A diesel engine coating and method of making the same

Abstract

The application discloses a diesel engine coating and a preparation method thereof. The diesel engine coating comprises, from the cylinder cover and the piston surface of the diesel engine outward, a third adhesive layer, a second adhesive layer, a first adhesive layer and a ceramic top surface layer, and the adhesion of each layer is coated by adopting a plasma spraying mode; the ceramic top surface layer is a coating with a columnar structure in the inside and comprises yttrium stabilized zirconia ceramic powder; the first adhesive layer comprises yttrium stabilized zirconia ceramic powder and hollow metal particles; the second adhesive layer and the third adhesive layer both comprise hollow metal particles and adhesive layer metal powder; the adhesive layer metal powder is NiCrAl or CoCrAl alloy powder; and the number of the hollow metal particles contained in the first adhesive layer, the second adhesive layer and the third adhesive layer is reduced in equal proportion from the first adhesive layer to the third adhesive layer. The diesel engine coating structure disclosed by the application can not only save coating materials, but also increase the service life of the diesel engine through the combination of the columnar structure and the hollow metal particles.

Description

Technical Field

[0001] This invention belongs to the field of combustion optimization for marine high-power-density diesel engines, specifically relating to a diesel engine coating with better heat insulation performance and service life under large marine power plants and its preparation method. Background Technology

[0002] Thermal barrier coatings were initially used in the aerospace industry to provide heat insulation and reduce the surface temperature of engine combustion chamber components. In recent years, with the development of internal combustion engine technology, the operating temperature of marine power plant combustion chambers can reach 1000℃. If the combustion gas temperature is further increased by optimizing the combustion method, the alloy materials constituting the combustion chamber will reach their limit temperature. At this point, the service life of the materials is significantly reduced, and the safety of the power plant cannot be guaranteed. Thermal barrier coatings, as a technology that can reduce the surface temperature of the substrate layer, have naturally become a research focus for researchers. Currently, based on structure, they are mainly classified into double-layer coatings, multi-layer coatings, and gradient coatings.

[0003] The double-layer coating mainly consists of a ceramic heat insulation layer and a metal bonding layer. It has a simple structure and mature technology, but the coating and the substrate are prone to large internal stress due to the mismatch of thermal expansion coefficients. Its seismic performance is generally poor and it is difficult to apply to large diesel engines.

[0004] Multilayer coatings add a sealing layer to a double-layer coating, which improves its oxidation and corrosion resistance, but its seismic performance is still generally average.

[0005] Gradient coatings are based on a double-layer coating system, in which the coefficient of thermal expansion is gradually changed by mixing metal powder and ceramic powder in a variable proportion in the binder layer. They provide good shock resistance while maintaining thermal insulation, but their preparation technology is quite complex and is still in the research stage.

[0006] Furthermore, the surface structure of the coating varies due to different spraying technologies. The layered structure formed by traditional atmospheric plasma spraying is simple to prepare, but it is easily corroded at high temperatures and prone to premature failure due to internal stress. The columnar structure formed by EB-PVD (electron beam physical vapor deposition) and PS-PVD (plasma physical vapor deposition) technologies can accumulate internal stress during the working cycle, which greatly increases the coating life, but the gaps between the columns will reduce its thermal conductivity. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a coating design with better thermal insulation performance and service life for large marine propulsion systems. The coating used in this invention is a modified gradient structure based on a double-layer structure. The bonding layer enhances its thermal insulation performance by increasing the content of hollow metal particles in each layer, while the top layer employs a columnar ceramic thermal insulation coating. The top layer, due to its contact with high-pressure gas, requires good shock resistance. The thermal insulation performance loss due to the columnar structure is compensated for by the air within the metal particles of the bonding layer. Engines employing this invention have sufficiently high power output, dissipate a significant amount of heat through the combustion chamber walls, and can operate under high loads for extended periods.

[0008] A diesel engine coating, wherein the cylinder head and piston surfaces of the diesel engine serve as the base layer, and the coating comprises, from the base layer outwards, a third adhesive layer, a second adhesive layer, a first adhesive layer and a ceramic top layer, wherein the adhesive of each layer is applied by plasma spraying.

[0009] The ceramic top layer is a coating with a columnar structure, comprising yttrium-stabilized zirconia ceramic powder;

[0010] The first adhesive layer comprises yttrium-stabilized zirconia ceramic powder and hollow metal particles;

[0011] Both the second and third adhesive layers comprise hollow metal particles and adhesive layer metal powder; wherein the adhesive layer metal powder is NiCrAl or CoCrAl alloy powder; and the hollow metal particles are made of one of the aforementioned alloys and have a diameter of 0.05-0.08 mm.

[0012] The particle size of the metal powder and YSZ ceramic powder is 1-3 μm;

[0013] The number of hollow metal particles contained in the first adhesive layer, the second adhesive layer, and the third adhesive layer decreases proportionally in that order.

[0014] Furthermore, the ceramic top layer is formed into a columnar structure on the substrate layer using a plasma physical vapor deposition method.

[0015] Furthermore, the ceramic top layer also includes a binder layer of metal powder, wherein the YSZ ceramic powder is composed of ZrO2 and Y2O3, with the mass ratio of Y2O3 being 3%-8%.

[0016] Furthermore, the total thickness of the coating is 0.5 mm, wherein the thickness of the first adhesive layer, the second adhesive layer and the third adhesive layer are all 0.1 mm, and the thickness of the ceramic top layer is 0.2 mm.

[0017] The method for preparing the diesel engine coating includes:

[0018] Clean the substrate layer to be coated, removing oil stains and solid residues;

[0019] Multiple hollow metal particles are placed on the surface of the piston substrate layer, wherein the total volume of the metal particles accounts for 10-25% of the volume of the third adhesive layer; the hollow metal particles are fixed on the surface of the substrate layer, and then the adhesive layer metal powder is sprayed onto the hollow metal particles using atmospheric plasma until all metal particles are submerged, and then cooled to form the third adhesive layer.

[0020] Multiple hollow metal particles are placed on the surface of the third adhesive layer, wherein the total volume of the metal particles accounts for 25-50% of the volume of the second adhesive layer; the hollow metal particles are fixed on the surface of the third adhesive layer, and then the adhesive layer metal powder is sprayed onto the hollow metal particles using atmospheric plasma until all metal particles are submerged, and then cooled to form the second adhesive layer.

[0021] Hollow metal particles are placed on the surface of the second adhesive layer, wherein the total volume of the metal particles accounts for 30-75% of the volume of the second adhesive layer; the hollow metal particles are fixed on the surface of the second adhesive layer, and then YSZ ceramic powder is sprayed onto the hollow metal particles using atmospheric plasma until all metal particles are submerged, and then cooled to form the first adhesive layer.

[0022] YSZ ceramic powder was uniformly sprayed onto the surface of the first adhesive layer using plasma physical vapor deposition and then cooled to form a ceramic top layer with a columnar structure.

[0023] Furthermore, each surface can be prepared into another layer without polishing after preparation, thereby increasing the friction of the metal particles.

[0024] A marine power unit includes a diesel engine, wherein the cylinder head and piston surfaces of the diesel engine are coated with the coating.

[0025] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0026] The diesel engine coating structure proposed in this invention, while meeting the heat insulation requirements of large-scale diesel engines, combines a columnar structure with hollow metal particles. This not only saves on coating material but also withstands the harsh high-temperature and high-pressure operating environment of large-scale diesel engines, increasing their service life. It is suitable for retrofitting existing diesel engines in large ships, allowing the coating to be added to existing engines to further extend their lifespan. Attached Figure Description

[0027] Figure 1 This is a flowchart of the preparation of the engine coating described in Example 1 of the present invention;

[0028] Figure 2 This is a cross-sectional view of the coating described in Example 1.

[0029] in,

[0030] 1: Ceramic top layer; 2: First adhesive layer; 3: Second adhesive layer

[0031] 4: Third adhesive layer; 5: Substrate layer; 6: Hollow metal particles Detailed Implementation

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The specific embodiments described are only for explanation and illustration of the present invention and are not intended to limit the present invention.

[0033] Example 1

[0034] A diesel engine coating is disclosed. This coating is primarily used in applications requiring high thermal stress and insulation. Therefore, the coating is applied to the cylinder head and piston surface; the cylinder wall and piston rings are temporarily disregarded due to friction. Taking the piston as an example, the piston surface serves as the base layer 5. The coating, extending outwards from the piston surface (base layer 5), comprises: a third adhesive layer 4, a second adhesive layer 3, a first adhesive layer 2, and a ceramic top layer 1.

[0035] The ceramic top layer 1 is a ceramic heat-insulating coating with an internal columnar structure. It is made of yttrium-stabilized zirconia (YSZ) ceramic, and the ceramic powder used is widely available yttrium zirconia (YSZ). YSZ has excellent heat insulation properties and good mechanical properties. Since the ceramic top layer 1 is mainly in contact with the high-temperature, high-pressure gas in the combustion chamber, the columnar structure formed by plasma phase deposition has a larger strain space compared to a layered structure. The protruding ceramic crystal pillars at high temperatures can expand through the gaps, reducing internal stress in the coating and increasing seismic resistance.

[0036] The materials of the second adhesive layer 3 and the third adhesive layer 4 both include a mixture of hollow metal particles and metal powder, while the material of the first adhesive layer 2 is a mixture of hollow metal particles and YSZ ceramic powder. From the first adhesive layer to the third adhesive layer, the number of hollow metal particles contained in each layer decreases proportionally.

[0037] The particle size of the metal powder and YSZ ceramic powder is 1-3 μm.

[0038] The ceramic top layer 1 is sprayed onto the surface of the first adhesive layer 2 by plasma physical vapor deposition, and the bonding between the first adhesive layer 2, the second adhesive layer 3 and the third adhesive layer 4 is achieved by plasma spraying.

[0039] Figure 1 This paper illustrates a coating preparation method for a medium-speed four-stroke diesel engine, taking the piston surface as an example. The specific method is as follows:

[0040] Clean the surface of the piston substrate layer 5 to be coated with oil stains and solid residues; there is no need to polish the surface of the substrate layer 5.

[0041] Multiple hollow metal particles of equal diameter are placed on the surface of the piston substrate layer 5, wherein the total volume of the metal particles accounts for approximately 20% of the volume of the third adhesive layer 4. Considering that the metal particles may scatter during spraying, the hollow metal particles are fixed to the surface of the substrate layer 5 by welding. Then, atmospheric plasma spraying is used to fill the remaining gaps with adhesive layer metal powder until all metal particles are submerged. After cooling, a third adhesive layer 4 with a thickness of 0.1 mm is formed. The adhesive layer metal powder is NiCrAl nickel-based alloy powder. The diameter of the hollow metal particles is 0.05-0.08 mm.

[0042] Without grinding the outer surface of the third adhesive layer, hollow metal particles of equal diameter are placed on the surface of the third adhesive layer 4, wherein the total volume of the metal particles accounts for about 40% of the volume of the third adhesive layer 4; the hollow metal particles are fixed to the surface of the third adhesive layer 4 by welding; then, atmospheric plasma spraying of adhesive layer metal powder is used to fill the remaining gaps until all metal particles in the layer are submerged; after cooling, a second adhesive layer 3 with a thickness of 0.1 mm is formed; and the number of hollow metal particles in this layer is greater than the number of hollow metal particles in the third adhesive layer 4.

[0043] Without grinding the outer surface of the second adhesive layer, hollow metal particles of equal diameter are placed on the surface of the second adhesive layer 3, wherein the total volume of the metal particles accounts for about 60% of the volume of the second adhesive layer 3. The hollow metal particles are fixed to the surface of the second adhesive layer 3 by welding. Then, YSZ ceramic powder is sprayed using atmospheric plasma to fill the remaining gaps until all metal particles in the layer are submerged. After cooling, a first adhesive layer 2 with a thickness of 0.1 mm is formed; and the number of hollow metal particles in this layer is greater than the number of hollow metal particles in the second adhesive layer 3.

[0044] Afterwards, without grinding the outer surface of the first adhesive layer, YSZ ceramic powder is uniformly sprayed onto the surface of the first adhesive layer 2 using plasma physical vapor deposition and cooled, thereby forming a ceramic top layer 1 with a thickness of 0.2 mm and a columnar structure on the surface of the first adhesive layer.

[0045] The coating application is now complete.

[0046] Example 2

[0047] This embodiment is similar to Embodiment 1, and the same content will not be repeated. The only difference is in the preparation of the first, second, and third adhesive layers. The following only describes the differences.

[0048] The preparation method of the third adhesive layer is as follows: a portion of the adhesive layer metal powder is sprayed onto the surface of the substrate layer 5 using atmospheric plasma, with a thickness of 20% of the thickness of the third adhesive layer. Multiple hollow metal particles of equal diameter are welded onto the sprayed metal powder surface, wherein the total volume of the metal particles accounts for about 15% of the volume of the third adhesive layer 4. Subsequently, the remaining gaps are filled by spraying the adhesive layer metal powder using atmospheric plasma until all metal particles are submerged. The mixture is then cooled to room temperature to form the third adhesive layer 4. The adhesive layer metal powder is CoCrAl alloy powder.

[0049] The preparation method of the second adhesive layer is as follows: without grinding the outer surface of the third adhesive layer, a portion of the adhesive layer metal powder is sprayed onto the surface of the third adhesive layer using atmospheric plasma, with a thickness of 20% of the thickness of the second adhesive layer. Multiple hollow metal particles of equal diameter are welded onto the sprayed metal powder surface, wherein the total volume of the metal particles accounts for about 30% of the volume of the second adhesive layer. Subsequently, the adhesive layer metal powder is sprayed with atmospheric plasma to fill the remaining gaps until all metal particles are submerged. After cooling to room temperature, the second adhesive layer 3 is formed. The adhesive layer metal powder is CoCrAl alloy powder.

[0050] The preparation method of the first adhesive layer is as follows: Without grinding the outer surface of the second adhesive layer, a mixture of adhesive layer metal powder and YSZ ceramic powder is sprayed onto the surface of the second adhesive layer using atmospheric plasma spraying, with a thickness of 20% of the thickness of the second adhesive layer. Multiple hollow metal particles of equal diameter are welded to the sprayed mixture powder surface, wherein the total volume of the metal particles accounts for approximately 45% of the volume of the first adhesive layer. The hollow metal particles are fixed to the freshly sprayed mixture powder surface using a welding method. Subsequently, atmospheric plasma spraying of the adhesive layer metal powder and YSZ ceramic powder fills the remaining gaps, spraying until all metal particles are submerged, and cooling is performed to form the first adhesive layer 2. In this embodiment, the YSZ ceramic powder and metal particles, after being mixed, have good thermal expansion matching with the hollow metal particles, wherein the mass ratio of Y2O3 in the YSZ ceramic powder is 3%-8%.

[0051] The total thickness of the coating is 0.5 mm, of which the thickness of the first adhesive layer 2, the second adhesive layer 3 and the third adhesive layer 4 are all 0.1 mm, and the thickness of the ceramic top layer 1 is 0.2 mm.

[0052] The thermal insulation and seismic resistance principles of the coating obtained according to the above preparation method are as follows: The ceramic top layer 1 is mainly in contact with high-pressure gas, and at the same time, it has certain thermal insulation properties, bears a large thermal stress, and the columnar structure of the ceramic top layer 1 itself has a certain seismic resistance. Compared with ordinary layered structures, the number of hollow metal particles inside the first to third adhesive layers gradually decreases. Each adhesive layer, as a supplement to the thermal insulation performance of the ceramic top layer 1, further enhances the thermal insulation performance of the coating.

[0053] Although preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these are within the scope of protection of the present invention.

Claims

1. A diesel engine coating, characterized in that, The cylinder head and piston surface of the diesel engine serve as the base layer (5). The coating layer from the base layer (5) outwards includes: a third adhesive layer (4), a second adhesive layer (3), a first adhesive layer (2), and a ceramic top layer (1). The bonding of each layer is achieved by plasma spraying. The ceramic top layer (1) is a coating with a columnar structure, comprising yttrium-stabilized zirconia ceramic powder; The first adhesive layer (2) comprises yttrium-stabilized zirconia ceramic powder and hollow metal particles; The second adhesive layer (3) and the third adhesive layer (4) both include hollow metal particles and adhesive layer metal powder; wherein, the adhesive layer metal powder is NiCrAl or CoCrAl alloy powder; the hollow metal particles are made of one of the above alloys and have a diameter of 0.05-0.08 mm; The particle size of the metal powder and YSZ ceramic powder is 1-3 μm; The number of hollow metal particles contained in the first adhesive layer, the second adhesive layer, and the third adhesive layer decreases proportionally in sequence. The total volume of hollow metal particles in the first adhesive layer accounts for 30%-75% of the volume of the first adhesive layer, the total volume of hollow metal particles in the second adhesive layer accounts for 25%-50% of the volume of the second adhesive layer, and the total volume of hollow metal particles in the third adhesive layer accounts for 10%-25% of the volume of the third adhesive layer; The ceramic top layer (1) is formed into a columnar structure on the substrate layer (5) using a plasma physical vapor deposition method; The ceramic top layer (1) also includes a bonding layer of metal powder, wherein the mass fraction of Y2O3 in the YSZ ceramic powder is 3%-8%.

2. The diesel engine coating according to claim 1, characterized in that, The total thickness of the coating is 0.5 mm, of which the thickness of the first adhesive layer (2), the second adhesive layer (3) and the third adhesive layer (4) is 0.1 mm, and the thickness of the ceramic top layer (1) is 0.2 mm.

3. The method for preparing a diesel engine coating according to claim 1, characterized in that, include: Clean the substrate layer to be coated (5) of oil stains and solid residues; Multiple hollow metal particles are placed on the surface of the piston substrate layer (5), wherein the total volume of the metal particles accounts for 10-25% of the volume of the third adhesive layer (4); the hollow metal particles are fixed on the surface of the substrate layer (5), and then the adhesive layer metal powder is sprayed onto the hollow metal particles using atmospheric plasma until all metal particles are submerged, and then cooled to form the third adhesive layer (4). Multiple hollow metal particles are placed on the surface of the third adhesive layer (4), wherein the total volume of the metal particles accounts for 25-50% of the volume of the second adhesive layer (3); the hollow metal particles are fixed on the surface of the third adhesive layer (4), and then the adhesive layer metal powder is sprayed onto the hollow metal particles using atmospheric plasma until all metal particles are submerged, and cooled to form the second adhesive layer (3). Hollow metal particles are placed on the surface of the second adhesive layer (3), wherein the total volume of the metal particles accounts for 30-75% of the volume of the second adhesive layer (3); the hollow metal particles are fixed on the surface of the second adhesive layer (3), and then YSZ ceramic powder is sprayed onto the hollow metal particles using atmospheric plasma until all metal particles are submerged, and cooled to form the first adhesive layer (2). YSZ ceramic powder was uniformly sprayed onto the surface of the first adhesive layer (2) using plasma physical vapor deposition and cooled to form a ceramic top layer (1) with a columnar structure.

4. A marine propulsion system, comprising a diesel engine, characterized in that, The cylinder head and piston surfaces of the diesel engine are coated with the coating as described in any one of claims 1-2.

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