Method for improving wear resistance of aluminum alloy piston and prepared piston part

Abstract

The invention discloses a method for improving wear resistance of an aluminum alloy piston and a prepared piston part, and belongs to the technical field of machine manufacturing. According to the technical scheme, the surface of the piston is subjected to coating treatment through a physical vapor deposition technology to prepare the aluminum alloy piston with good wear resistance, the advantages of three materials of AlMo, AlMoB and MoO3 and a multi-layer composite structure are combined, an AlMo layer is prepared between a coating and a workpiece base body through a sputtering method, the adhesion performance of the coating and the base body is enhanced, and the wear resistance of the aluminum alloy piston is improved. And then the AlMoB coating and the MoO3 coating are deposited through a radio frequency reactive sputtering method, so that the physical property difference between the coatings and a base material is relieved, the hardness and strength of the coatings are improved, the antifriction wear resistance and the high temperature resistance of the aluminum alloy piston are improved, and the service life of the aluminum alloy piston of the engine is effectively prolonged.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, specifically relating to a method for improving the wear resistance of aluminum alloy pistons and the piston parts prepared therefrom. Background Technology

[0002] As a core moving component of an engine, the performance of aluminum alloy pistons directly affects the engine's efficiency, reliability, and service life. Because pistons operate under harsh conditions of high temperature, high pressure, and high-speed reciprocating motion, critical parts such as the piston skirt and ring grooves often face severe frictional and adhesive wear problems, leading to reduced engine power, increased oil consumption, and even cylinder scoring. Therefore, improving the wear resistance of aluminum alloy pistons is one of the key technical challenges in enhancing the overall performance and durability of engines.

[0003] Currently, surface treatment technologies such as anodizing, electroplating, thermal spraying, and physical vapor deposition are commonly used to improve the wear resistance of aluminum alloy pistons. While anodizing and electroplating can improve surface properties to some extent, the resulting coatings have limited adhesion to the substrate, and the coatings themselves may contain defects such as porosity, making them prone to peeling under long-term alternating loads. Thermal spraying produces thicker coatings, but the bonding strength and significant differences in physical properties (such as coefficient of thermal expansion and modulus of elasticity) between the coating and the substrate can lead to cracking or even failure of the coating under thermal cycling or mechanical impact.

[0004] Physical vapor deposition (PVD) technology, especially sputtering, has shown great potential in the field of surface modification of precision parts due to its advantages such as low processing temperature, uniform and dense coatings, and good adhesion to the substrate. However, single-component PVD coatings (such as single nitride, carbide, or oxide coatings) often fail to simultaneously meet the comprehensive requirements of high hardness, toughness, and low coefficient of friction. For example, high-hardness ceramic coatings may be brittle and prone to cracking under impact loads; while soft coatings with good friction-reducing properties may lack sufficient hardness and have limited wear resistance.

[0005] Furthermore, directly depositing functional coatings on aluminum alloy substrates faces a key challenge: the physical properties (such as coefficient of thermal expansion and elastic modulus) of aluminum alloys differ significantly from those of high-performance ceramic or cermet coatings. This can easily lead to insufficient interfacial adhesion between the coating and the substrate, resulting in premature peeling during service. Simultaneously, the columnar crystal structure commonly found in PVD coatings can become a pathway for crack propagation and corrosive media penetration, weakening the long-term stability of the coating.

[0006] Therefore, developing a multi-layer composite coating structure and corresponding preparation process to achieve a strong and tough bond between the coating and the aluminum alloy piston substrate, and to synergistically improve the hardness, wear resistance and friction reduction and lubrication performance of the coating surface, while avoiding the degradation of the piston substrate's microstructure and properties due to excessively high processing temperatures, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] This invention provides a method for improving the wear resistance of aluminum alloy pistons and a piston part prepared therefrom. It can increase the hardness of piston material, enhance the adhesion between the piston surface deposited coating and the substrate, and reduce the difference in physical properties between the deposited coating and the substrate material, thereby improving the friction reduction and wear resistance of aluminum alloy pistons and effectively increasing the service life of pistons.

[0008] The technical solution of this invention is as follows: In the first aspect, a method for improving the wear resistance of aluminum alloy pistons is disclosed. After the aluminum alloy piston blank is smelted and refined, cast, heat treated, rough machined, fine machined, deburred and cleaned, an AlMo / AlMoB / MoO3 composite coating is deposited by reactive radio frequency sputtering. Two Al sputtering targets and two Mo sputtering targets are used during the deposition. Specifically, the following steps are included: (1) Casting of aluminum alloy piston blanks: Piston blank melting → casting → solidification and demolding → heat treatment; (2) Machining of aluminum alloy pistons: rough machining of piston base → semi-finishing → finishing → deburring → cleaning to remove surface oil; (3) Surface treatment of aluminum alloy piston parts: Put the parts into alcohol, ultrasonically clean them to remove surface impurities and attachments, blow them dry, and put them into a PVD composite coating machine. (4) Ion cleaning of piston parts surface: pulse bias voltage adjusted to -450V, duty cycle 0.35, Ar gas pressure 1.5-2.0Pa, temperature 265℃, Ar + Ion cleaning for 18-20 minutes; (5) Deposit AlMo layer: Ar gas pressure is adjusted to 0.5-0.6 Pa, flow rate is 40-50 sccm, pulse bias voltage is -235 V, deposition temperature is 250-255 ℃, Al target power is turned on at 80 W, Mo target power is 65 W, and AlMo coating is deposited for 15-20 min. (6) Reactive sputtering of AlMoB layer: Ar flow rate is 80-90 sccm, pulse bias voltage is -225V, deposition temperature is 240-245℃, Al target power is 100W, Mo target power is 85W, B2H6 gas flow rate is 10-15 sccm, reactive sputtering deposition of AlMoB coating is 25-30min. (7) Reactive sputtering of MoO3 layer: turn off Al target and B2H6 gas, Ar flow rate is 60-70 sccm, pulse bias voltage is -210V, deposition temperature is 190-200℃, Mo target power is 70W, turn on O2 gas flow rate is 20-25 sccm, and reactive sputtering deposits MoO3 coating for 20-25 min. (8) Post-treatment: Turn off the power supply, ion source and gas source of each target, let the room temperature drop to below 100℃, take out the sample, and the coating is finished.

[0009] Preferably, the aluminum alloy piston base material is one of the national standard grades ZL109, ZL108 and A390.

[0010] Preferably, the ultrasonic cleaning time in step (3) is 30 min, and high-purity nitrogen is used for drying.

[0011] Preferably, in step (3), a vacuum of 5.0 × 10⁻⁶ is drawn in the composite coating machine. -3 Pa, heat to 320℃, and hold for 20 minutes.

[0012] Preferably, in step (6), the boron atom content introduced by the B2H6 gas reaction in the AlMoB layer accounts for 13-17 at.% of the total metal atoms.

[0013] Secondly, the piston part prepared by the method is disclosed. The piston part has the following structure: a composite coating consisting of an AlMo layer, an AlMoB layer, and a MoO3 layer sequentially distributed outward from the surface of the part substrate.

[0014] Compared with the prior art, the present invention has the following advantages: This invention presents a method for improving the wear resistance of aluminum alloy pistons using reactive radio frequency sputtering. It combines the advantages of boride coatings, PVD methods, oxide coatings, and multilayer composite structures. An AlMo layer is sputtered between the boride coating and the substrate to mitigate the difference in physical properties between the coating and the substrate, enhancing adhesion and providing a strong supporting matrix and good bonding performance for the subsequent AlMoB / MoO3 composite coating. Simultaneously, the interlayer interface of this AlMo / AlMoB / MoO3 multilayer composite coating structure prevents the growth of columnar crystals in the coating, hindering crack and defect propagation and improving the coating's hardness, toughness, and impact resistance. Furthermore, the AlMoB coating in this AlMo / AlMoB / MoO3 multilayer composite coating improves the surface material's hardness, strength, and wear resistance; the surface MoO3 coating improves the surface friction coefficient, enhancing the material's friction-reducing and lubricating properties. The preparation of this composite coating improves the overall performance of the engine's aluminum alloy piston, effectively enhancing the workpiece's performance and service life.

[0015] The method for improving the wear resistance of aluminum alloy pistons employed in this invention, compared to traditional aluminum alloy piston substrates, enhances the adhesion between the coating and the substrate, reduces friction and adhesion during operation, and increases surface hardness by more than six times. The coefficient of friction of the composite coating prepared by this invention is approximately 0.22-0.24, and the coating wear rate can reach 2.32-2.37×10-6 mm3 / N·m. Because the coating treatment uses reactive radio frequency sputtering, it extends the service life of engine pistons and reduces maintenance and upkeep costs. Furthermore, since the preparation process temperature can be controlled below 300℃, it does not cause degradation of the substrate's microstructure, and the surface dimensions and shape accuracy remain unaffected. No further grinding or reprocessing is required after treatment, making it a suitable final processing method for aluminum alloy piston parts. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the surface structure of the aluminum alloy piston obtained in Embodiment 1 of the present invention.

[0017] In the figure: 1. Component substrate; 2. AlMo layer; 3. AlMoB layer; 4. MoO3 layer.

[0018] Figure 2 This is a morphological image of the AlMo / AlMoB / MoO3 composite coated part prepared in Example 1 of the present invention.

[0019] Figure 3 This is a scratch morphology image of the AlMo / AlMoB / MoO3 composite coated part prepared in Example 1 of this invention.

[0020] Figure 4 This is a surface wear mark morphology image of the AlMo / AlMoB / MoO3 composite coated part prepared in Example 1 of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of this invention.

[0022] Example 1 A method for improving the wear resistance of aluminum alloy pistons, wherein the substrate material of the aluminum alloy piston part 1 is A390, and the aluminum alloy piston blank is subjected to melting and refining, casting, heat treatment, rough machining, fine machining, deburring and cleaning, and then depositing an AlMo / AlMoB / MoO3 composite coating by reactive radio frequency sputtering method, using 2 Al sputtering targets and 2 Mo sputtering targets during deposition.

[0023] Specifically, the following steps are included: (1) Casting of aluminum alloy piston blanks: The A390 aluminum alloy ingot is heated to a molten state (approximately 740°C) in a melting furnace. Add hexachloroethane refining agent at a rate of 0.5% of the aluminum alloy ingot mass. Introduce argon gas to degas and remove slag, thereby removing hydrogen and oxide inclusions from the molten metal and preventing porosity and shrinkage in the casting. The molten aluminum is poured into a preheated metal mold at a preheating temperature of 280°C. The molten aluminum cools and solidifies in the mold, and the piston blank is removed. The piston blank is heated to about 500℃, held for 5 hours, and then quickly quenched in water. The quenched piston was kept at 150℃ for 6 hours until the material reached a stable state.

[0024] (2) Machining of aluminum alloy pistons: Rough datum machining (using the top of the piston inner cavity as the rough datum, machining the fine datum—stop and end face, roughness Ra 3.2μm) → Rough machining of the outer circle (clamping with the stop and end face as the datum, rough turning the piston outer circle, ring land, and ring groove, leaving a machining allowance of 0.7mm) → Pin hole machining (tolerance grade H6, Ra 0.8 μm) → Ring groove machining (tolerance grade H7, Ra 1.6 μm) → Skirt profile machining (Ra 0.8μm) → Weight removal and dynamic balancing → Deburring and cleaning.

[0025] (3) Surface treatment of aluminum alloy pistons: The parts are ultrasonically cleaned in alcohol for 30 minutes to remove surface impurities and other attachments, dried with high-purity nitrogen, and quickly loaded into a PVD composite coating machine and vacuumed to 5.0×10. -3 Pa, heat to 320℃, and hold for 20 minutes; (4) Ion cleaning of piston surface: Pulse bias voltage adjusted to -450V, duty cycle 0.35, Ar gas pressure 1.5Pa, temperature 265℃, Ar + Ion cleaning for 18 minutes; (5) Deposition of AlMo layer 2: Ar gas pressure is adjusted to 0.5 Pa, flow rate is 40 sccm, pulse bias voltage is -235 V, deposition temperature is 250 °C, Al target power is turned on at 80 W, Mo target power is 65 W, and AlMo coating is deposited for 15 min. (6) Reactive sputtering of AlMoB layer 3: Ar flow rate 80 sccm, pulse bias -225V, deposition temperature 240℃, Al target power 100W, Mo target power 85W, B2H6 gas flow rate 10 sccm, reactive sputtering deposition of AlMoB coating for 25 min; in AlMoB layer 3, the boron atom content introduced by the reaction of B2H6 gas accounts for 14 at.% of the total metal atoms. (7) Reactive sputtering of MoO3 layer 4: Al target and B2H6 gas are turned off, Ar flow rate is 60sccm, pulse bias voltage is -210V, deposition temperature is 190℃, Mo target power is 70W, O2 gas flow rate is turned on at 20sccm, and reactive sputtering deposition of MoO3 coating is carried out for 20min. (8) Post-treatment: Turn off the power supply, ion source and gas source of each target, let the room temperature drop to below 100℃, take out the sample, and the coating is finished.

[0026] like Figure 1 The wear-resistant aluminum alloy piston obtained in this embodiment has the following structure: a composite coating consisting of an AlMo layer 2, an AlMoB layer 3, and a MoO3 layer 4, which are sequentially distributed outward from the surface of the component substrate 1.

[0027] The microhardness of the part with the AlMo / AlMoB / MoO3 composite coating prepared in this embodiment reaches HV1540, which is more than 6 times higher than the surface hardness (HV210) of the MoS2 lubricating coating prepared alone for traditional aluminum alloy pistons; the coating thickness is 1.05μm, the surface roughness reaches Ra 45nm, and the surface morphology is as follows. Figure 2 As shown. The coating adhesion strength is 85-92 N, which is nearly 4 times higher than the adhesion strength (22-30 N) of traditional piston friction-reducing MoS2 lubricating coating. The adhesion scratch morphology of this composite coating is as follows. Figure 3 As shown, although the applied force is large at the end of the scratch test, coating residue still remains, indicating a significant improvement in coating adhesion. Under the same friction test conditions (HRT multifunctional friction tester, reciprocating linear motion, grinding balls made of bearing steel with a surface hardness of HRC50-56, applied load of 60N, sliding speed of 10mm / s, and grinding time of 30min), the coefficient of friction of the composite coating prepared in this invention is approximately 0.22-0.24, which is more than 50% lower than that of the uncoated aluminum alloy (coefficient of friction approximately 0.56-0.64). The coating wear rate is approximately 2.32-2.37×10⁻⁶. -6 mm 3 / N·m, compared with the uncoated part, the wear rate is reduced by about 87-92%, and the surface wear morphology of the coated part is as follows. Figure 4 As shown, this indicates that the composite coating has excellent overall performance and still leaves residues after prolonged friction.

[0028] Example 2 A method for improving the wear resistance of aluminum alloy pistons, wherein the substrate material of the aluminum alloy piston part 1 is ZL109, and the aluminum alloy piston blank is subjected to melting and refining, casting, heat treatment, rough machining, fine machining, deburring and cleaning, and then deposited with AlMo / AlMoB / MoO3 composite coating by reactive radio frequency sputtering method, using 2 Al sputtering targets and 2 Mo sputtering targets during deposition.

[0029] Specifically, the following steps are included: (1) Casting of aluminum alloy piston blanks: The ZL109 aluminum alloy ingot is heated to a molten state (approximately 750°C) in a melting furnace. Add hexachloroethane refining agent at a rate of 0.3% of the aluminum alloy ingot mass. Introduce argon gas to degas and remove slag, thereby removing hydrogen and oxide inclusions from the molten metal and preventing porosity and shrinkage in the casting. The molten aluminum is poured into a preheated metal mold at a preheating temperature of 300°C. The molten aluminum cools and solidifies in the mold, and the piston blank is removed. The piston blank is heated to about 500℃, held for 6 hours, and then quickly quenched in water. The quenched piston was kept at 200℃ for 6 hours until the material reached a stable state.

[0030] (2) Machining of aluminum alloy pistons: Rough datum machining (using the top of the piston inner cavity as the rough datum, machining the fine datum—stop and end face, roughness Ra 3.2μm) → Rough machining of the outer circle (clamping with the stop and end face as the datum, rough turning the piston outer circle, ring land, and ring groove, leaving a machining allowance of 0.5mm) → Pin hole machining (tolerance grade H6, Ra 0.4 μm) → Ring groove machining (tolerance grade H7, Ra 1.6 μm) → Skirt profile machining (Ra 0.8 μm) → Weight removal and dynamic balancing → Deburring and cleaning.

[0031] (3) Surface treatment of aluminum alloy pistons: The parts are ultrasonically cleaned in alcohol for 30 minutes to remove surface impurities and other attachments, dried with high-purity nitrogen, and quickly loaded into a PVD composite coating machine and vacuumed to 5.0×10. -3 Pa, heat to 320℃, and hold for 20 minutes; (4) Ion cleaning of piston surface: Pulse bias voltage adjusted to -450V, duty cycle 0.35, Ar gas pressure 2.0Pa, temperature 265℃, Ar + Ion cleaning for 20 minutes; (5) Deposition of AlMo layer 2: Ar gas pressure is adjusted to 0.6 Pa, flow rate is 50 sccm, pulse bias voltage is -235 V, deposition temperature is 255 °C, Al target power is turned on at 80 W, Mo target power is 65 W, and AlMo coating is deposited for 20 min. (6) Reactive sputtering of AlMoB layer 3: Ar flow rate 90 sccm, pulse bias -225V, deposition temperature 245℃, Al target power 100W, Mo target power 85W, B2H6 gas flow rate 15 sccm, reactive sputtering deposition of AlMoB coating for 30 min; in AlMoB layer 3, the boron atom content introduced by the reaction of B2H6 gas accounts for 16 at.% of the total metal atoms. (7) Reactive sputtering of MoO3 layer 4: Al target and B2H6 gas are turned off, Ar flow rate is 70 sccm, pulse bias voltage is -210V, deposition temperature is 200℃, Mo target power is 70W, O2 gas flow rate is turned on at 25 sccm, and reactive sputtering is used to deposit MoO3 coating for 25 min. (8) Post-treatment: Turn off the power supply, ion source and gas source of each target, reduce the room temperature to below 80°C, take out the sample, and the coating is finished.

[0032] The surface microhardness of the part with the AlMo / AlMoB / MoO3 composite coating prepared in this embodiment reaches HV1470, which is 6 times higher than the surface hardness (HV210) of the MoS2 lubricating coating prepared by a traditional aluminum piston alone; the bonding strength is 87-97N, which is nearly 4 times higher than the bonding strength (22-30N) of the traditional MoS2 lubricating coating; the coating thickness is 1.01μm, and the coating surface roughness reaches Ra48nm.

[0033] Although the present invention has been described in detail by way of preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method of improving the wear resistance of an aluminum alloy piston, characterized by, After the aluminum alloy piston blank is smelted and refined, cast, heat treated, roughly machined, finely machined, deburred and cleaned, an AlMo / AlMoB / MoO3 composite coating is deposited on the aluminum alloy piston blank by a reactive radio frequency sputtering method; two Al sputtering targets and two Mo sputtering targets are used during the deposition; Specifically comprising the following steps: (1) Casting of the aluminum alloy piston blank: smelting of the piston blank, casting, solidification and demolding, and heat treatment; (2) Machining of the aluminum alloy piston: rough machining of the piston base, semi-finishing, finishing, deburring, and cleaning to remove surface oil; (3) Surface treatment of the aluminum alloy piston part: the part is placed in alcohol, ultrasonic cleaning is performed to remove surface impurities and attachments, the part is dried, and the part is loaded into a PVD composite coating machine; (4) Ion cleaning of piston part surface: pulse bias is adjusted to -450V, duty ratio 0.35, Ar pressure 1.5-2.0 Pa, temperature 265℃, Ar + ion cleaning 18-20 min; (5) Deposition of the AlMo layer: Ar gas pressure is adjusted to 0.5-0.6 Pa, the flow rate is 40-50 sccm, the pulsed bias voltage is -235 V, the deposition temperature is 250-255℃, the Al target power is 80 W, the Mo target power is 65 W, and the AlMo coating is deposited for 15-20 min; (6) Reactive sputtering of the AlMoB layer: Ar flow rate is 80-90 sccm, the pulsed bias voltage is -225 V, the deposition temperature is 240-245℃, the Al target power is 100 W, the Mo target power is 85 W, the B2H6 gas flow rate is 10-15 sccm, and the AlMoB coating is deposited by reactive sputtering for 25-30 min; (7) Reactive sputtering of the MoO3 layer: the Al target and the B2H6 gas are turned off, Ar flow rate is 60-70 sccm, the pulsed bias voltage is -210 V, the deposition temperature is 190-200℃, the Mo target power is 70 W, the O2 gas flow rate is 20-25 sccm, and the MoO3 coating is deposited by reactive sputtering for 20-25 min; (8) Post-treatment: the target power, the ion source and the gas source are turned off, the chamber temperature is reduced to below 100℃, the sample is taken out, and the coating is completed.

2. The method of improving the wear resistance of an aluminum alloy piston of claim 1 wherein, The aluminum alloy piston base material is one of ZL109, ZL108 and A390 according to the national standard.

3. The method of improving the wear resistance of an aluminum alloy piston of claim 1 wherein, The ultrasonic cleaning time in step (3) is 30 min, and high-purity nitrogen is used for drying.

4. The method of improving the wear resistance of an aluminum alloy piston of claim 1 wherein, Step (3) in a composite coating machine, vacuum to 5.0 x 10 -3 Pa, heated to 320℃, and kept for 20 min.

5. The method of improving the wear resistance of an aluminum alloy piston of claim 1 wherein, In step (6), the boron atom content introduced by the B2H6 gas reaction in the AlMoB layer accounts for 13-17 at.% of the total metal atom content.

6. The piston part prepared according to the method of any one of claims 1 to 5, characterized in that The piston part has the following structure: the composite coating of the AlMo layer, the AlMoB layer and the MoO3 layer is sequentially arranged on the surface of the part base.

Images