that are not coated by the first corrosion-resistant layer 18 can also be coated by the polymeric sealant top layer 20. A portion or all of the first corrosion-resistant layer 18 can be coated by the polymeric sealant top layer 20.

[0027] At least a portion of the inner surface 8 of the shank adapter 2 can also be coated by a first corrosion-resistant layer 18 and / or a polymer-based sealant top layer 20. The inner surface 8 of the shank adapter 2 includes a flushing slot 26 and a flushing hole / lumen that extends radially through the machine part to a threaded opening. At least a portion or all of the inner surface 8 can be coated only with the first corrosion-resistant layer 18. At least a portion or all of the inner surface 8 can be coated only with the polymer-based sealant top layer 20. At least a portion or all of the inner surface can be coated with both the first corrosion-resistant layer 18 and the polymer-based sealant top layer 20. Any combination of these options is possible.

[0028] In one embodiment, the thickness of the first corrosion-resistant layer 18 is 5 to 200 μm, more preferably 7 to 100 μm, and even more preferably 10 to 50 μm.

[0029] In one embodiment, the thickness of the polymer-based sealant top layer 20 is 0.5 to 10 μm, preferably 0.5 to 5 μm.

[0030] The first corrosion-resistant layer 18 can be nickel alloyed with sulfur, phosphorus, boron, or any other suitable element. Preferably, the first corrosion-resistant layer 18 is a nickel-phosphorus alloy. Preferably, the phosphorus content of the nickel-phosphorus alloy is 6 to 9 wt%.

[0031] In one embodiment, the polymer-based sealant top layer 20 includes a polymer having a coefficient of friction of less than 0.05 to 0.15, preferably less than 0.1 to 0.13. For example, the polymer can be Teflon, a fluorinated polymer (such as polytetrafluoroethylene (PTFE)), a non-fluorinated crystalline polymer (such as polyetheretherketone (PEEK)), or a high-density polymer (such as ultra-high molecular weight polyethylene (UHMWPE)).

[0032] In one embodiment, the first corrosion-resistant layer 18 and the polymer-based encapsulant top layer 20 are disposed on the mechanical portion 16. In one embodiment, the first corrosion-resistant layer 18 and the polymer-based encapsulant top layer 20 are disposed only on the mechanical portion 16. In other words, the first corrosion-resistant layer 18 is not disposed on the spline 32 or the threaded portion 10. Alternatively, the entire outer surface 6 of the shank adapter 2 is coated with the first corrosion-resistant layer 18 and the polymer-based encapsulant top layer 20.

[0033] In one embodiment, the first corrosion-resistant layer 18 and the polymer-based encapsulant top layer 20 are disposed inside the flushing slot 26, as a result of which damage to the mechanical portion is reduced.

[0034] In one embodiment, the first corrosion-resistant layer 18 and the polymer-based encapsulant top layer 20 are disposed on the threaded portion 10.

[0035] In one embodiment, the rear end portion / striking portion 14 of the shank adapter 2 remains uncoated. In other words, the first corrosion-resistant layer 18 and the polymer-based encapsulant top layer 20 are not provided on the rear end portion / striking portion 14 of the shank adapter. In one embodiment, all portions of the shank adapter 2 except the rear end portion / striking surface 14 are coated with the first corrosion-resistant layer 18 and the polymer-based encapsulant top layer 20.

[0036] The present application further relates to a method for subjecting the shank adapter 2 to a corrosion-resistant treatment, the method comprising a) depositing a first corrosion-resistant layer 18 containing nickel on at least a portion of the outer surface 6 of the shank adapter 2; b) depositing a polymer-based encapsulant top layer 20 on top of the first corrosion-resistant layer 18; c) heat-treating the coated shank adapter 20 and including.

[0037] In one embodiment, the first corrosion-resistant layer 18 is deposited using an electroless nickel bath. Nickel or a nickel-based alloy adheres to the substrate, which is the metal of the shank adapter. In electroless nickel plating, the object reacts with the chemicals in the plating bath to produce a uniform and smooth layer with very slight surface porosity. Since the deposition is uniform, nickel plating is an ideal choice for complex, hidden geometries and often eliminates the need for post-plating polishing. Alternatively, the first corrosion-resistant layer may be deposited by electroplating or any other suitable method.

[0038] In one embodiment, the polymeric sealant top layer 20 is sprayed. Alternatively, the polymeric sealant top layer 20 can be deposited by dipping or any other suitable method.

[0039] The purpose of the heating step is to enable the formation of the Ni-P intermetallic phase, improve adhesion to the substrate, and cure the polymeric sealant top layer. Typically, the heat treatment is carried out in a furnace.

[0040] In one embodiment, the heat treatment is carried out at a temperature of 150 - 300 °C, preferably 225 - 260 °C. In one embodiment, the heat treatment is carried out for 30 - 120 minutes, preferably 45 - 75 minutes.

[0041] The same method can be used to deposit the first corrosion-resistant layer 18 and / or the polymeric sealant top layer 20 on the inner surface 8 of the shank adapter 2.

[0042] In one embodiment, the surface of the shank adapter (2) is shot-peened or blasted before depositing the nickel-based corrosion-resistant layer (18).

[0043] The above or below shank adapter can be part of a drill string and / or a drill rig device.

Examples

[0044] Summary of the shank adapters tested Table 1 shows the corrosion resistance treatment applied to the shank adapter used in the field test. TIFF2025521107000002.tif50170

[0045] Field Test 1 The field test was conducted in a mine in Sweden. The drilling meters and drilling duration were recorded for each of the test shank adapters. In this test, both shank adapters were damaged after a similar number of drilling meters, but the causes of the damage were different. For the chromium-type comparative shank adapter B, exfoliation wear corrosion sites were observed, indicating that corrosion was the main reason for the damage. The shank adapter A of the present invention showed no exfoliation wear corrosion sites and significantly less normal corrosion compared to shank adapter B. Instead, the shank adapter A of the present invention was damaged by screw wear. Therefore, for the comparative shank adapter B, corrosion became a limiting factor for the life of the shank adapter, but for the shank adapter A of the present invention, this was not the case after approximately the same number of drilling hours.

[0046] Field Test 2 Another field test was conducted in a mine in Australia. Table 2 shows the number of drilling hours before the shank adapter was damaged. TIFF2025521107000003.tif34170

[0047] The shank adapter A of the present invention significantly outperformed the comparative shank adapter B in terms of the number of drilling meters before damage, indicating that the life of the shank adapter with corrosion resistance according to the present invention has been significantly increased.

[0048] Field Test 3 Yet another field test was conducted at a mine in India where significant problems due to corrosion do not usually occur. Compared with the comparative shank adapter C, it was found that the life of the shank adapter A of the present invention was improved by 27%. It was confirmed that the shank adapter A of the present invention did not break inside the rock drill and the service life of the sealing part inside the rock drill was improved.

Claims

1. A shank adapter (2) for forming part of a drilling assembly, comprising: a longitudinal axis (4); an outer surface (6); The inner surface (8) a threaded portion (10) at the front end (12) and a plurality of splines (32) at the rear end (14); a mechanical portion (16) extending axially between the threaded portion (10) and the spline (32); Equipped with A shank adapter (2) in which at least a portion of the outer surface (6) is coated with a first corrosion-resistant layer (18) comprising nickel, At least a portion of the first corrosion-resistant layer (18) is coated with a polymeric encapsulant top layer (20). A shank adapter (2).

2. The shank adapter (2) of claim 1, further comprising at least a portion of the inner surface (8) coated with the first corrosion-resistant layer (18) and / or the polymeric sealant top layer (20).

3. The shank adapter (2) according to claim 1 or 2, wherein the thickness of the first corrosion-resistant layer (18) is 5 to 200 μm.

4. The shank adapter (2) according to claim 1, wherein the thickness of the polymer-based sealant top layer (20) is 0.5 to 10 μm.

5. The shank adapter (2) of claim 1, wherein the first corrosion-resistant layer (18) is a nickel-phosphorous alloy.

6. The shank adapter (2) according to claim 5, wherein the nickel phosphorus alloy has a phosphorus content of 6 to 9 wt%.

7. The shank adapter (2) of claim 1, wherein the polymer-based sealant top layer (20) comprises a polymer having a coefficient of friction of 0.05 to 0.

15.

8. The shank adapter (2) of claim 1, wherein the first corrosion-resistant layer (18) and the polymeric sealant top layer (20) are disposed on the mechanical portion (16).

9. The shank adapter (2) of claim 1, wherein the first corrosion-resistant layer (18) and the polymeric sealant top layer (20) are disposed on all portions of the shank adapter (2).

10. The shank adapter (2) of claim 1, wherein the rear end (14) of the shank adapter (2) is uncoated.

11. 2. A method for providing corrosion resistance to a shank adapter (2) according to claim 1, comprising: depositing a first corrosion resistant layer (18) comprising nickel on at least a portion of said outer surface (6) of said shank adapter (2); - depositing a polymeric encapsulant top layer (20) on said first corrosion resistant layer (18); - heat treating the coated shank adapter (2); A method comprising:

12. The method of claim 11, wherein the first corrosion resistant layer (18) is applied using an electroless nickel bath.

13. 13. The method according to claim 11 or 12, wherein the polymeric sealant top layer (20) is sprayed on.

14. 13. The method according to claim 11 or 12, wherein the heat treatment is carried out at a temperature of 150 to 300° C. for 30 to 120 minutes.

15. A method as described in claim 11 or 12, wherein the surface of the shank adapter (2) is shot peened or blasted before the first corrosion-resistant layer (18) is applied.

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