PART INTENDED TO BE IMMERSE IN A BODY OF WATER

Abstract

The invention relates to a part (1), in particular for a periscopic installation, intended to be immersed in a body of water, the part (1) comprising a metal body (2) having a surface (2a) and a coating (6) arranged on the surface (2a), characterized in that the surface (2a) has an arithmetic mean roughness Ra less than or equal to 0.1 µm, and in that the coating (6) comprises a hydrogenated DLC layer (6a). Abstract figure: 2

Description

Title of the invention: PART INTENDED TO BE IMMERSE IN A BODY OF WATER Technical field of the invention

[0001] The invention relates to the technical field of parts intended to be immersed in a body of water. The invention relates in particular to parts for periscopic installations. Technical background

[0002] Submarines are submerged in a body of water, for example at sea. As part of their missions, submarines must ensure the observation of objects placed on the surface of the water for example.

[0003] For this purpose, they are typically equipped with a periscopic installation allowing the optical observation of objects at a distance without making the submarine visible.

[0004] A periscope installation typically comprises a metal tube and at least one mirror mounted at each end of the tube. The periscope installation also comprises parts which ensure the mounting of the tube in the submarine for example.

[0005] These parts typically comprise a metal body. As they reside in a marine environment, the parts are quickly subject to strong marine corrosion. It is therefore important to improve their corrosion resistance in order to guarantee their integrity over time.

[0006] For this purpose, it is known to deposit on the metal body a coating of nickel and phosphorus by a high phosphorus chemical nickel treatment for example. The thickness of the coating is generally 80 μm. Although it considerably improves the corrosion resistance of the part, such a coating is not entirely satisfactory.

[0007] Indeed, the significant thickness of the coating deposited by the chemical nickel process generates internal stresses in the coating. These internal stresses result in crazing which represents a network of cracks and fissures appearing on the surface of the coating. Such crazing considerably reduces the corrosion resistance of the part and it is therefore necessary to remove the coating from the metal body and then deposit a new coating. The manufacturing time of the part is therefore particularly long.

[0008] In addition, the part generally cooperates with a seal to limit leaks in the installation. It has been found that friction between the seal and the coating leads to premature wear of the coating and of the seal. This reduces the longevity of the part and the seal, which must be replaced regularly to ensure the installation is watertight.

[0009] In this context, there is a need to provide a part, in particular for a periscopic installation, intended to be immersed in a body of water, which is resistant to marine corrosion, to wear and whose manufacturing time is reduced. Summary of the invention

[0010] For this purpose, the invention proposes a part, in particular for a periscopic installation, intended to be immersed in a body of water, the part comprising a metal body having a surface and a coating arranged on the surface.

[0011] The part is remarkable in that the surface has an arithmetic mean roughness Ra less than or equal to 0.1 pm, and in that the coating comprises a hydrogenated DLC layer.

[0012] The coating according to the invention comprises a hydrogenated (ac:H) DLC (Diamond Like Carbon) layer which has the advantage of not causing crazing. The method for manufacturing the part therefore comprises a single step of depositing the coating which makes it possible to reduce the manufacturing time of the part unlike the coatings of the prior art which require several deposits to arrive at a coating without crazing.

[0013] Furthermore, such a layer has good tribological properties. Thanks to these new tribological properties, friction between the DLC layer and the seals is limited. The invention therefore makes it possible to reduce premature wear of the coating and the seals with which it can cooperate. Thanks to the invention, the longevity of the part is increased.

[0014] Furthermore, according to the invention, the surface of the metal body has an arithmetic mean roughness Ra less than or equal to 0.1 pm.

[0015] It has been found that beyond this threshold arithmetic mean roughness value, the intrinsic resistance to marine corrosion of the metal body was significantly degraded despite the presence of the hydrogenated DLC layer. Such an arithmetic mean roughness value of the metal body in combination with the hydrogenated DLC layer therefore makes it possible to limit the marine corrosion of the part.

[0016] The invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another:

[0017] - the arithmetic mean roughness Ra is less than or equal to 0.09 pm,

[0018] - the surface has a total roughness Rt less than or equal to 1.6 pm, preferably less than or equal to 1.4 pm,

[0019] - the surface has an average roughness Rz less than or equal to 1 pm, preferably less than or equal to 0.9 pm,

[0020] - the DLC layer has a thickness of less than 10 μm, preferably less than 5 pm, even more preferably between 1 pm and 5 pm,

[0021] - the DLC layer is doped with silicon oxide,

[0022] - the coating comprises a matting layer arranged on at least a portion of the DLC layer,

[0023] - the mattifying layer comprises a paint,

[0024] - the DLC layer has a first part and a second part, the layer mattifying being arranged on the first part and the second part being devoid of mattifying layer and intended to cooperate with a seal,

[0025] - the metal body is made of stainless steel,

[0026] - the part is a part of revolution.

[0027] The invention also relates to a method of manufacturing a part according to any one of the preceding characteristics, and comprising the following steps:

[0028] a) providing a metallic body having a surface,

[0029] b) forming a coating on the surface.

[0030] The method is remarkable in that in step a) the surface has an arithmetic mean roughness Ra less than or equal to 0.1 pm, and in that step b) comprises a sub-step b1) of depositing a hydrogenated DLC layer. Brief description of the figures

[0031] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

[0032] [Fig.l] is an axial sectional view of an assembly to which the invention can be applied;

[0033] [Fig.2] is an axial sectional view of a part according to the invention equipping the assembly of [Fig.l];

[0034] [Fig. 3] is an axial sectional view of a part according to a particular embodiment of the invention and cooperating with a joint of the assembly of [Fig. 1];

[0035] [Fig.4] is a microscope image of a sample of a part according to the invention;

[0036] [Fig.5] is a block diagram of a method of manufacturing the part according to the invention. Detailed description of the invention

[0037] Submarines are typically equipped with a periscopic installation for observing objects at a distance.

[0038] The periscopic installation (not shown) is therefore intended to be immersed in a body of water. The periscopic installation is intended to reside in a highly corrosive environment.

[0039] Such a periscopic installation typically comprises a metal tube comprising at each of its ends at least one mirror allowing the observation of objects at a distance.

[0040] [Fig.l] represents for example an assembly E comprising a part 1 equipping such a periscopic installation. The part 1 has for example an axis of revolution X.

[0041] The part 1 comprises a body 2. The body 2 is metallic. Advantageously, the metallic material of the body 2 is chosen from stainless steels. The stainless steel is for example a martensitic stainless steel such as the APX4 steel grade. Such a metallic material makes it possible to improve the resistance to marine corrosion of the part 1.

[0042] The body 2 also has a surface 2a. The surface 2a has an arithmetic mean roughness Ra less than or equal to 0.1 pm. Preferably, the arithmetic mean roughness Ra is less than or equal to 0.09 pm, and even more preferably less than or equal to 0.05 pm.

[0043] The arithmetic mean roughness Ra is defined in the ISO4287:1997 standard. It is understood as the arithmetic mean of the absolute values ​​of the ordinates of the surface roughness profile within a base length of the profile.

[0044] Advantageously, the surface 2a has a total roughness Rt less than or equal to 1.6 pm, preferably less than or equal to 1.4 pm.

[0045] The total roughness Rt is defined in ISO4287:1997. It is understood as the sum of the largest of the profile protrusion heights and the largest of the profile trough depths, within an evaluation length. The evaluation length is 4 mm as determined in ISO 4288:1996.

[0046] Advantageously, the surface 2a has an average roughness Rz less than or equal to 1 pm, preferably less than or equal to 0.9 pm.

[0047] The average roughness Rz is defined in the ISO4287:1997 standard. It is understood as the sum of the largest of the profile protrusion heights and the largest of the profile trough depths within the base length.

[0048] The arithmetic mean roughness Ra, the average roughness Rz and the total roughness Rt are measured using a roughness meter such as the Mitutoyo® SJ210 roughness meter.

[0049] Furthermore, with reference to [Fig.2], the part 1 comprises a coating 6 arranged on the surface 2a of the body 2. According to the invention, the coating 6 comprises a hydrogenated DLC layer 6a (ac:H). Preferably, the DLC layer 6a is arranged on the entire surface 2a. The DLC layer 6a has a thickness of less than 10 pm, preferably less than 5 pm, and even more preferably between 1 pm and 5 pm, in particular between 1 pm and 3 pm.

[0050] Preferably, the DLC layer 6a has an arithmetic mean roughness Ra less than or equal to 0.2 pm, and even more preferably less than or equal to 0.18 pm.

[0051] Preferably, the DLC layer 6a has a total roughness Rt less than or equal to 2.5 pm and even more preferably less than or equal to 2 pm.

[0052] Preferably, the DLC layer 6a has an average roughness Rz less than or equal to 2 pm, and even more preferably less than or equal to 1.8 pm.

[0053] Such a surface state of the DLC layer 6a makes it possible to further improve the resistance to marine corrosion of the part 1.

[0054] Preferably, the DLC layer 6a has a hydrogen content of between 15% and 50%, preferably between 15% and 35%.

[0055] Preferably, the DLC layer 6a is doped with silicon oxide (SiO). The material of the DLC layer 6a is for example BALINIT® Dylyn 180 from the company Oerlikon Balzers.

[0056] Advantageously, the coating 6 comprises a sub-layer 6c arranged between the surface 2a and the DLC layer 6a. The sub-layer 6c advantageously comprises titanium (Ti) or chromium nitride (CrN). It makes it possible to promote the attachment of the DLC layer 6a to the metal body 2.

[0057] Advantageously, and with reference to [Fig. 3], the coating 6 comprises a matting layer 6b arranged on at least a portion of the DLC layer 6a. The DLC layer 6a is arranged between the metal body 2 and the matting layer 6b. The matting layer 6b is for example arranged on a first portion of the DLC layer 6a and a second portion of the DLC layer 6a is devoid of the matting layer 6b. The matting layer 6b makes it possible to limit the visibility of the part 1 to ensure its discretion.

[0058] The mattifying layer 6b preferably comprises a paint. The thickness of the mattifying layer 6b is advantageously between 100 μm and 300 μm, preferably between 200 μm and 300 μm, for example 250 μm.

[0059] The presence of silicon oxide in the DLC layer 6a makes it possible to increase the chemical affinity between the DLC layer 6a and the matting layer 6b.

[0060] The assembly E further comprises a member 7 cooperating for example with the part 1. The member 7 is for example metallic. It is for example annular and centered on the axis of revolution X. It is for example arranged around the part 1. The member 7 carries a seal 8. The member 7 has for example a groove in which the seal 8 is arranged.

[0061] The seal 8 is located between the part 1 and the member 7. The seal 8 is preferably arranged around the second part of the DLC layer 6a devoid of the matting layer 6b. The seal 8 is for example annular. The seal 8 is for example made of polymeric material such as an elastomer chosen for example from nitrile rubbers (NBR for “nitrile butadiene rubber” in English).

[0062] The part 1 is for example fixed and / or mobile and the member 7 is for example fixed and / or mobile. The member 7 and / or the part 1 are for example mobile in rotation and / or in translation.

[0063] The assembly 1 is a jack, for example a hydraulic jack. The part 1 is cylindrical and centered on the axis of revolution X. The body 2 of the part 1 comprises, for example, a rod 3 extending along and around the axis of revolution X and a piston 4 arranged on a longitudinal end of the rod 3. The seal 8 is arranged around the rod 3. The surface 2a of the body 2 is the external surface of the body 2.

[0064] The member 7 is for example a cylindrical envelope arranged around the part 1 and centered on the axis of revolution X.

[0065] According to this example, the part 1 is movable in translation along the axis of revolution X and the member 7 is fixed.

[0066] According to another example not shown, the part 1 is arranged around the member 7. The surface 2a of the body 2 is then the internal surface of the body 2 of the part 1.

[0067] The DLC layer 6a has the advantage of not causing crazing of the coating 6. Indeed, it is possible to deposit very small thicknesses of DLC which makes it possible to limit the internal stresses in the DLC layer 6a.

[0068] Furthermore, such a layer has good tribological properties. Thanks to these new tribological properties, it is possible to limit the friction between the DLC layer 6a and the seal 8 and therefore to reduce the premature wear of the coating 6 and the seal 8. Thanks to the invention, the longevity of the part 1 is increased.

[0069] Furthermore, thanks to the arithmetic mean roughness Ra of the external surface 2a in combination with the DLC layer 6a, it is possible to limit the marine corrosion of the part 1.

[0070] Finally, very advantageously, the silicon oxide doping of the DLC layer 6a makes it possible to increase the adhesion of the DLC layer 6a with the matting layer 6b. It is therefore possible to mattify the part 1 using a paint to guarantee the discretion of the part 1 during underwater operations.

[0071] A method of manufacturing part 1 will now be described with reference to [Fig.5].

[0072] The method comprises the following steps:

[0073] a) providing the metal body 2,

[0074] b) forming the coating 6 on the surface 2a of the metal body 2.

[0075] Step b) includes the following sub-steps carried out in chronological order:

[0076] - optionally a sub-step bO) of depositing the sub-layer 6c. The sub-layer 6c is for example deposited by physical vapor deposition (PVD);

[0077] - a sub-step bl) of depositing the hydrogenated DLC layer 6a. The DLC layer 6a hydrogenated is for example deposited by plasma-enhanced chemical vapor deposition (PACVD);

[0078] -optionally a sub-step b2) of depositing the mattifying layer 6b. Examples

[0079] Example 1: corrosion test

[0080] Three circular test pieces (1, 2, 3) of 85 mm diameter and 6 mm thickness made of APX4 grade stainless steel were produced. The arithmetic mean roughness Ra of the surface of each test piece is less than 0.1 pm.

[0081] On test piece 1 a layer of tungsten carbide-doped carbon (WC / C) marketed under the name BALINIT® C by the company Balzers was deposited on the surface of the test piece by physical vapor deposition (PVD), in particular by arc evaporation. The thickness of the layer is 2 pm.

[0082] On specimens 2 to 3 a hydrogenated DLC layer (ac:H) with a thickness of 1.85 mm was deposited on the surface of the specimens by plasma-assisted chemical vapor deposition (PACVD).

[0083] These test pieces were subjected to a salt spray resistance test for 1440 hours according to standard NF EN ISO 9227.

[0084] The results are presented in Table 1.

[0085] [Tables 1] Test specimens Hydrogenated DLC layer (ac:H) Corrosion resistance 1 - No 2 + Yes 3 + Yes

[0086] Test pieces 2 and 3 show no degradation after 1440 hours in salt spray.

[0087] On the other hand, test piece 1 shows corrosion pitting after 120 hours.

[0088] These results show that the hydrogenated DLC layer gives the part good resistance to marine corrosion.

[0089] Example 2: roughness measurement and corrosion test

[0090] Rings comprising a metallic body having an arithmetic mean roughness Ra as indicated in the table below and a coating comprising a hydrogenated DLC layer were subjected to a wear test for 6000 hours followed by a salt spray resistance test according to standard NF EN ISO 9227 for 768 hours.

[0091] The results are presented in Table 2.

[0092] [Tables2] Rings Ra (pm) Corrosion resistance 1 0.0445 Yes 2 0.07 Yes 3 1.2 No

[0093] The results show that the rings having an arithmetic mean roughness Ra according to the invention are resistant to marine corrosion unlike the rings having an arithmetic mean roughness Ra beyond the threshold value established by the invention.

[0094] Example 3: adhesion test

[0095] Circular specimens of 85 mm diameter and 6 mm thickness in APX4 grade stainless steel were produced.

[0096] A hydrogenated DLC layer (ac:H) doped with silicon oxide (BALINIT® Dylyn 180) with a thickness of 1.85 mm was deposited on the test pieces.

[0097] A layer of paint was deposited on the DLC layer.

[0098] These test pieces were subjected to a salt spray resistance test for 1440 hours according to standard NF EN ISO 9227.

[0099] The adhesion of the paint layer to the DLC layer was measured by tensile test according to standard NF EN ISO 4624 at Oh (tO) and after 1440 hours.

[0100] The results show that the adhesion strength between the paint layer and the DLC layer at t0 is 12 MPa and after 1440 h 10 MPa.

[0101] The specifications generally impose an adhesion strength of 4 MPa. In conclusion, silicon oxide makes it possible to significantly increase the adhesion between the paint layer and the DLC layer.

[0102] Example 4: microscope observation

[0103] A sample of part 1 in APX4 grade stainless steel was produced. A titanium underlayer was deposited and then a hydrogenated DLC layer doped with silicon oxide with a thickness of 2.2 μm was deposited on the sample (BALINIT® Dylyn 180 from Oerlikon Balzers). The sample was cut using a micro-cutting machine.

[0104] To facilitate observation of the DLC layer, a layer of aluminum was deposited on the cut sample.

[0105] The micrographic sections are observed under a FEG Jeol JSM-7100F microscope with a magnification of x5000.

[0106] A snapshot of the microscope observation of the sample is shown in [Fig.4],

[0107] The distribution of the different main chemical elements forming each layer is observed. Iron makes up the metallic body 2, titanium Ti makes up the sub-layer 6c, carbon C and silicon Si form the hydrogenated DLC layer 6a doped with silicon oxide. It is observed that the silicon Si elements form a layer on the upper surface of the carbon C elements.

[0108] The results show that the hydrogenated DLC 6a layer doped with silicon oxide makes it possible to promote the chemical affinity between the DLC 6a layer and the matting layer 6b thanks to the silicon Si elements. This makes it possible to increase the adhesion between the DLC 6a layer and the matting layer 6b.

Claims

Claims

1. Periscopic installation comprising a part (1), intended to be immersed in a body of water, the part (1) comprising a metallic body (2) having a surface (2a) and a coating (6) arranged on the surface (2a), characterized in that the surface (2a) has an arithmetic mean roughness Ra less than or equal to 0.1 pm, and in that the coating (6) comprises a hydrogenated DLC layer (6a).

2. Periscopic installation according to the preceding claim, characterized in that the arithmetic mean roughness Ra is less than or equal to 0.09 pm.

3. Periscopic installation according to any one of the preceding claims, characterized in that the surface (2a) has a total roughness Rt less than or equal to 1.6 pm, preferably less than or equal to 1.4 pm.

4. Periscopic installation according to any one of the preceding claims, characterized in that the surface (2a) has an average roughness Rz less than or equal to 1 pm, preferably less than or equal to 0.9 pm.

5. Periscopic installation according to any one of the preceding claims, characterized in that the DLC layer (6a) has a thickness of less than 10 pm, preferably less than 5 pm, even more preferably between 1 pm and 5 pm.

6. Periscopic installation according to any one of the preceding claims, characterized in that the DLC layer (6a) is doped with silicon oxide.

7. Periscopic installation according to the preceding claim, characterized in that the coating (6) comprises a matting layer (6b) arranged on at least part of the DLC layer (6a).

8. Periscopic installation according to the preceding claim, characterized in that the matting layer (6b) comprises a paint.

9. Periscopic installation according to one of claims 7 or 8, characterized in that the DLC layer (6a) has a first part and a second part, the matting layer (6b) being arranged on the first part and the second part being devoid of a matting layer (6b) and intended to cooperate with a sealing joint (8).

10. Periscopic installation according to any one of the preceding claims, characterized in that the metal body (2) is made of stainless steel.

11. Periscopic installation according to any one of the preceding claims, characterized in that the part (1) is a part of revolution.

12. A method of manufacturing a periscopic installation according to any one of the preceding claims, the method comprising the following steps: a) providing a metallic body (2) having a surface (2a), b) forming a coating (6) on the surface (2a), characterized in that in step a) the surface (2a) has an arithmetic mean roughness Ra less than or equal to 0.1 pm, and in that step b) comprises a sub-step bl) of depositing a hydrogenated DLC layer (6a).

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