Composite material for diesel engine cylinder head components and method of making same

Abstract

The application discloses a composite material for a cylinder head part of a diesel engine and a preparation method thereof, the composite material comprising an upper alloy layer, a lower alloy layer, and a composite layer between the upper alloy layer and the lower alloy layer, the macro hardness of the composite material being 51.2-58.6 HRC, and the friction coefficient under a simulated low-sulfur complex acidic working condition being 0.052-0.180; the application can improve the strength of the composite material and play a good supporting role on the surface self-lubricating film, and the high-thermal-conductivity AlN in the composite material can effectively improve the thermal conductivity coefficient, and finally prolong the service life of the overall material.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, and particularly relates to composite materials for diesel engine cylinder head components and their preparation methods. Background Technology

[0002] High-power-density diesel engines, serving as the "heart" of armored vehicles, require high performance, small size, and light weight to meet the demands of new service environments. Among these components, the cylinder head of a diesel engine is subjected to the harshest service conditions. During operation, it not only endures high temperatures and pressures but also corrosive atmospheres, resulting in severe wear and tear, and is highly susceptible to low-sulfur frictional wear damage. Similarly, the cylinder heads of civilian heavy trucks also face similarly demanding service conditions.

[0003] For cylinder head materials, this is not simply a process of impact between the valve pushrod and the cylinder head material (valve seat bore). It primarily involves corrosion due to poor lubrication and acidic substances. Fuels contain a certain proportion of sulfur, which, upon combustion, produces oxides that combine with water in the combustion products to form sulfuric acid vapor. This vapor condenses and contacts the cylinder wall, causing corrosion. Other factors include mechanical wear due to high pressure, and frictional wear under complex low-sulfur conditions when the air entering the cylinder contains dust or the lubricating oil contains impurities. With the rapid development of carbon neutrality and technology, the pressure on traditional energy industries is increasing. Extending equipment service life and expanding the application of remanufacturing technology have become important ways to reduce emissions in energy equipment. Methanol-diesel dual-fuel combustion is a technology that is beneficial for energy conservation and emission reduction, reduces diesel consumption, and is easy to promote. Therefore, developing a cylinder head material for methanol-diesel dual-fuel engines is urgently needed.

[0004] The traditional method for preparing cylinder head materials in service is mainly sand casting. This method has low production efficiency, low yield, and low surface quality. Moreover, the wear of the valve seat hole area during service can easily lead to cylinder head failure. If the wear performance of the corresponding position of the finished cylinder head is to be improved, the improvement methods include surface treatment, spraying, laser cladding and other technologies. However, because the shape of the valve seat hole area corresponding to the cylinder head is relatively complex, it is difficult to control the uniformity of the surface layer after surface treatment, which leads to poor secondary treatment effect. Summary of the Invention

[0005] The purpose of this invention is to provide an acid-resistant and wear-resistant composite material for manufacturing cylinder head parts and a method for preparing the same. The composite material can be used to prepare an integrally formed acid-resistant and wear-resistant cylinder head part, and the finished product does not require secondary surface treatment.

[0006] The present invention adopts the following technical solution: a composite material for diesel engine cylinder head parts, comprising an upper alloy layer, a lower alloy layer, and a composite layer located between the upper alloy layer and the lower alloy layer, wherein the macroscopic hardness of the composite material is 51.2-58.6 HRC, and the coefficient of friction under simulated low sulfur complex acidic conditions is 0.052-0.180.

[0007] A method for preparing composite materials for diesel engine cylinder head components includes:

[0008] Step 1:

[0009] Fe, Mn, Al, Ni, C, and Ti powders were weighed, ball-milled, and mixed to obtain alloy powder.

[0010] Weigh out AlN powder and raw material powder, ball mill them, and mix them thoroughly to obtain composite powder.

[0011] Step 2:

[0012] A layer of alloy powder is filled into a graphite mold to form the first layer of alloy powder, then composite powder is filled in, and finally another layer of alloy powder is filled in to form the second layer of alloy powder. The block composite material is obtained by vacuum hot pressing sintering.

[0013] Furthermore, in step 1, the mass fractions Fe:Mn:Al:Ni:C:Ti are 56.8:25:9:8:1:0.2.

[0014] Furthermore, in step 2, the raw material powder is Fe powder, Al powder, or alloy powder; the mass fraction ratio of AlN powder to raw material powder in step 2 is 1:9.

[0015] Furthermore, in step 2, the composite powder accounts for 1-5% of the total amount of the first layer alloy powder, the composite powder, and the second layer alloy powder, and the mass fraction ratio of the first layer alloy powder to the second layer alloy powder is 1:1.

[0016] Furthermore, in step 2, the first layer of alloy powder is first filled and compacted by cold pressing, then composite powder is sieved in through a double screen device, and finally the second layer of alloy powder is filled and compacted by cold pressing.

[0017] Furthermore, the dual-screen device includes an upper screen mechanism located on the upper side and a lower screen mechanism located on the lower side. The upper screen mechanism and the lower screen mechanism are coaxially arranged. The screen hole shapes of the upper screen mechanism and the lower screen mechanism are different, and are used to achieve good dispersion of composite powder by utilizing the different screening efficiencies of the different screen hole shapes.

[0018] The upper screening mechanism includes components that are all coaxially arranged:

[0019] The upper fixed ring is set horizontally.

[0020] The upper screen is made of rubber cloth with circular holes, located inside the upper fixing ring. The outer edge of the upper screen is fixedly connected to the inner edge of the upper fixing ring.

[0021] The upper ejector ring is horizontally positioned below the upper screen. When the upper fixed ring is pressed down, the upper ejector ring pushes the upper screen upward, thereby increasing the aperture of the upper screen so that the agglomerated composite powder on the upper screen can be dispersed and fall off.

[0022] Furthermore, the lower screening mechanism includes components all coaxially arranged:

[0023] The lower fixed ring is set horizontally.

[0024] The lower screen is made of rubber cloth with square holes, located inside the lower fixed ring. The outer edge of the lower screen is fixedly connected to the inner edge of the lower fixed ring.

[0025] The lower ejector ring is horizontally positioned below the lower screen. When the lower fixing ring is pushed downwards, the lower ejector ring pushes the lower screen upwards, thereby increasing the aperture of the lower screen so that the composite powder smoothed by the scraper mechanism on the lower screen can be sieved into the graphite mold.

[0026] Furthermore, a circular groove is formed on the upper side of the upper ejector ring from top to bottom. The axis of the groove coincides with the axis of the upper ejector ring. The groove is used for the scraper mechanism to extend into, so that the scraper mechanism can flatten the composite powder accumulated on the lower screen, and thus the composite powder can be dispersed again when passing through the lower screen.

[0027] Furthermore, the scraper mechanism includes:

[0028] The first upright post is set vertically, with its lower end extending into the groove.

[0029] The lower retaining ring, fitted onto the lower half of the first upright, abuts against the edge of the groove of the upper ejector ring, thereby limiting the depth to which the first upright extends into the groove.

[0030] The upper retaining ring is fitted onto the upper half of the first upright.

[0031] The lever is horizontally positioned, with one end fitted onto the upper half of the first upright and resting on the upper retaining ring, thus allowing the upper retaining ring to support the lever.

[0032] The scraper is vertically positioned, with its upper end fixedly connected to the lever, and its lower end extending downwards and into the inner cavity of the upper ejector ring.

[0033] The second upright is set vertically, and its lower end is fixedly connected to the other end of the lever. It is used to cooperate with the first upright so that the axis of the ejector ring above the scraper rotates, thereby flattening the composite powder accumulated on the lower screen.

[0034] The beneficial effects of this invention are:

[0035] 1. This invention improves the mechanical and thermal properties of the overall material by adding AlN, which has a high thermal conductivity of up to 320 W / (m·k) and a hardness of up to 36 GPa. In addition, it improves the strength of the composite material and provides good support for the self-lubricating film on the surface. The high thermal conductivity of AlN in the composite material can effectively improve its thermal conductivity, and ultimately extend the service life of the overall material.

[0036] 2. This invention does not require secondary surface treatment. In the current diesel engine, the valve seat hole area of ​​the cast iron cylinder head usually requires the preparation of a surface wear-resistant layer such as laser cladding, physical deposition or chemical deposition on the surface of the casting. However, the parts prepared by the composite material of this invention are formed in one step and have good wear resistance. No secondary processing steps are required, thereby saving manpower, time and resources and greatly reducing the cost of the finished product.

[0037] 3. This invention utilizes a double-screen device to sieve the composite powder. During the sieving process, the composite powder is first evenly spread on the upper screen. Then, when the upper fixing ring is pressed down, the upper ejector ring lifts the upper screen upward, thereby increasing the aperture of the upper screen. This allows any agglomerated composite powder on the upper screen to be dispersed and fall onto the upper side of the lower screen. A scraper mechanism then smooths out the accumulated composite powder on the lower screen. Finally, when the lower fixing ring is pushed down, the lower ejector ring lifts the lower screen upward, further increasing the aperture of the lower screen. This allows the powder smoothed by the scraper mechanism to be further dispersed. The composite powder is sieved into a graphite mold. This invention utilizes a double-sieve device to sieve the composite powder. When no external force is applied, the holes of the upper and lower sieves are closed. When subjected to an outward horizontal pulling force, the rubber cloth is tightened, and the hole diameter gradually increases. After the external force is removed, the holes of the rubber cloth relax and close. The composite powder after two sieves is more dispersed and uniform, avoiding agglomeration due to long storage time and high specific surface energy of powder particles. This results in good dispersibility of the composite powder without agglomeration, which in turn makes the subsequent sintered sample structure more uniform and the composite layer height more uniform, so that the composite layer has a good strengthening effect.

[0038] 4. Under simulated complex acidic conditions, the wear surface of this invention can continuously generate a FeS self-lubricating film. FeS has a two-dimensional layered structure. This material can play a role in reducing friction during the friction and wear process. This indicates that the material can reduce the friction coefficient by forming a self-lubricating film on the wear surface with the help of a sulfur-containing atmosphere, and significantly improve the wear performance. In particular, the friction coefficient is reduced by 1.6%-71.6% compared with Comparative Example 1, which shows the application potential of the cylinder head material of the engine under methanol and diesel dual-fuel combined conditions.

[0039] 5. The thickness of the composite layer can be increased or decreased according to the thickness of the stress surface. Different parts of the diesel engine cylinder head have different requirements for material hardness and strength. The thickness of the composite layer of the present invention is controllable and can be adjusted according to the required strength.

[0040] 6. The upper alloy layer, composite layer and lower alloy layer of the present invention have good physical and chemical compatibility. The hot pressing sintering process enables the three alloy layers to be metallurgically bonded, avoiding the use of binders, reducing the introduction of impurities, and thus improving the purity of the composite material. Therefore, the present invention simplifies the preparation process and reduces costs.

[0041] 7. The composite material prepared by the present invention exhibits good metallurgical bonding between the upper alloy layer, the composite layer, and the lower alloy layer. Compared with the wear-resistant surface prepared by traditional methods such as laser cladding and chemical deposition, the material bonding in the present invention is tighter, thereby avoiding cracking or even peeling caused by corrosion, oxidation, wear, etc., and extending the service life of the finished product.

[0042] 8. The microhardness of the present invention gradually increases from the upper alloy layer and the lower alloy layer to the composite layer. In actual use, the high-strength composite layer located in the middle can effectively support the upper alloy layer and the lower alloy layer. Even when the upper alloy layer and the lower alloy layer soften at high temperature, the middle composite layer can still play a good supporting role, thus extending the service life of the finished product.

[0043] 9. The scraper mechanism of the present invention can smooth the composite powder on the lower screen, thereby making the composite powder fall more evenly and avoiding the phenomenon of central aggregation, which would affect the uniformity of the sintered sample structure. Furthermore, by setting the upper retaining ring, the lever can be moved up and down, thereby changing the height of the scraper extending into the inner cavity of the upper ejector ring and avoiding the scraper compacting the composite powder. Instead, it smooths the composite powder while ensuring that the composite powder is dispersed, thus preventing the composite powder from agglomerating in the central area due to its high specific surface energy. Attached Figure Description

[0044] Figure 1 (a) is a scanning electron microscope image of the bulk composite material of Comparative Example 1;

[0045] Figure 1 (b) is a scanning electron microscope image of the bulk composite material in Example 3;

[0046] Figure 1 (c) XRD patterns of the bulk composite materials of Comparative Example 1 and Example 3;

[0047] Figure 2 (a) is a wear surface morphology diagram of the composite material prepared in Comparative Example 1 under complex acidic conditions.

[0048] Figure 2(b) is a wear surface morphology diagram of the composite material prepared in Example 3 under complex acidic conditions;

[0049] Figure 3 This is a schematic diagram showing that the microhardness of the composite material gradually increases from the upper alloy layer and the lower alloy layer to the composite layer.

[0050] Figure 4 (a) is a diagram showing the elemental distribution of the wear surface of the composite material prepared in Example 3;

[0051] Figure 4 (b) is the Raman spectrum of the composite material prepared in Example 3.

[0052] Figure 5 This is an isometric view of the double-screen device;

[0053] Figure 6 This is a schematic diagram of the double-screen device;

[0054] Figure 7 This is a schematic diagram of the scraper mechanism.

[0055] The components are: 1. Upper fixed ring; 2. Upper screen; 3. Upper ejector ring; 4. Lower fixed ring; 5. Lower screen; 6. Lower ejector ring; 7. Groove; 8. Scraper mechanism; 9. First upright; 10. Lower retaining ring; 11. Upper retaining ring; 12. Lever; 13. Scraper; 14. Second upright. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0057] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0058] This invention discloses a composite material for diesel engine cylinder head components, comprising an upper alloy layer, a lower alloy layer, and a composite layer located between the upper alloy layer and the lower alloy layer. The composite material has a macroscopic hardness of 51.2-58.6 HRC and a friction coefficient of 0.052-0.180 under simulated low-sulfur complex acidic conditions.

[0059] This invention also discloses a method for preparing composite materials for diesel engine cylinder head components, comprising:

[0060] Step 1:

[0061] Fe, Mn, Al, Ni, C, and Ti powders were weighed, ball-milled, and mixed to obtain alloy powder.

[0062] Weigh out AlN powder and raw material powder, ball mill them, and mix them thoroughly to obtain composite powder.

[0063] Step 2:

[0064] A layer of alloy powder is filled into a graphite mold to form the first layer of alloy powder, then composite powder is filled in, and finally another layer of alloy powder is filled in to form the second layer of alloy powder. The block composite material is obtained by vacuum hot pressing sintering.

[0065] In step 1, the mass fraction Fe:Mn:Al:Ni:C:Ti is 56.8:25:9:8:1:0.2.

[0066] In step 2, the raw material powder is Fe powder, Al powder, or alloy powder; the mass fraction ratio of AlN powder to raw material powder in step 2 is 1:9. In step 2, the composite powder accounts for 1-5% of the total amount of the first layer of alloy powder, the composite powder, and the second layer of alloy powder, and the mass fraction ratio of the first layer of alloy powder to the second layer of alloy powder is 1:1. In step 2, the first layer of alloy powder is first filled and compacted by cold pressing, then the composite powder is sieved through a double-screen device, and finally the second layer of alloy powder is filled and compacted by cold pressing.

[0067] The ball milling conditions for the alloy powder in step 1 are as follows: alloy powder to grinding balls mass ratio = 1:10, rotation speed 250 r / min, time 20 h. During the ball milling process, methanol (5% of the total mass of raw materials) is added together with the powder and placed into a vacuum-sealed ball mill jar filled with argon gas. The ball milling conditions for the composite powder in step 1 are as follows: alloy powder to grinding balls mass ratio = 1:3, rotation speed 150 r / min, time 2 h. The ball mill jar and grinding balls are made of zirconium oxide, and the diameters of the grinding balls are 3 mm, 5 mm, and 8 mm, respectively. The grinding ball ratio is as follows: The mixing method is continuous mixing, that is, dry mixing preparation under an argon atmosphere.

[0068] The hot-pressing sintering conditions in step 2 are as follows: vacuum degree of 3-4 Pa, sintering temperature of 1070℃, sintering pressure of 25 MPa, and automatic heating during the hot-pressing sintering process, which covers the temperature range from room temperature to 1070℃. Specifically, the heating rate is 5-10℃ / min in the room temperature to 300℃ range, 10-15℃ / min in the 300-900℃ range, 45-50℃ / min in the 900-1000℃ range, and 3-8℃ / min in the 1000-1070℃ range. The sintering temperature is held at 1070℃ for 120 min, and then cooled to room temperature in the furnace.

[0069] like Figure 5-6As shown, the double-screen device includes an upper screen mechanism located on the upper side and a lower screen mechanism located on the lower side. The upper screen mechanism and the lower screen mechanism are coaxially arranged. The screen hole shapes of the upper screen mechanism and the lower screen mechanism are different, and are used to achieve good dispersion of composite powder by utilizing the different screening efficiencies of the different screen hole shapes.

[0070] The upper sieve mechanism includes an upper fixed ring 1, an upper screen 2, and an upper ejector ring 3, all coaxially arranged. The upper fixed ring 1 is horizontally arranged. The upper screen 2 is made of rubber cloth and has circular holes. The upper screen 2 is located in the inner cavity of the upper fixed ring 1, and the outer edge of the upper screen 2 is fixedly connected to the inner edge of the upper fixed ring 1.

[0071] The upper ejector ring 3 is set horizontally and is located below the upper screen 2. When the upper fixed ring 1 is pressed down, the upper ejector ring 3 pushes the upper screen 2 upward, thereby increasing the aperture of the upper screen 2 so that the agglomerated composite powder on the upper screen 2 can be dispersed and fall off.

[0072] The lower sieve mechanism includes a lower fixed ring 4, a lower screen 5, and a lower ejector ring 6, all coaxially arranged. The lower fixed ring 4 is horizontally arranged. The lower screen 5 is made of rubber cloth and has square holes. The lower screen 5 is located in the inner cavity of the lower fixed ring 4, and the outer edge of the lower screen 5 is fixedly connected to the inner edge of the lower fixed ring 4.

[0073] The lower ejector ring 6 is set horizontally and is located on the lower side of the lower screen 5. When the lower fixed ring 4 is pushed down, the lower ejector ring 6 pushes the lower screen 5 up, thereby increasing the aperture of the lower screen 5 so that the composite powder on the lower screen 5, which has been smoothed by the scraper mechanism 8, can be screened into the graphite mold.

[0074] A circular groove 7 is provided on the upper side of the upper ejector ring 3 from top to bottom. The axis of the groove 7 coincides with the axis of the upper ejector ring 3. The groove 7 is used for the scraper mechanism 8 to extend into, so that the scraper mechanism 8 flattens the composite powder accumulated on the lower screen 5, so that the composite powder is dispersed again when passing through the lower screen 5 and falls evenly into the graphite mold, so that the overall composite powder layer has a consistent height.

[0075] The scraper mechanism 8 includes: a first upright rod 9, a lower retaining ring 10, an upper retaining ring 11, a lever 12, a scraper 13, and a second upright rod 14.

[0076] The first upright 9 is set vertically, with its lower end extending into the groove 7. The lower retaining ring 10 is fitted onto the lower half of the first upright 9. The lower retaining ring 10 is used to abut against the edge of the groove 7 of the upper protruding ring 3, thereby limiting the depth of the first upright 9 extending into the groove 7.

[0077] The upper retaining ring 11 is fitted onto the upper half of the first upright 9. The lever 12 is set horizontally, with one end of the lever 12 fitted onto the upper half of the first upright 9 and resting on the upper side of the upper retaining ring 11, so that the upper retaining ring 11 supports the lever 12.

[0078] The scraper 13 is vertically arranged, and its upper end is fixedly connected to the lever 12. The lower end of the scraper 13 extends downward and into the inner cavity of the upper ejector ring 3. The second upright rod 14 is vertically arranged, and its lower end is fixedly connected to the other end of the lever 12. The second upright rod 14 is used to cooperate with the first upright rod 9 so that the axis of the upper ejector ring 3 of the scraper 13 rotates, thereby flattening the composite powder accumulated on the lower screen 5.

[0079] Example 1

[0080] Step 1:

[0081] Weigh out 24.75 g of Fe, Mn, Al, Ni, C, and Ti powders (total 24.75 g) and 1.24 g of methanol (5% of the total powder mass) according to the mass ratio of Fe:Mn:Al:Ni:C:Ti = 56.8:25:9:8:1:0.2, and place them into a zirconia ball mill jar. Add materials with diameters of 3 mm, 5 mm, and... 248g of zirconia grinding balls were used. Before ball milling, the grinding jar was sealed with an O-ring, evacuated, and filled with argon. The mixture was ball milled at a speed of 250r / min and a grinding time of 20h to obtain a uniformly mixed alloy powder.

[0082] The selected raw material powder was Fe powder. It was added to a zirconia ball mill jar at a mass ratio of Fe + AlN powder (9:1) (total 0.5g) and 5% methanol (0.025g) of the total mass of the composite powder. Powders with diameters of 3mm, 5mm, and [other components] were added. 1.5g of zirconia grinding balls were used. Before ball milling, the ball mill jar was sealed with an O-ring and then evacuated and filled with argon gas. The mixture was ball milled at a speed of 150r / min and a milling time of 2h to obtain a uniformly mixed composite powder.

[0083] Step 2:

[0084] Two portions of alloy powder (24.75g each) and composite powder (0.5g each) were weighed and loaded into a high-strength graphite mold in the order of alloy powder-composite powder-alloy powder. Sintering was then performed in a hot-pressing sintering furnace (ZT-40-20Y) manufactured by Shanghai Chenhua Electric Furnace Co., Ltd. The main sintering process parameters were: vacuum degree 3-4Pa, sintering pressure 25MPa, automatic heating during hot-pressing sintering, heating current 0.25KA; automatic heating: from room temperature to 1070℃ (i.e., from room temperature to 300℃), heating rate 5-10℃ / min; 300-900℃, heating rate 10-15℃ / min; 900-1000℃, heating rate 45-50℃ / min; 1000-1070℃, heating rate 3-8℃ / min; holding at 1070℃ for 120min, then cooling to room temperature with the furnace.

[0085] The sintered body of Example 1 was mechanically cut into wear samples of 15×15×8mm. The samples were immersed in a solution of 98% concentrated sulfuric acid: methanol: lubricating oil (HFV-vacuum pump oil) = 1:1:8 for 24 hours. After immersion, the samples were removed and excess solution on the surface was removed with oil-absorbing paper. The surface of the samples was kept in a complex acidic state. The treated samples were subjected to friction and wear tests using an MFT-R4000 high-speed reciprocating friction and wear tester. The friction frequency was 3Hz, the wear material was GCr15 (hardness 240HV), the wear load was 30N, and the friction stroke was 2.5mm.

[0086] Example 2

[0087] The specific operating steps in this embodiment are the same as those in Embodiment 1, except that the selected raw material powder is Al powder.

[0088] Example 3

[0089] The specific operation steps in this embodiment are the same as those in Embodiment 1, except that the selected raw material powder is alloy powder, that is, the alloy powder prepared in step 1.

[0090] Example 4

[0091] Step 1:

[0092] Weigh out 23.75 g of Fe, Mn, Al, Ni, C, and Ti powders (total 23.75 g) and 1.19 g of methanol (5% of the total powder mass) according to the mass ratio of Fe:Mn:Al:Ni:C:Ti = 56.8:25:9:8:1:0.2, and place them into a zirconia ball mill jar. Add materials with diameters of 3 mm, 5 mm, and... 238g of zirconia grinding balls were used. Before ball milling, the grinding jar was sealed with an O-ring, evacuated, and filled with argon. The mixture was ball milled at a speed of 250r / min and a grinding time of 20h to obtain a uniformly mixed alloy powder.

[0093] The selected raw material powder was Fe powder. The powder was added to a zirconia ball mill jar at a mass ratio of Fe + AlN powder (9:1) (total 2.5g) and 5% methanol (0.125g) of the total mass of the composite powder. Powders with diameters of 3mm, 5mm, and [other components] were added. 7.5g of zirconia grinding balls were used. Before ball milling, the ball mill jar was sealed with an O-ring, evacuated, and filled with argon. The mixture was ball milled at a speed of 150r / min and a milling time of 2h to obtain a uniformly mixed composite powder.

[0094] Step 2:

[0095] Weigh out 23.75g of alloy powder and 2.5g of composite powder, and load them into a high-strength graphite mold in the order of alloy powder-composite powder-alloy powder. Sinter the mixture in a hot-pressing sintering furnace (ZT-40-20Y) manufactured by Shanghai Chenhua Electric Furnace Co., Ltd. The main sintering process parameters are: vacuum degree 3-4Pa, sintering pressure 25MPa, automatic heating during hot-pressing sintering, heating current 0.25KA; automatic heating: from room temperature to 1070℃, i.e., from room temperature to 300℃, heating rate 5-10℃ / min; 300-900℃, heating rate 10-15℃ / min; 900-1000℃, heating rate 45-50℃ / min; 1000-1070℃, heating rate 3-8℃ / min; hold at 1070℃ for 120min, and then cool to room temperature with the furnace.

[0096] The sintered body of Example 4 was mechanically cut into 15×15×8mm wear samples. The samples were immersed in a solution of 98% concentrated sulfuric acid: methanol: lubricating oil (HFV-vacuum pump oil) = 1:1:8 for 24 hours. After immersion, the samples were removed and excess solution on the surface was removed with oil-absorbing paper. The surface of the samples was kept in a complex acidic state. The treated samples were subjected to friction and wear tests using an MFT-R4000 high-speed reciprocating friction and wear tester. The friction frequency was 3Hz, the wear material was GCr15 (hardness 240HV), the wear load was 30N, and the friction stroke was 2.5mm.

[0097] Example 5

[0098] The specific operating steps in this embodiment are the same as those in Embodiment 4, except that the selected raw material powder is Al powder.

[0099] Example 6

[0100] The specific operation steps in this embodiment are the same as those in embodiment 4, except that the selected raw material powder is alloy powder, that is, the alloy powder prepared in step 1.

[0101] Comparative Example 1

[0102] The comparative example follows the same operating steps as Example 1, but without a composite layer; only a single layer of alloy powder is used. Specifically, 50g of Fe, Mn, Al, Ni, C, and Ti powder (in mass fractions of Fe:Mn:Al:Ni:C:Ti = 56.8:25:9:8:1:0.2) is weighed and sintered. Specific sintering process parameters are as follows: vacuum degree 3-4 Pa, sintering pressure 25 MPa, automatic heating during hot pressing, heating current 0.25 kA; automatic heating: from room temperature to 1070℃ (i.e., from room temperature to 300℃, heating rate 5-10℃ / min); 300-900℃, heating rate 10-15℃ / min; 900-1000℃, heating rate 45-50℃ / min; 1000-1070℃, heating rate 3-8℃ / min; holding at 1070℃ for 120 min, then cooling to room temperature in the furnace.

[0103] The composite material prepared in Comparative Example 1 was mechanically cut into samples of a certain size. Following the specific operation of the experimental polishing, the samples were first polished on sandpaper and then polished on a polishing machine. The microstructure and phase composition of the polished samples were observed and analyzed by a VEGAⅡXMU scanning electron microscope and a Bruker D2 PHASER Gen2 X-ray diffractometer, respectively.

[0104] from Figure 1 (a) It can be seen that, in addition to the gray phase, black dots are also uniformly distributed in the microstructure of the composite material of Comparative Example 1. Figure 1 (c) shows the XRD patterns of the bulk composite materials of Comparative Example 1 and Example 3. As can be seen from the figure, the XRD diffraction pattern of the composite material of Example 3 contains Austenite phase and B2-NiAl phase. This indicates that the Austenite phase with good plasticity and toughness ensures that the composite material has a certain toughness, while B2-NiAl has a high Young's modulus (235 GPa) and thermal conductivity (about 76 W / (m·k)), which can improve the composite material's resistance to deformation and effectively improve its thermal conductivity.

[0105] The specific testing methods are the same as in Example 1. The macroscopic hardness of the bulk composite material prepared in Comparative Example 1 was measured to be 49.2 HRC, and the microhardness was 260.3 HV. The coefficient of friction under simulated complex acidic conditions was tested to be 0.183. Figure 2 As can be seen in (a), there is material peeling on the surface of the wear surface of the block composite material, and its wear mechanism is micro-peeling.

[0106] The macroscopic hardness of the bulk composite material prepared in Example 1 was measured to be 52.8 HRC, which is about 7.32% higher than that of Comparative Example 1. The coefficient of friction under simulated low-sulfur complex acidic conditions was 0.175, which is about 4.4% lower than that of Comparative Example 1.

[0107] The macroscopic hardness of the bulk composite material prepared in Example 2 was measured to be 53.9 HRC, which is about 9.55% higher than that of Comparative Example 1. The coefficient of friction under simulated low-sulfur complex acidic conditions was 0.076, which is about 58.5% lower than that of Comparative Example 1.

[0108] The macroscopic hardness of the bulk composite material prepared in Example 3 was measured to be 58.6 HRC, which is about 19.11% higher than that of Comparative Example 1. The coefficient of friction under simulated low sulfur complex acidic conditions was 0.052, which is about 71.6% lower than that of Comparative Example 1.

[0109] The macroscopic hardness of the bulk composite material prepared in Example 4 was measured to be 51.2 HRC, which is about 4.07% higher than that of Comparative Example 1. The coefficient of friction under simulated low sulfur complex acidic conditions was 0.180, which is about 1.6% lower than that of Comparative Example 1.

[0110] The macroscopic hardness of the bulk composite material prepared in Example 5 was measured to be 52.6 HRC, which is about 6.91% higher than that of Comparative Example 1. The coefficient of friction under simulated low-sulfur complex acidic conditions was 0.102, which is about 44.3% lower than that of Comparative Example 1.

[0111] The macroscopic hardness of the bulk composite material prepared in Example 6 was measured to be 55.2 HRC, which is about 12.20% higher than that of Comparative Example 1. The coefficient of friction under simulated low sulfur complex acidic conditions was 0.070, which is about 61.7% lower than that of Comparative Example 1.

[0112] like Figure 3 As shown, the microhardness of Examples 1-6 shows a trend of gradually increasing from the upper alloy layer and the lower alloy layer to the composite layer. Specific data are shown in Table 1.

[0113] Table 1. Specific data on the microhardness variation of bulk composite materials.

[0114]

[0115] The bulk composite material of Example 3 was processed into samples for scanning electron microscopy and XRD analysis. Figure 1 (b) It can be seen that in the microstructure of the composite material, AlN is uniformly distributed in the layers, with a height of approximately 92 μm, and there is a good metallurgical bonding transition between the upper alloy layer, the composite layer, and the lower alloy layer. Figure 2As can be seen in (b), the worn surface is relatively smooth, with a relatively smooth lubricating film on the surface, and the material peeling phenomenon is relatively small. Figure 2 (a) Significantly reduced.

[0116] Figure 4 (a) is an EDS analysis diagram of the self-lubricating film region of the composite material prepared in Example 3 under complex acidic conditions. It can be seen from the figure that sulfur element is present in the lubricating film region, indicating that the material can reduce the friction coefficient by forming a self-lubricating film on the wear surface with the help of a sulfur-containing atmosphere.

[0117] Figure 4 (b) is the Raman spectrum of the composite material prepared in Example 3 under complex acidic conditions. It can be seen from the figure that the structure of Mn2O3 is mostly a two-dimensional layered structure, and the loose and porous scaly structure of FeS is conducive to storing lubricating oil, thereby improving the boundary lubrication characteristics.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite material for a cylinder head component of a diesel engine, characterized by, The composite material comprises an upper alloy layer, a lower alloy layer, and a composite layer between the upper alloy layer and the lower alloy layer, the macro hardness of the composite material is 51.2-58.6 HRC, and the friction coefficient under simulated low-sulfur complex acidic working conditions is 0.052-0.180; The preparation method of the composite material comprises: Step 1: weighing Fe, Mn, Al, Ni, C and Ti powders, ball milling and uniformly mixing to obtain alloy powder, weighing AlN powder and raw material powder, ball milling and uniformly mixing to obtain composite powder, Step 2: filling a layer of alloy powder into the graphite mold to form a first layer of alloy powder, then filling the composite powder, and finally filling a layer of alloy powder to form a second layer of alloy powder, and obtaining a blocky composite material through vacuum hot pressing sintering; In step 1, the mass fraction of Fe:Mn:Al:Ni:C:Ti is 56.8:25:9:8:1:0.2; In step 1, the raw material powder is Fe powder, Al powder or the alloy powder; the mass fraction ratio of the AlN powder and the raw material powder in step 1 is 1:9; In step 2, the mass of the composite powder accounts for 1-5% of the total mass of the first layer of alloy powder, the composite powder and the second layer of alloy powder, and the mass fraction ratio of the first layer of alloy powder and the second layer of alloy powder is 1:

1.

2. The composite material for diesel engine cylinder head parts according to claim 1, characterized by, In step 2, the first layer of alloy powder is filled and compacted by cold pressing first, then the composite powder is sieved into the graphite mold through the double-screen device, and finally the second layer of alloy powder is filled and compacted by cold pressing.

3. The composite material for diesel engine cylinder head parts according to claim 2, characterized by, The double-screen device comprises an upper screen mechanism on the upper side and a lower screen mechanism on the lower side, the upper screen mechanism and the lower screen mechanism are coaxially arranged, and the screen hole shapes of the upper screen mechanism and the lower screen mechanism are different; The upper screen mechanism comprises an upper fixed ring (1), an upper screen (2) and an upper ejection ring (3) arranged coaxially; The upper fixed ring (1) is horizontally arranged, The upper screen (2) is made of rubber cloth material, the hole shape is circular, is located in the inner cavity of the upper fixed ring (1), and the outer edge of the upper screen (2) is fixedly connected with the inner edge of the upper fixed ring (1), The upper ejection ring (3) is horizontally arranged below the upper screen (2), is used for lifting the upper screen (2) upward when the upper fixed ring (1) is pressed downward, and thus the hole diameter of the upper screen (2) is enlarged, so that the agglomerated composite powder on the upper screen (2) is dispersed and falls down.

4. The composite material for diesel engine cylinder head parts according to claim 3, characterized by, The lower screen mechanism comprises a lower fixed ring (4), a lower screen (5) and a lower ejection ring (6) arranged coaxially; The lower fixed ring (4) is horizontally arranged, The lower screen (5) is made of rubber cloth material, the hole shape is square, is located in the inner cavity of the lower fixed ring (4), and the outer edge of the lower screen (5) is fixedly connected with the inner edge of the lower fixed ring (4), The lower ejection ring (6) is horizontally arranged below the lower screen (5), is used for lifting the lower screen (5) upward when the lower fixed ring (4) is pushed downward, and thus the hole diameter of the lower screen (5) is enlarged, so that the composite powder on the lower screen (5) which is flattened by the scraper mechanism (8) is sieved into the graphite mold.

5. The composite material for diesel engine cylinder head parts according to claim 4, characterized by, The upper side of the upper ejection ring (3) is provided with a circular groove (7) from top to bottom, the axis of the groove (7) coincides with the axis of the upper ejection ring (3), the groove (7) is used for the extension of the scraper mechanism (8), and the scraper mechanism (8) is used for spreading the composite powder accumulated on the lower screen (5).

6. The composite material for diesel engine cylinder head parts according to claim 5, characterized by, The scraper mechanism (8) comprises: A first vertical rod (9) is vertically arranged, and the lower end of the first vertical rod (9) extends into the groove (7), A lower clamping ring (10) is sleeved on the lower half of the first vertical rod (9), and is used for abutting against the edge of the groove (7) of the upper ejection ring (3), so as to limit the depth of the first vertical rod (9) extending into the groove (7), An upper clamping ring (11) is sleeved on the upper half of the first vertical rod (9), A push rod (12) is horizontally arranged, one end of the push rod (12) is sleeved on the upper half of the first vertical rod (9) and is arranged on the upper side of the upper clamping ring (11), so that the upper clamping ring (11) supports the push rod (12), A scraper (13) is vertically arranged, the upper end of the scraper (13) is fixedly connected with the push rod (12), and the lower end of the scraper (13) extends downward and extends into the inner cavity of the upper ejection ring (3), A second vertical rod (14) is vertically arranged, and the lower end of the second vertical rod (14) is fixedly connected with the other end of the push rod (12), and is used for cooperating with the first vertical rod (9) to rotate the scraper (13) around the axis of the upper ejection ring (3), so as to spread the composite powder accumulated on the lower screen (5).

Images