CN116288340B - Copper alloy-spheroidal graphite cast iron bimetal wear-resistant antifriction plate and preparation method thereof - Google Patents

Abstract

The present invention discloses a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate and a preparation method thereof. A high-energy-density laser beam is used to heat and melt copper alloy powder on the surface of ductile iron and rapidly solidify to form a copper alloy-ductile iron bimetallic plate. Granular graphite powder is then melted into the copper alloy layer by a process combining laser cladding and laser remelting to form a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate with uniform composition. The core technology of the present invention includes the composition and preparation process of a copper-based composite layer as a wear-resistant and friction-reducing layer and a copper alloy-ductile iron connection technology. The wear-resistant and friction-reducing copper alloy layer on the surface of ductile iron provided by the present invention has a surface hardness of 191.3-243.0HV _0.3 , a dry friction coefficient of 0.028-0.059, a relative wear resistance of 3.5-4.6, and a shear strength of 184-201Mpa.

Description

Copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate and preparation method thereof

Technical Field

The invention relates to a copper alloy-ductile iron bimetallic wear-resistant and anti-friction plate and a preparation method thereof. A high-energy-density laser beam is used to heat and melt copper alloy powder on the surface of ductile iron and rapidly solidify the copper alloy-ductile iron bimetallic plate. Granular graphite powder is then melted into the copper alloy layer through a process combining laser cladding and laser remelting to form a copper alloy-ductile iron bimetallic wear-resistant and anti-friction plate with uniform composition. The invention belongs to the field of materials science and engineering.

Background Art

Copper alloy-steel bimetallic wear-resistant and anti-friction plate is made by melting a layer of wear-resistant and anti-friction layer on the surface of steel through material processing technology. This structure of copper alloy-steel bimetallic wear-resistant and anti-friction plate can comprehensively play the advantages of two materials, which not only meets the requirements of friction pair components for material matching, structure and functionality, but also improves the comprehensive performance of components. It is widely used in friction pair components of transportation machinery, engineering machinery and hydraulic systems. At present, the processing technologies of copper alloy-steel bimetallic wear-resistant and friction-reducing plate materials include fusion welding, gas welding, brazing, explosion welding, thermal spraying, solid diffusion welding, casting, mechanical inlay, vapor deposition, powder metallurgy sintering and rolling composite methods, etc., and many invention patents have been applied for, such as Chinese invention patents CN201010574604.9, CN201210234085.0, CN201310712523.4, CN201510789408.6, CN201610320678.7, CN201610502247.2, and CN201711008255.2. Copper alloys used as wear-resistant and friction-reducing layers include tin bronze, lead bronze, aluminum bronze, and various copper-based composite materials, such as Chinese invention patents CN201610320678.7, CN201510789408.6, CN201010226578.0, CN201910733305.6, and CN102528048B. In addition, there are many literature reports that copper-based composite materials are prepared as wear-resistant and friction-reducing layers by in-situ or external addition of second phases such as particles, fibers, and whiskers with copper alloy as the main body. The steel used as the matrix material is mostly 45# high-quality carbon steel and alloy steel such as 40CrNiMoA.

All engineering fields and any occasions with mechanical equipment are inseparable from hydraulic systems. In recent years, with the rapid development of my country's industrial equipment, higher requirements have been put forward for the friction pair components of hydraulic systems. Among them, the high-pressure plunger pump is the core component of high-end hydraulic equipment and is called the "heart" of the hydraulic system. Its working principle is to use a motor to drive the energy conversion element to output a controllable high-pressure fluid to the outside, realize the action of the hydraulic actuator, and complete the control of linear motion or rotational motion. The core components of the energy conversion element of the high-pressure plunger pump are friction pair components such as the swing seat, the distribution plate and the cylinder body. Due to the increased friction loss of the friction pair components, the hydraulic pump will be induced to heat abnormally. The temperature is too high, causing the hydraulic system components to expand, resulting in the destruction of the component matching clearance and the jamming of the hydraulic valve. For this reason, on August 30, 2018, one of the 35 "stuck neck" technologies reported by Science and Technology Daily was "the high-pressure plunger pump is a thorn in the throat of my country's equipment manufacturing industry. To achieve a technological breakthrough in high-pressure plunger pump products, it is necessary to first achieve a breakthrough in important energy conversion component technology." High-pressure plunger pumps are developing towards high efficiency, long life, low noise and miniaturization, especially high-pressure plunger pumps with rated pressure higher than 35MPa and speed greater than 1800r/min, which put forward higher requirements on important technical indicators such as volumetric efficiency of plunger pump cylinder and wear resistance and fatigue life of core friction pair components. Although the steel matrix in the copper alloy-steel bimetallic wear-resistant and anti-friction plate has good mechanical properties, when subjected to flow vibration and pressure pulsation caused by liquid resistance for a long time, the lack of impact resistance and dimensional stability will affect the fit between the contact surfaces, reduce the sealing, and cause failures such as insufficient flow, low pressure, and overheating of components and jamming; the increase in vibration acceleration will also cause the loosening of related fixing components, induce resonance, and accelerate the damage of the hydraulic system. Ductile iron has good casting performance, low linear expansion coefficient, and is easy to machine. It also has high strength, plasticity and toughness, wear resistance, heat resistance, shock absorption and mechanical impact resistance, high or low temperature resistance, corrosion resistance and dimensional stability. Ductile iron is used instead of steel to produce the friction pair components in the plunger pump assembly with high dimensional accuracy, good strength and wear resistance, and can achieve weight reduction and noise reduction. It has attracted much attention from hydraulic system manufacturers and the industry. Copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plates instead of copper alloy-steel bimetallic wear-resistant and friction-reducing plates have higher practical value. For this reason, many universities, research institutes and enterprises have carried out research in this area and published academic papers or applied for invention patents, such as Chinese invention patents CN199110009101.3, CN201911169466.3, CN202011317769.8 and CN202211270663.6. The problems in manufacturing copper alloy-ductile iron bimetallic friction pair components include the following aspects: On the one hand, there are large differences in the physical, chemical and mechanical properties of ductile iron and copper alloy, which affect the interface bonding performance. The traditional sintering method is prone to holes in the interface and it is difficult to achieve tight connection; On the other hand, the use of melting welding or high-temperature processing methods is easy to cause the softening of copper alloy. Copper alloy is subjected to high pressure, friction and high temperature. Under the repeated cycle of alternating stress, the surface of the copper alloy wear-resistant and friction-reducing layer is prone to cracks and local peeling, resulting in reduced wear resistance of the copper alloy as a wear-resistant and friction-reducing layer. Various friction pair components of the plunger pump assembly are used to bear pressure and resist impact. They are both structural parts and functional parts. In addition to having a certain bonding strength, the copper alloy-ductile iron interface of the bimetallic friction pair component must also ensure that the copper alloy prepared on the surface of the ductile iron as a wear-resistant and friction-reducing layer also has anti-fatigue, anti-bite, anti-friction, good thermal conductivity, and is not easy to produce friction and adhesion when the working temperature reaches 300℃. Most of the existing technologies emphasize the interface bonding strength between copper alloy and ductile iron or copper alloy and steel in bimetallic friction pair components, ignoring the performance of copper alloy as a wear-resistant and friction-reducing layer and the impact of thermal effects on the performance of copper alloy during the manufacturing process. Therefore, how to use simple and effective processes and methods to prepare copper alloy-ductile iron bimetallic hydraulic components and extend the service life of hydraulic components is an unshirkable responsibility and task for scientific researchers.

Summary of the invention

The purpose of the present invention is to provide a copper alloy-ductile iron bimetallic wear-resistant and anti-friction plate and a preparation method thereof, wherein a high-energy-density laser beam is used to heat copper alloy powder on the surface of ductile iron to melt and rapidly solidify to form a copper alloy-ductile iron bimetallic plate, and then granular graphite powder is melted into the copper alloy layer through a process combining laser cladding and laser remelting to form a copper alloy wear-resistant and anti-friction layer with uniform composition, thereby constituting a copper alloy-ductile iron bimetallic wear-resistant and anti-friction plate.

The present invention discloses a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate and a preparation method thereof, the core of which lies in: first, the composition and preparation process of the copper-based composite layer as the wear-resistant and friction-reducing layer; second, the copper alloy-ductile iron connection technology. The copper-based composite layer described in the present invention is composed of two parts, one part is an aluminum bronze main body that can form a metallurgical bond with ductile iron, and the other part is a graphite reinforcement phase that improves the surface wear resistance and friction reduction performance and forms a wear-resistant and friction-reducing layer with the copper alloy. The copper alloy-ductile iron connection technology described in the present invention first uses cold welding technology to form a transition layer, and then uses laser technology to form a wear-resistant and friction-reducing layer.

The above-mentioned object of the present invention is achieved as follows: a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate, the base material is ductile iron (grade QT500-7), the specification is plate; the copper alloy is aluminum bronze, the average diameter is 50-150um granular, the aluminum content is 8-10 by mass percentage (Wt/%), the impurity content is ≤0.3, and the rest is copper. The bimetallic plate is composed of multiple layers, the first layer is aluminum bronze; the second layer is a graphite reinforcement phase that improves the surface wear resistance and friction reduction performance and forms a wear-resistant and friction reduction layer with the copper alloy, wherein the graphite is a high-purity component, the average diameter is 50-150um granular, and the surface is coated with a layer of metal nickel. The mixing ratio of the graphite reinforcement phase to the copper alloy powder is, by mass percentage (Wt/%), the graphite reinforcement phase is 2.5-5, and the rest is aluminum bronze powder.

The method for preparing a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate of the present invention comprises the following steps: depositing an aluminum bronze intermediate layer on the surface of the ductile iron by a cold welding method; preparing a graphite reinforcement phase with wear-resistant and friction-reducing properties on the surface of the ductile iron by a process combining laser cladding and laser remelting to form a wear-resistant and friction-reducing layer with the copper alloy; and mechanically strengthening the copper alloy cladding layer by a mechanical vibration process. The method comprises the following steps:

In the first step, the surface of ductile iron is treated mechanically and chemically to remove oil, oxides and level the plate surface;

In the second step, a layer of aluminum bronze intermediate layer is deposited on the surface of the ductile iron by cold welding method. The cold welding process parameters are: power 50-80W, welding time 25-80s, intermediate layer alloy thickness 0.2-0.5mm, and the intermediate layer alloy forms a dense metallurgical bond with the ductile iron surface;

The third step is to use the pre-set powder method to evenly spread the copper alloy powder on the middle layer of the surface of the ductile iron plate to form a pre-set layer with a thickness of 0.8-1.2mm, and perform mechanical compaction treatment, and perform multiple laser cladding on the pre-set copper alloy powder. Use a fiber continuous laser to heat the copper alloy powder to obtain a copper alloy cladding layer on the surface of the ductile iron. The high-energy density fiber continuous laser described in the present invention is optimized to obtain the following process parameters for laser cladding: laser power 1600W, scanning speed 4mm/s, spot diameter 3.5mm, and defocus 30mm. The protective gas is argon, and the gas flow rate is 15L/min;

The fourth step is to mechanically mix the graphite reinforcement phase with the copper alloy powder, and use the pre-powder method to evenly spread the mixed powder on the copper alloy cladding layer on the surface of the ductile iron plate to form a pre-layer with a thickness of 0.8-1.2mm. Mechanical compaction treatment is performed again, and the third step of laser cladding process is repeated. The mixing ratio of the graphite reinforcement phase and the copper alloy powder is 2.5-5 in mass percentage (Wt/%) of the graphite reinforcement phase, and the rest is aluminum bronze powder. According to the designed component ratio, the graphite reinforcement phase and the copper alloy powder are evenly mixed and vacuum ball milled at a ball milling speed of 150r/min for 1h;

The fifth step is to mechanically grind and smooth the copper alloy cladding layer on the surface of the ductile iron;

In the sixth step, the copper alloy cladding layer on the surface of the ductile iron is subjected to mechanical vibration treatment, and finally a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate is formed. The mechanical vibration amplitude is 10 μm, the feed rate is 10 mm/min, and the vibration pressure is 300N.

Ductile iron has a high carbon content and will tend to whiten when exposed to the heat of the laser, forming cracks at the interface of the cladding layer. The present invention adopts a cold welding method to pre-deposit an aluminum bronze intermediate layer on the surface of the ductile iron, which can avoid the appearance of white structure during the subsequent laser cladding process. Aluminum bronze has high strength, hardness and wear resistance. When laser cladding is directly performed on the surface of ductile iron, _Fe3Al2 compounds will precipitate at the interface of the copper alloy _/ ductile iron. Through the transition of the intermediate layer, the mechanical properties of the connection interface can be improved. Adding graphite can improve the thermal conductivity and friction and wear properties of aluminum bronze materials; coating the graphite surface with a layer of metal nickel can effectively improve the formability of laser cladding. Under the heat of the laser, nickel and aluminum bronze locally form aluminum-nickel bronze on the surface of the graphite powder particles, further improving the various properties of the copper alloy cladding layer. The cladding layer obtained by laser cladding is actually a cast structure with loose and coarse structure, and it is inevitable that there will be defects such as pores, inclusions and cracks inside. The copper alloy cladding layer obtained on the surface of ductile iron is subjected to mechanical vibration treatment, and the surface will produce strong plastic deformation to obtain a uniform deformation structure and eliminate residual stress in a depth range.

Compared with the prior art, the present invention has the following beneficial effects:

The copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate and the preparation method thereof described in the present invention adopt a cold welding method to pre-deposit an aluminum bronze intermediate layer on the surface of the ductile iron, thereby avoiding the occurrence of white cast structure during the laser cladding process and improving the interface connection strength and fatigue resistance of the bimetallic plate; the aluminum bronze-graphite composite layer prepared by a method combining laser cladding and laser remelting technology has good thermal conductivity and low thermal expansion coefficient, and the prepared copper alloy-ductile iron bimetallic has good wear resistance and friction reduction performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a microstructure photograph of the copper alloy of the wear-resistant layer and the friction-reducing layer of the present invention.

FIG. 2 is a microstructure photograph of the copper alloy-ductile iron interface of the present invention.

FIG. 3 is a dry friction coefficient curve of the copper alloy of the wear-resistant layer and the friction-reducing layer of the present invention.

FIG. 4 is a shear strength curve of the copper alloy-ductile iron interface of the present invention.

DETAILED DESCRIPTION

The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The embodiments listed below are only for further understanding and implementation of the technical solution of the present invention, and do not constitute further limitations on the claims of the present invention. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

The copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate and the preparation method thereof described in the present invention include the following process steps:

In the first step, the surface of ductile iron is treated mechanically and chemically to remove oil, oxides and smooth the plate surface.

In the second step, a layer of aluminum bronze intermediate layer is deposited on the surface of the ductile iron by cold welding method. The cold welding process parameters are: power 50-80W, welding time 25-80s, intermediate layer alloy thickness 0.2-0.5mm, and the intermediate layer alloy forms a dense metallurgical bond with the ductile iron surface.

In the third step, the copper alloy powder is evenly spread on the middle layer of the surface of the ductile iron plate by the method of pre-setting powder to form a pre-set layer with a thickness of 0.8-1.2mm, and mechanical compaction is performed, and the pre-set copper alloy powder is subjected to multiple laser cladding. The copper alloy powder is heated by a fiber continuous laser to obtain a copper alloy cladding layer on the surface of the ductile iron. The high-energy-density fiber continuous laser described in the present invention is optimized to obtain the following process parameters for laser cladding: laser power 1600W, scanning speed 4mm/s, spot diameter 3.5mm, and defocus 30mm. The protective gas is argon, and the gas flow rate is 15L/min.

The fourth step is to mechanically mix the graphite reinforcement phase with the copper alloy powder, and use the pre-powder method to evenly spread the mixed powder on the copper alloy cladding layer on the surface of the ductile iron plate to form a pre-layer with a thickness of 0.8-1.2mm, and then mechanically compact it again, and repeat the third step of the laser cladding process. The mixing ratio of the graphite reinforcement phase and the copper alloy powder is 2.5-5 in terms of mass percentage (Wt/%) of the graphite reinforcement phase, and the rest is aluminum bronze powder. According to the designed component ratio, the graphite reinforcement phase and the copper alloy powder are evenly mixed and vacuum milled, with a ball milling speed of 150r/min and ball milling for 1h.

The fifth step is to mechanically grind the copper alloy cladding layer on the surface of the ductile iron to make it smooth.

In the sixth step, the copper alloy cladding layer on the surface of the ductile iron is subjected to mechanical vibration treatment, and finally a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate is formed. The mechanical vibration amplitude is 10 μm, the feed rate is 10 mm/min, and the vibration pressure is 300N.

The copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate and its preparation method described in the present invention can achieve the following technical indicators by preparing the plate according to the above process steps and components:

(1) The microhardness of the copper alloy wear-resistant and friction-reducing layer on the surface of ductile iron is 191.6-258.3HV;

(2) According to the YB/T 4286-2012 metal material thin plate and thin strip friction coefficient test method, GCr15 was selected as the grinding pair, and the dry friction coefficient of the wear-resistant and friction-reducing layer on the copper alloy surface was measured to be 0.028-0.059; compared with the case without graphite reinforcement, the relative wear resistance was 3.5-4.6;

(3) According to GB/T 6396-2008 composite steel plate mechanical and process performance test method, the shear strength of the copper alloy-ductile iron interface was measured to be 184-201Mpa;

The copper alloy-ductile iron bimetallic wear-resistant and friction-reducing plate and the preparation method thereof described in the present invention are obtained by adopting the above-mentioned components, process steps, processes and parameters in all the following embodiments.

The components and performance indicators of the wear-resistant and friction-reducing layer in the embodiment are shown in Table 1 below:

Table 1 Wear-resistant and friction-reducing layer copper alloy composition and performance indicators

Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily realized. Therefore, without departing from the general concept defined by the claims and equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims (1)

1. A preparation method of a copper alloy-nodular cast iron bimetal wear-resistant antifriction plate adopts a cold welding method to deposit an aluminum bronze intermediate layer on the surface of nodular cast iron, adopts a process combining laser cladding and laser remelting to prepare a graphite reinforced phase with wear-resistant antifriction performance on the surface of nodular cast iron, forms a wear-resistant antifriction layer with copper alloy, adopts a mechanical vibration process to carry out mechanical reinforcement treatment on a copper alloy cladding layer, and specifically comprises the following steps:

Firstly, mechanically and chemically treating the surface of spheroidal graphite cast iron, and removing greasy dirt, oxides and flat plate surfaces;

secondly, depositing an aluminum bronze intermediate layer on the surface of the spheroidal graphite cast iron by adopting a cold welding method, wherein the alloy of the intermediate layer and the surface of the spheroidal graphite cast iron form compact metallurgical bonding;

the cold welding process parameters are as follows: the power is 50-80W, the welding time is 25-80s, the thickness of the intermediate layer alloy is 0.2-0.5mm, and the intermediate layer alloy and the surface of the spheroidal graphite cast iron form compact metallurgical bonding;

thirdly, uniformly spreading copper alloy powder on the intermediate layer of the surface of the spheroidal graphite cast iron plate by adopting a preset powder method, carrying out mechanical compaction treatment, carrying out multi-channel laser cladding on the preset copper alloy powder, and obtaining a copper alloy cladding layer on the surface of the spheroidal graphite cast iron plate;

Fourthly, mechanically mixing the graphite strengthening phase with copper alloy powder, uniformly spreading the mixed powder on the copper alloy cladding layer on the surface of the spheroidal graphite cast iron plate by adopting a preset powder method, mechanically compacting again, repeating the laser cladding process of the third step, and obtaining the copper alloy cladding layer with wear resistance and antifriction on the surface of the spheroidal graphite cast iron while carrying out laser remelting on the copper alloy cladding layer of the third step;

The graphite is a high-purity component, is granular with the average diameter of 50-150 mu m, and is coated with a layer of metallic nickel on the surface; the mixing ratio of the graphite strengthening phase as the wear-resistant antifriction layer to the copper alloy powder is 2.5-5% of the graphite strengthening phase by mass percent Wt/% and the balance of the aluminum bronze powder;

fifthly, mechanically polishing and flattening the copper alloy cladding layer obtained on the surface of the spheroidal graphite cast iron;

and sixthly, carrying out mechanical vibration strengthening treatment on the copper alloy cladding layer obtained on the surface of the spheroidal graphite cast iron, and finally forming the copper alloy-spheroidal graphite cast iron bimetal wear-resistant antifriction plate.