JP5441488B2 - Ship propeller - Google Patents

Description

  The present invention relates to a marine propeller that generates a propulsive force in a hull, and more particularly, to a marine propeller that is imparted with cavitation erosion resistance and antifouling properties against marine organisms by forming a protective film.

  In a propeller for a ship used for a propulsion device for a ship, erosion (erosion) due to cavitation may occur with the recent increase in size and speed of a ship. The ship's propulsion efficiency has been improved by technological development of the hull, but the problem is that the ship's propulsion efficiency cannot be raised to a sufficient level due to the cavitation and erosion of the ship's propeller. Yes. In order to solve this problem, it has been studied to improve the structure of the marine propeller to give the marine propeller anti-cavitation and erosion, but such an improvement has reached the limit. Currently.

  Therefore, as another method for imparting cavitation erosion resistance to a marine propeller, it is conceivable to form a protective film having excellent cavitation erosion resistance on the surface of the marine propeller. As a technique applicable in this case, for example, Patent Document 1 and Patent Document 2 can be cited. In Patent Document 1, cavitation resistance of the surface of the member is formed by forming a built-up layer of a high-C, high-Si content weld metal powder on the surface of the member of various devices used in an environment such as a liquid by plasma welding.・ Improves erosion. Moreover, in patent document 2, in the hydraulic machine provided with a water turbine runner or an impeller, austenitic stainless steel is build-up welded to a part subjected to an impact by flowing water to impart cavitation erosion resistance to the part.

  On the other hand, marine organisms such as shellfish and barnacles adhere to the ship propeller due to long-term operation of the ship, and when this grows and enlarges, it adversely affects the speed and fuel efficiency of the ship. As a countermeasure, for example, in Patent Document 3, a propeller is formed of a conductive metal, a porous chromium base layer is electrodeposited on the surface thereof, and the surface of the chromium base layer is covered with a fluororesin, whereby a marine propeller is provided. It is disclosed that marine organisms such as shellfish are less likely to adhere. Furthermore, in Patent Document 4, as a method for preventing the seawater contact structure from being stained, the surface of the seawater contact structure is coated with a corrosion-resistant metal to form a cathode, and a direct current is passed between the anode and the anode disposed opposite thereto. Then, after an electrocoating layer is formed on the surface and marine organisms are attached, a reverse current is passed between the electrodes to dissolve and remove the electrocoating layer to remove marine organisms such as shellfish.

JP-A-6-170584 JP 2001-107833 A JP-A-8-207890 JP 2002-317282 A

  In the said patent document 1 and the patent document 2, it is only about the point regarding cavitation erosion resistance, and in the said patent document 3 and patent document 4, it is made hard to adhere marine organisms to the propeller for ships, respectively, and seawater contact structure It is only the point regarding the antifouling method of things. That is, none of the protective coatings described in these patent documents can be a marine propeller that has both cavitation erosion resistance and antifouling properties against marine organisms. In particular, in the marine propeller of Patent Document 3, it is expected that the fluororesin on the surface will be peeled off by cavitation, so even the antifouling property against marine organisms is not sufficient. Furthermore, in Patent Document 3, it is necessary to form not only a metal layer but also a resin layer. In Patent Document 4, since a work of flowing a reverse current between the electrodes is required after marine organisms are attached, Patent Document 3 3 and Patent Document 4 have a problem in that costs for antifouling measures against marine organisms increase.

  Therefore, in view of the above-mentioned problems of the prior art, the present invention has both cavitation erosion resistance and antifouling properties against marine organisms, and at the same time, the cost for antifouling measures against marine organisms is suppressed. The purpose is to provide a propeller.

In order to achieve the above object, the following technical measures were taken.
That is, the marine propeller of the present invention is a marine propeller in which a protective coating is formed on the outer surface of the propeller body for generating a propulsive force for propelling the hull, and the protective coating is Ni: 3% by mass or less. Co: Alloy containing Cr: 25-35% by mass , W: 4-20% by mass , Fe: 3% by mass or less, C: 4% by mass or less, and the balance: Co and inevitable impurities. It is characterized by being formed.

With the marine propeller of the present invention, Ni: 3% by mass or less, Cr: 25-35% by mass , W: 4-20% by mass , Fe: 3% by mass or less, C: By forming a protective film having a composition comprising 4% by mass or less and the balance: Co and unavoidable impurities, both cavitation and erosion resistance and antifouling properties against marine organisms can be obtained from the characteristics of these compositions. Properties can be imparted to the marine propeller. Furthermore, since the resin layer is unnecessary and the work of removing the film by applying a reverse current between the electrodes after the marine organisms are attached is unnecessary, the cost for antifouling measures against marine organisms can be reduced. .

  Various methods can be adopted as a method of forming the protective film on the outer surface of the propeller body. For example, a thermal spraying method may be mentioned, and among these thermal spraying methods, the protective coating is preferably formed by a high-speed flame spraying method or a low pressure plasma spraying method. By adopting these thermal spraying methods, the cavitation erosion resistance and the antifouling property against marine organisms of the protective film having the above composition can be more effectively expressed.

  The thickness of the protective coating formed on the outer surface of the propeller body is appropriately changed according to the vessel in which the marine propeller is used and the environment in which the vessel is operated. It is preferable that it is 0.1-1.0 mm. By using a protective film with this thickness, it is possible to develop excellent cavitation and erosion resistance and to reduce manufacturing costs.

  The surface of the protective film preferably has a Vickers hardness of 200 or more. By using a protective film of this hardness, cavitation erosion resistance and antifouling properties against marine organisms can be further improved.

  As described above, according to the present invention, by forming a protective coating made of a Co-based alloy on the outer surface of the propeller body, it has both cavitation erosion resistance and antifouling properties against marine organisms. be able to. Furthermore, since the resin layer is unnecessary and the work of removing the film together with marine organisms is unnecessary, the cost for antifouling measures against marine organisms can be reduced.

1 is a perspective view of a marine propeller according to an embodiment of the present invention and an enlarged cross-sectional view of a surface layer of a propeller body. It is the schematic of an ultrasonic vibration type cavitation erosion test apparatus. It is a bar graph showing the test result of a cavitation erosion resistance test. It is a bar graph showing the test result of an antifouling property test. It is the surface photograph of the test piece (with a film | membrane) after being immersed in the sea. It is a cross-sectional image (A line cross-sectional image of FIG. 5) of a test piece (with a coating). It is a cross-sectional image (B line cross-sectional image of FIG. 5) of a test piece (with a coating). It is a cross-sectional-analysis image of the test piece (without a film | membrane) after being immersed in the sea. It is the surface photograph after removing the barnacle adhering to the test piece (the film is not present).

As a result of intensive studies by the present inventors, the protective coating on the outer surface of the propeller body of the marine propeller is a thermal spray coating formed of a Co-based alloy, thereby preventing not only cavitation and erosion resistance but also marine organisms. The present inventors have found that it is possible to provide soiling properties and have completed the present invention.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a marine propeller 1 according to an embodiment of the present invention and an enlarged sectional view of a surface layer 2 thereof. The marine propeller 1 mainly includes a shaft 3 connected to a propulsion device for a hull (not shown) and a wing portion 4 extending in the radial direction from the outer periphery 3a of the shaft 3. As shown in the enlarged cross-sectional view of the surface layer 2 in the figure, a protective film 6 is formed on the outer surface 5 of the shaft 3 (propeller body) and the wing part 4 (propeller body) of the marine propeller 1.

The protective film 6 is formed on the outer surface 5 of the propeller bodies 3 and 4 with Ni: 3 mass %, Cr: 30 mass %, W: 4.5 mass %, Fe: 3 mass %, and C: 1.1 mass %. The remainder is a thermal spray coating formed by thermal spraying a powder of a Co-based alloy having a composition consisting of Co and inevitable impurities. Accordingly, the sprayed coating 6 is made of a Co-based alloy having the composition. As a composition of the said thermal spray coating 6, Ni: 3 mass % or less, Cr: 25-35 mass %, W: 4-20 mass %, Fe: 3 mass % or less, C: 4 mass % or less, The remainder : Co and unavoidable impurities are preferable. By adopting such a composition, the thermal spray coating 6 is less likely to be eroded by marine organisms, the adhesion between the thermal spray coating 6 and marine organisms is reduced, and the antifouling property against marine organisms can be improved. Furthermore, cavitation erosion resistance can be improved.

The reason why the above ranges are set for the respective components is as follows. When Ni exceeds 3% by mass, the cavitation and erosion resistance cannot be sufficiently improved. As for Cr, if it is less than 25% by mass , the corrosion resistance is lowered, and if it exceeds 35% by mass , the coating becomes brittle. When W is less than 4% by mass , the required hardness cannot be obtained, and when it exceeds 20% by mass , the film becomes brittle. When Fe exceeds 3% by mass , rust is likely to occur. About C, if it exceeds 4% by mass , the film becomes brittle.

  Further, as a method of forming the protective film 6, the cavitation erosion resistance can be remarkably improved by adopting a thermal spraying method as in this embodiment. Examples of the spraying method include various methods such as an atmospheric plasma spraying method, a low-pressure plasma spraying method, a high-speed flame spraying method, and a flame spraying method, and a high-speed flame spraying method or a low-pressure plasma spraying method is particularly preferable. By adopting the high-speed flame spraying method, the adhesion between the thermal spray coating 6 and the outer surface 5 of the propeller body 3, 4 is increased, and the dense structure of the thermal spray coating 6 is obtained, resulting in high durability. It can be set as the firm and strong sprayed coating 6. In addition, by adopting the low pressure plasma spraying method, the bonding force between the metal particles constituting the thermal spray coating 6 is strengthened, and the dense structure of the thermal spray coating 6 is obtained, so that it has high durability. And it can be set as the strong protective film 6. FIG.

  The thickness of the thermal spray coating 6 is preferably 0.1 to 1.0 mm. The reason is that if it is less than 0.1 mm, the cavitation and erosion resistance is insufficient, and if it exceeds 1.0 mm, it takes a long time to form a film, resulting in an increase in manufacturing cost and exceeding 1.0 mm. This is because no significant improvement in the properties with respect to thickness (anti-cavitation / erosion resistance, antifouling properties against marine organisms) is observed.

  Moreover, it is preferable that the hardness of the surface 6a of the sprayed coating 6 is 200 or more in terms of Vickers hardness. If the hardness of the surface 6a is set to 200 or more in terms of Vickers hardness, the sprayed coating 6 having the following effects can be obtained. As a first effect, since marine organisms are less likely to erode from the surface 6a to the inside, adhesion between marine organisms and the thermal spray coating 6 is reduced. Since the adhesion between the marine organisms and the thermal spray coating 6 is reduced, even if marine organisms are apparently attached to the surface 6a of the thermal spray coating 6, the water propagator 1 rotates from the surface 6a due to the water flow or the like. Marine organisms can be easily detached. Thereby, the outstanding antifouling property can be exhibited. As a second effect, even if cavitation occurs in the propeller bodies 3 and 4, it is possible to prevent the hardness of the surface 6 a of the thermal spray coating 6 from affecting the outer surface 5 of the propeller bodies 3 and 4. Thereby, the outstanding cavitation erosion resistance can be exhibited.

  Furthermore, since the resin layer required in the prior art is unnecessary in this embodiment, and the work of removing the film by applying a reverse current between the electrodes after the marine organisms are attached is unnecessary. Costs for antifouling measures against living organisms can be reduced.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

A test piece with a sprayed coating was prepared, and a cavitation / erosion resistance test and an antifouling test against marine organisms were conducted.
(Cavitation and erosion resistance test)
The following test piece is prepared using a nickel / aluminum bronze casting (CAC703), which is often used as a material for marine propellers, as a base material. The cavitation / erosion resistance test was conducted after mounting. In addition, the ultrasonic vibration type cavitation erosion test apparatus manufactured the thing based on the ASTMG-32 standard in-house. This ultrasonic vibration type cavitation erosion test apparatus 10 is provided at an ultrasonic transducer 11 for generating vibration at an ultrasonic frequency and vibrating a test piece up and down, and below the ultrasonic transducer 11. The test piece 12 includes a horn portion 13 attached to the lower end, and a cooling water tank 14 for cooling the horn portion 13. A test liquid tank (not shown) provided in the cooling water tank 14 stores a test liquid 15, and the test piece 12 is immersed in the test liquid 15 in the state where the test piece 12 is immersed in the ultrasonic transducer 11. And cavitation is generated on the surface of the test piece 12.

  The test conditions in the ultrasonic vibration type cavitation erosion test apparatus 10 are as follows: maximum value of ultrasonic oscillation output: 1.2 kW, vibration frequency: 19.5 kHz, vibration amplitude: 50 μm, 60 μm, 70 μm, test solution temperature: 25 ± 0 .5 ° C., test time: 6 hours, and cavitation erosion resistance was evaluated by erosion speed (weight of test piece decreased per unit time).

[Example]
Example 1 A 0.5 mm Co-based alloy film was formed on a substrate by low pressure plasma spraying (VPS). The composition of the Co-based alloy was the composition of the above embodiment.
(Example 2) A 0.5 mm Co-based alloy film was formed on a substrate by high-speed flame spraying (HVOF). The composition of the Co-based alloy was the composition of the above embodiment.
(Example 3) A 0.5-mm Co-based alloy film was formed on a substrate by atmospheric plasma spraying (APS). The composition of the Co-based alloy was the composition of the above embodiment.
[Comparative example]
(Comparative Example 1) A film was not formed on the substrate.
(Comparative Example 2) A 0.5 mm Al ₂ O ₃ (alumina) film was formed on a substrate by an atmospheric plasma spraying method (APS).
(Comparative Example 3) A 0.5 mm CrC (chromium carbide) film was formed on a substrate by high-speed flame spraying (HVOF).
(Comparative Example 4) A 0.5 mm WC (tungsten carbide) film was formed on a substrate by high-speed flame spraying (HVOF).

A bar graph of the test results is shown in FIG. In addition, the numerical value of each Example and each comparative example is as follows.
Example 1: 0.01 mg / min, Example 2: 0.10 mg / min, Example 3: 0.27 mg / min, Comparative Example 1: 0.14 mg / min, Comparative Example 2: 0.53 mg / min, Comparative Example 3: 0.26 mg / min, Comparative Example 4: 0.22 mg / min.
From the above test results, it can be seen that Example 1 and Example 2 are superior to Comparative Example 2, Comparative Example 3, and Comparative Example 4 including Comparative Example 1 (base material) in terms of cavitation and erosion resistance. From this, it is understood that excellent cavitation and erosion resistance is imparted to the marine propeller by forming the Co-based alloy film by the low pressure plasma spraying method and the high-speed flame spraying method.

(Anti-fouling test for marine organisms)
The following test pieces were prepared using the above-described nickel / aluminum bronze casting (CAC703) as a base material, and immersed in the sea for 2 months to conduct antifouling tests against marine organisms. Antifouling properties against marine organisms were evaluated by the number of barnacles (marine organisms) attached.

[Example]
Example 1 A 0.5 mm Co-based alloy film was formed on a substrate by high-speed flame spraying (HVOF). The composition of the Co-based alloy was the composition of the above embodiment.
[Comparative example]
(Comparative Example 1) A 0.5 mm Al ₂ O ₃ (alumina) film was formed on a substrate by atmospheric plasma spraying (APS).
(Comparative Example 2) A 0.5 mm CrC (chromium carbide) film was formed on a substrate by high-speed flame spraying (HVOF).
(Comparative Example 3) A 0.5 mm WC (tungsten carbide) film was formed on a substrate by high-speed flame spraying (HVOF).

A bar graph of the test results is shown in FIG. In the bar graph, barnacle size range groups (group a, 5 mm to less than 8 mm, group b, 8 mm to less than 11 mm, group c, 11 mm or more) are shown. In addition, the numerical value of each Example and each comparative example is as follows.
Example 1: a group · 8 pieces, b group · 0 pieces, c group · 0 pieces, Comparative Example 1: a group · 18 pieces, b group · 14 pieces, c group · 2 pieces, Comparative Example 2: a group 15 groups, b groups, 6 groups, c groups, 1 group, Comparative Example 3: a group, 11 groups, b group, 2 groups, c group, 0 groups.
From the above test results, it can be seen that Example 1 has better antifouling properties against marine organisms than Comparative Example 1, Comparative Example 2, and Comparative Example 3. Moreover, in Example 1, the number of b group and c group is 0, and especially the adhesion of a large barnacle is prevented. This is considered to be due to the barnacle adhering to the test piece not growing and dropping off early. Therefore, by depositing a Co-based alloy film by high-speed flame spraying, large barnacles are prevented from adhering to marine propellers, and the impact of marine organisms on ship speed and fuel efficiency is reduced. You can see that

  In order to observe the erosion state of the barnacle on the Co-based alloy film formed on the base material, the inventor further observed the cross section at the interface portion between the film and the barnacle, and the base material that was not formed as a comparison. A cross-sectional observation was performed at the interface between the barnacle and the barnacle. A test piece (with a coating) is obtained by immersing a base material (CAC703) on which a 0.5 mm Co-based alloy coating (Co-based alloy is the composition of the above embodiment) by high-speed flame spraying is immersed in the sea. Made. The test piece (no film) was prepared by immersing the base material in the sea. In order to observe the erosion state of the barnacle, the immersion period in the sea was a period until the barnacle adhering to the test piece (with a film) grew to a large size. Cross-sectional observation was performed using a scanning electron microscope. For the test piece (no film), component analysis was performed at the interface portion in order to more clearly determine the degree of barnacle erosion.

  In FIG. 5, the surface photograph of the test piece S (with a film | membrane) to which the large barnacle 30 adhered is shown. A line A in FIG. 5 is a cross-sectional observation portion in a portion where the barnacle 30 is not attached, and a B line in FIG. 5 is a cross-sectional observation portion in a portion where the barnacle 30 is attached. FIG. 6 is a cross-sectional image taken along line A in FIG. 5 and shows the surface layer portion of the test piece S. FIG. 7 is a cross-sectional image taken along line B of FIG. 5 and shows the interface K1 portion between the film 21 and the barnacle 30 in the portion where the barnacle 30 is attached to the test piece S. FIG. 8 shows a cross-sectional analysis image at the interface K2 portion between the base material 40 and the barnacle 30 in the part where the barnacle 30 is attached to the test piece (without film).

  As can be seen from the cross-sectional image in FIG. 7, the interface K <b> 1 between the film 21 and the barnacle 30 is linear, and not only the base material 20 (see the photograph in FIG. 6) that does not appear in the cross-sectional image, but the film 21. There is no damage, and no erosion of the barnacle 30 on the substrate 20 and the coating 21 is observed. On the other hand, as can be seen from the cross-sectional analysis image of FIG. 8, the interface K <b> 2 between the base material 40 and the barnacle 30 is broken, and the component 30 s constituting the barnacle 30 intrudes into the base material 40 and enters the barnacle 30 with it. The component 40s constituting the base material 40 is taken in.

  Moreover, when the barnacle 30 adhering to the test piece S (with a film) in FIG. 5 was removed with high-pressure water, the film was not broken. On the other hand, when the barnacle adhering to the test piece (no film) was removed with high-pressure water, damage marks 401 remained on the base material 40 of the test piece as shown in FIG.

  In the case of a test piece without a film, it is recognized that the barnacle is apparently not in a state of simply attaching to the base material but in a fixed state in close contact with the base material. From these facts, it is understood that the damage of the marine propeller due to the separation of marine organisms from the marine propeller can be reduced by forming the Co-based alloy film by the high-speed flame spraying method.

  In addition, embodiment disclosed above and each Example are illustrations and are not restrictive. In the above embodiment, an example in which the film is formed on the entire propeller body has been described. However, the film may be formed on a local site of the propeller body depending on the size of the ship and the shape of the wing. Further, the thickness of the film may be changed according to a part where cavitation is likely to occur and a part where marine organisms are likely to adhere. In this case, the cost for film formation can be reduced. The scope of the present invention is not limited to the above-described embodiments and examples, but is indicated by the scope of the claims, and includes meanings equivalent to the scope of the claims and all modifications within the scope.

  The present invention is applied to a marine propeller that generates propulsive force in a hull.

DESCRIPTION OF SYMBOLS 1 Marine propeller 2 Surface layer 3 Shaft 4 Wing | wing part 5 Outer surface 6 Protective coating 10 Ultrasonic vibration type cavitation erosion test apparatus 20 Base material 21 Thermal spray coating 30 Barnacle (marine life)

Claims (1)

A propeller body for generating a propulsion force for propelling the hull, the propeller body including a shaft connected to a marine vessel propulsion device and a wing extending radially from the outer periphery of the shaft;
A protective coating formed on the outer surface of both the shaft and the wing,
The protective coating is formed by high-speed flame spraying or low-pressure plasma spraying, Ni: 3 mass % or less, Cr: 25-35 mass %, W: 4-20 mass %, Fe: 3 mass % or less, C: 4 mass %, The balance: formed of a Co-based alloy having a composition consisting of Co and inevitable impurities , the thickness of the protective film is 0.1 to 1.0 mm, and the surface of the protective film A marine propeller having a Vickers hardness of 200 or more .