COMPOSITE MATERIAL WITH COATED DIFFUSED LAYER

Abstract

A composite material includes a substrate that is thermochemically treated in order to harden the surface thereof and that is, therefore, not subject to deformations as a result of high stresses sustained by the outer layer. The composite material also includes an adhesion layer overlying the treated layer. Subsequently, an intermediate layer and a DLC (Diamond Like Carbon) layer are added, wherein the DLC layer has a structure based on an amorphous carbon film. The composite material may be used in valves built into submarine equipment. The composite material is thermochemically treated and comprises a treated substrate and an adhesion layer onto which is disposed an intermediate layer that receives a final DLC layer. All of these layers are disposed on the surface of a substrate of a gate valve.

Claims

1. A composite material with a coated diffused layer for low-friction coating on valve seats and gates, comprising, in successive layers, a treated substrate onto which an adhesion layer is disposed and onto which an intermediate layer supporting a final diamond like carbon (DLC) layer is disposed, wherein said treated substrate is treated by a thermochemical diffusion process before receiving said adhesion layer.

2. The composite material with the coated diffused layer according to claim 1, wherein the treated substrate is a layer external to a substrate, wherein said substrate is an austenitic alloy.

3. The composite material with the coated diffused layer according to claim 2, wherein the austenitic alloy is a nickel alloy.

4. The composite material with the coated diffused layer according to claim 1, wherein the treated substrate is lapped after the thermochemical diffusion process and before the adhesion layer is applied onto.

5. The composite material with the coated diffused layer according to claim 1, wherein the treated substrate is formed by treating the substrate with one of Kolsterising process, Balitherm process or mixing and friction thermomechanical process.

6. The composite material with the coated diffused layer according to claim 5, wherein the thermochemical treatment is Kolsterising.

7. The composite material with the coated diffused layer according to claim 1, wherein the adhesion layer is chromium or silicon.

8. The composite material with the coated diffused layer according to claim 7, wherein the adhesion layer is chromium.

9. The composite material with the coated diffused layer according to claim 1, wherein the intermediate layer is tungsten carbide (WC).

10. The composite material with the coated diffused layer according to claim 1, wherein the intermediate layer comprises a hardness in a range of 22 to 25 Gpa.

11. The composite material with the coated diffused layer according to claim 1, wherein the intermediate layer is deposited by a physical vapor deposition (PVD) process.

12. The composite material with the coated diffused layer according to claim 11, wherein the physical vapor deposition (PVD) process is a magnetron sputtering process.

13. The composite material with the coated diffused layer according to claim 1, wherein the DLC layer is a hydrogenated amorphous type and has a hydrogen content of approximately 27%.

14. The composite material with the coated diffused layer according to claim 1, wherein the DLC is deposited by chemical vapor deposition (CVD) or plasma-enhanced chemical vapor deposition (PECVD).

15. The composite material with the coated diffused layer according to claim 1, wherein the DLC layer comprises a hardness in a range of 22 to 25 Gpa.

16. The composite material with the coated diffused layer according to claim 1, wherein the DLC layer comprises a coefficient of friction between 0.05 and 0.2.

17. The composite material with the coated diffused layer according to claim 16, wherein the DLC layer comprises a coefficient of friction between 0.05 and 0.1.

18. The composite material with the coated diffused layer according to claim 1, wherein a thickness of the treated substrate ranges from 10 to 30 micrometers, a thickness of the adhesion layer is about 0.5 micrometer, a thickness of the intermediate layer is at least 20 micrometers, and a thickness of the DLC layer is at least 3 micrometers.

19. A method of forming a composite material comprising: applying a treated substrate layer onto a substrate; applying an adhesion layer onto the treated substrate layer; treating the treated substrate layer with a thermochemical diffusion process before applying the adhesion layer onto the treated substrate layer; applying an intermediate layer onto the adhesion layer; and applying a final diamond like carbon (DLC) layer on the intermediate layer.

20. The method of claim 19, further comprising lapping the treated substrate layer after treating the treated substrate layer with the thermochemical diffusion process and before applying the adhesion layer onto the treated substrate layer.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0016] The composite material (7) will be described with reference to the attached figures, which represent the scope thereof in a schematic and non-limiting form, as follows:

[0017] FIG. 1—Scheme of the layers of the composite material (7) in the embodiments of the present application;

[0018] FIG. 2—Pictures of the test specimens (A) and (B) of the chemical compatibility test from the embodiments of the present application;

[0019] FIG. 3—Plot of the coefficient of friction of the valves from the embodiments of the present application;

[0020] FIG. 4—Plot of the coefficient of friction of the valves from the embodiments of the present application;

[0021] FIG. 5—Plot of the sandless test under room temperature-cycling on the embodiments of the present application;

[0022] FIG. 6—Plot of the sandless test under high temperature-cycling on the embodiments of the present application;

[0023] FIG. 7—Plot of the sand test under room temperature-cycling on the embodiments of the present application;

[0024] FIG. 8—Plot of the sand test under high temperature-cycling on the embodiments of the present application;

[0025] FIG. 9—Picture of the upstream side of the gate after a thermal cycling sand test on the embodiments of the present application;

[0026] FIG. 10—Picture of the downstream side of the gate after a thermal cycling sand test on the embodiments of the present application;

[0027] FIG. 11—Picture of the upstream side of the seat after a thermal cycling sand test on the embodiments of the present application;

[0028] FIG. 12—Picture of the downstream side of the seat after a thermal cycling sand test on the embodiments of the present application.

DETAILED DESCRIPTION

[0029] As can be seen in FIG. 1, an example of the composite material (7) according to the present application may comprise a treated substrate (2), an adhesion layer (3), onto which an intermediate layer (4) is disposed, wherein a DLC layer (5) is disposed on said intermediate layer (4), all these layers being disposed on the surface of the substrate (1) of a gate valve (6). It should be appreciated that this disclosure is not limited to this configuration, and modifications to the composite material (7) are possible within the scope of this disclosure.

Treated Substrate (2)

[0030] The treated substrate (2) may be the outer surface of the substrate (1) composed of a metallic alloy with an austenitic structure, in one embodiment, the metallic alloy of the substrate (1) may be a nickel alloy. The thickness of the treated substrate (2) can be between 10 and 30 micrometers, the treated substrate (2) can be obtained by hardening, through a thermochemical diffusion treatment, the surface of the substrate (1) of a gate valve (6), wherein such hardening is preferably carried out by a process called Kolsterising, which is provided by the company BODYCOTE®. The Kolsterising process is a low-temperature thermochemical process that provides hardening as a result of the formation of an expanded austenite due to the addition of carbon and/or nitrogen, in such a way that the treated substrate hardens without compromising its corrosion resistance properties. Furthermore, other low-temperature diffusion treatment processes could be used to harden the treated substrate (2), such as the Balitherm thermal process by OERLIKON®; alternatively, mixing and friction process, such as Friction Stir Processing (FSP), could be used to harden the treated substrate (2).

[0031] In certain embodiments, after thermochemical treatment to obtain the treated substrate (2), a lapping post-process can alternatively be used to reduce the surface roughness of the treated substrate (2).

Adhesion Layer (3)

[0032] In certain embodiments, an adhesion layer (3) can be added to the treated substrate (2). The use of the adhesion layer (3) can facilitate the addition of other intermediate layers (4), which can be composed of metallic materials. The adhesion layer (3) can be a thin layer of approximately 0.5 micrometers, and composed of chromium, silicon, or other suitable material. In a preferred embodiment, the adhesion layer (3) is composed of chromium.

Intermediate Layer (4)

[0033] The intermediate layer (4) can be used in a composite material (7), e.g., a high hardness gradient between the DLC film (5) and the adhesion layer (3). That is, the intermediate layer (4) can provide a support for the DLC film (5) which typically has a brittle characteristic. Furthermore, the intermediate layer (4) has the characteristic of being an additional barrier against corrosion between the treated substrate (2) and the external environment.

[0034] In certain embodiments, the intermediate layer (4) can comprise tungsten carbide (WC). In certain embodiments, including when the intermediate layer (4) comprises WC, the intermediate layer can be deposited by a physical vapor deposition (PVD) process, preferably by a magnetron sputtering process. The intermediate layer (4) can, but not essentially, have a minimum thickness of 20 micrometers and comprise typical hardness in the range of 27 to 30 Gpa. However, the WC layer can comprise a typical hardness lower than the range of 27 to 30 GPa, and be less brittle, and this is possible by choosing another deposition process, or even by changing the parameters/conditions in the deposition process, such as the introduction of gases during the process (e.g., acetylene).

DLC Layer (5)

[0035] The outer layer of the composite material (7) can comprise a DLC layer (5) which is applied to the intermediate layer (4). The DLC layer (5) can be amorphous and characterized by having a low friction coefficient (0.05-0.2), preferably between 0.05 and 0.1, and higher hardness. In certain embodiments, DLC can be hydrogenated, with a hydrogen content of approximately 27%. Furthermore, the thickness of the DLC layer (5) can be at least 3 micrometers. It should be considered that the composition and configuration of the DLC layer (5) is not limited to the composition and configuration mentioned above. The DLC layer can comprise a typical hardness in the range of 22 to 25 Gpa.

[0036] In certain embodiments, the DLC layer (5) is deposited by a Chemical Vapor Deposition (CVD) process. In other embodiments, the DLC layer (5) can be deposited by processes such as Plasma-Enhanced Chemical Vapor Deposition (PECVD), or any other known deposition process that would be appreciated by a person skilled in the art.

[0037] In cases where the intermediate layer of WC is deposited by another deposition process, or wherein the PVD process is performed by changing parameters/conditions, the typical hardness of the intermediate layer (4) can be less hard and less brittle than the DLC layer (5). Likewise, the intermediate layer (4) can be less hard and more brittle than the adhesion layer (3) and the treated substrate (2).

Tests with the Composite Material

[0038] Composite material layers having characteristics similar to those described above were subjected to full-scale and specimen functional tests. The results of these tests are shown below. The tests were carried out in a closed loop system containing fluid with a given amount of sand (test set forth by standard/API 6AV1), wherein the closed-loop test subjects the composite material to distinct and aggressive conditions—Chemical compatibility test.

[0039] As can be seen in FIG. 2, test specimens (A) and (B) were subjected to immersion tests in hydrochloric acid (HCl) and hydraulic oil at a high temperature (150° C.) and for a period of 30 days, following the NACE/ISO15156 standard (level V test conditions for 30 days). In addition, test specimens (A) and (B) were subjected to assays under the pressure and temperature action (CO.sub.2 and H.sub.2S, at 150° C.), and the composite material withstood all the tests mentioned above.

Assessing the Coefficient of Friction in the Valves

[0040] The coefficient of friction was measured directly in the composite material (7) in the valve by assessing the actuating forces in different actuating cycles. FIGS. 3 and 4 are the actuation curves (axial force against time) for the typical solution used by industry (WC coating added with cobalt (Co) by thermal spray) and the present application comprising DLC. The coefficient of friction for the solution having WC—Co was 0.12, while the DLC showed a value much lower than 0.07.

Closed-Loop Testing with Sand-Containing Fluid Associated with Room Temperature and High Temperature Cycling

[0041] A cycling test was performed on the composite material (7), but the test set forth by API 6AV1 (sand slurry test) was modified to incorporate cycling before and after the sand test (extremely aggressive), by which the sealing capacity of the gate valve is checked in cycling performed at room temperature and 177° C. FIGS. 5, 6, 7 and 8 are the curves from the tests performed, wherein FIG. 5 illustrates the sandless test in which 40 cycles are performed at a pressure of 10,000 PSI and at room temperature; FIG. 6 illustrates the sandless test in which 40 cycles are performed at a pressure of 10,000 PSI and at high temperature (177° C.); FIG. 7 illustrates the sand test in which 40 cycles are performed at a pressure of 10,000 PSI and at room temperature and FIG. 8 illustrates the sand test in which 40 cycles are performed at a pressure of 10,000 PSI and at high temperature (177° C.).

[0042] As can be seen in FIGS. 5-8, the actuating curves in each of the steps demonstrate that the actuation curve (also called the valve signature) has not changed significantly. Furthermore, the valve sealed gas after all the steps described above, demonstrating the ability to maintain its functionality even after being subjected to the test conditions.

[0043] It is important to mention that, in addition to the evaluation of the “valve signature”, the analysis of the parts after testing showed that even in the regions where the DLC coating (5) was removed from, the treated substrate was not exposed.

[0044] FIGS. 9 and 10 are pictures of the gates, and FIGS. 11 and 12 are pictures of the seats; these pictures showing the gates and seats after the tests performed to demonstrate the strength/durability of the parts coated by the composite material (7).

[0045] As will be appreciated by a person skilled in the art, the present application affords the possibility of: [0046] decreasing the coefficient of friction using DLC under harsh conditions, such as abrasion, erosion and aggressive corrosive environment, and under high contact stresses; and [0047] increasing durability under typical environmental conditions of oil exploration and production operations when compared to the current solution employed by the industry.