CN115786850B

CN115786850B - Gradient coating material, preparation method and application thereof

Info

Publication number: CN115786850B
Application number: CN202211602055.0A
Authority: CN
Inventors: 王梦超; 陈辉; 刘艳; 王丽君; 胡登文; 张振林; 吴影
Original assignee: Southwest Jiaotong University
Current assignee: Southwest Jiaotong University
Priority date: 2022-12-13
Filing date: 2022-12-13
Publication date: 2024-01-19
Anticipated expiration: 2042-12-13
Also published as: CN115786850A

Abstract

The invention discloses a gradient coating material, a preparation method and application thereof, and relates to the technical field of coating materials. The gradient coating material comprises an adhesive layer, an intermediate transition layer and a top wear-resistant layer which are sequentially deposited on a hard alloy substrate, wherein the intermediate transition layer and the top wear-resistant layer both contain Ti, N and doping elements, the doping elements are silicon or silicon-aluminum mixture, other functional elements can be additionally added for achieving specific functions, and the content of the doping elements in the intermediate transition layer is gradually increased from bottom to top. Amorphous a-Si similar to honeycomb can be formed on the top layer ₃ N ₄ Composite structure of coating nano TiN crystal, which increases hardness of coating by fine crystal strengthening, but softer amorphous a-Si ₃ N ₄ The toughness of the coating can be improved by absorbing the energy of the crack and deflecting the crack direction to retard crack propagation. The preparation of the gradient coating with high wear resistance and strong combination can be realized, and the requirements of steel rail on-line milling processing can be met.

Description

Gradient coating material, preparation method and application thereof

Technical Field

The invention relates to the technical field of coating materials, in particular to a gradient coating material, a preparation method and application thereof.

Background

The steel rail is an important component of rail transit such as common iron, heavy load, subway, high-speed railway and the like, can provide a continuous and smooth rolling surface for wheels of carrying equipment, and is a foundation for guaranteeing the safe operation of the carrying equipment. The load of the carrying equipment is transmitted to the steel rail through the wheels, the steel rail bears huge pressure, and particularly, severe working conditions such as high load, strong impact, strong vibration and the like exist between the wheels and the rails under the high-speed and heavy-load running condition; the tread of the steel rail is repeatedly rolled for a long time continuously through wheels, so that fatigue cracks, peeling off blocks, crushing deformation, wave abrasion and other diseases are generated on the tread; in a curve, the strong extrusion of wheels and steel rails can cause side abrasion, fat edges and other diseases at the rail angle, so that the normal matching relationship of the wheels and the rails is changed, the problems of vibration, high noise and the like occur in the running process of high-speed carrying equipment, the abnormal abrasion of the wheels and the steel rails is accelerated, the running quality of a train and the service life of the steel rails are greatly reduced, and the running safety is even endangered.

In order to prevent and treat rail diseases, prolong the service life of the rail and improve the running quality of a train, and simultaneously solve the problems of high cost and long construction period caused by rail replacement, the rail needs to be repaired on line. At present, two modes are available for repairing damaged steel rails: one is rail grinding and the other is rail milling. The rail polishing depends on a rail polishing wagon, a plurality of grinding wheels are adopted to polish for multiple times and multiple passes, diseases on the shallow surface are removed, and the profile of the rail is repaired; the grinding wagon is only suitable for treating the steel rail with lighter disease, a large amount of dust is generated in the operation process, and the grinding wagon is not suitable for tunnel and underground construction. The milling of the steel rail depends on a steel rail milling vehicle, one or two groups of milling cutters (milling blades which are matched with each other) on a single side are adopted to carry out profile milling on the defective steel rail, and the defect of 0.3 mm-1.5 mm of the surface layer of the rail surface, 0.3 mm-3.0 mm of the rail side and the maximum 5mm of the rail gauge angle can be removed through one milling; the milling and grinding vehicle is suitable for eliminating serious diseases such as rail surface peeling, poor rail profile, rail wave grinding and the like, has high operation efficiency, no spark and dust, automatic dust collection of scrap iron, small influence on environment and wide application range, and is the development direction of future rail maintenance.

The milling blade is a key component of a steel rail milling and grinding vehicle and is a core for ensuring milling safety, precision and efficiency. The milling blade of the rail milling and grinding wagon takes hard alloy as a substrate, and a hard coating with the thickness of a few micrometers is deposited on the surface of the substrate so as to increase the wear resistance of the blade and prolong the service life of the blade. At present, a coating used for a steel rail milling and grinding lathe milling blade is mainly a TiAlN coating with uniform components and a single structure, the aluminum content is low aluminum (the atomic ratio is Ti: al=7:3) or medium aluminum (the atomic ratio is Ti: al=5:5), the coating is prepared on a blade substrate based on a Physical Vapor Deposition (PVD) technology, and the whole film layer is in a columnar crystal structure along the thickness direction. The steel rail milling faces severe working conditions such as dynamic movement, strong vibration and the like, the coating of the columnar crystal structure is easy to generate cracks under the impact load action in the milling process, the dynamic milling process promotes the crack to expand and connect into a net shape, the coating is caused to flake off in a blocking manner, and the blade is caused to fail prematurely; the steel rail materials widely used in railways in China are U71Mn and U75V, the structure of the steel rail materials contains more pearlite, and the dispersion degree of the steel rail materials is higher, so that the steel rail materials have higher hardness, toughness, plasticity and fatigue property, and under the milling working conditions of high speed, dry type and large feed amount of the milling cutter blade, the plastic deformation of the steel rail materials generates a large amount of heat, so that the surface temperature of the cutting edge of the cutter blade is increased, and the oxidation and abrasion of a coating are aggravated by the high temperature. In summary, the existing coating has insufficient toughness, poor oxidation resistance and poor wear resistance in the use process, and the main failure modes are network cracking and peeling, tipping and oxidative wear of the surface of the coating.

The coating used for the milling blade of the rail milling vehicle at present is TiAlN coating system, the oxidation resistance and the wear resistance of the coating are related to the content of Al in the coating, the AlTiN coating with high Al content has higher hardness, and a thin layer of Al is easy to generate on the surface at the high temperature generated by rail milling ₂ O ₃ ，Al ₂ O ₃ The coating has the functions of heat shielding and antifriction, can slow down the wear rate of the coating, protects the blade matrix, and has better performance than low-aluminum and medium-aluminum TiAlN coatings. However, the TiAlN coating with high Al content has large lattice distortion due to solid solution of Al element, can generate higher stress and reduces the film base binding force; on the other hand, because the coating has larger modulus difference with the hard alloy substrate (the elastic modulus of the TiAlN coating is reduced along with the increase of the Al content), the coating is inconsistent with the deformation of the substrate under the load effect, the interface of the film base is easy to crack,peeling off the coating and disabling the blade; furthermore, too high an Al content will cause the coating crystals to transform from Face Centered Cubic (FCC) to Hexagonal (HCP) structures, thereby deteriorating the performance of the coating, and therefore the highest Al content in the coating should be strictly controlled.

In order to adapt to the working conditions of strong vibration and high impact of steel rail on-line milling, it is important to improve the toughness of the hard coating and inhibit the formation and expansion of surface cracks. Most of coatings for milling blades are prepared by PVD (physical vapor deposition) technology, and the characteristic technical characteristics of PVD and the lamellar growth characteristic of films enable the section structure of the coatings prepared by the technology to mostly show the characteristics of columnar structures, and columnar grain boundaries are weak parts in the coatings and can become channels for cracks and rapid expansion of oxygen atoms. In order to improve the columnar structure of the coating, on one hand, one or more microelements (such as Al, V, si, Y, zr and the like) can be added into the traditional binary coating (such as TiN and CrN) to change the microstructure of the coating and strengthen the coating performance through solid solution strengthening, fine crystal strengthening or forming a second phase; on the other hand, the multi-layer structure (TiN/TiAlN) can be formed by alternately depositing two coatings (such as TiN and TiAlN) with different components, and the sensitivity of the coating to cracks can be improved by breaking the continuous growth of columnar crystals through the multi-interface structure. However, the former element doping distorts the coating lattice structure, worsens the stress state of the coating, and too much element doping can cause imbalance in the film base modulus matching; the latter multi-interface structure can still keep the continuous growth of columnar crystals of the coating due to the template effect when the modulation period is smaller, and interface stress accumulation and unstable interlayer combination can be caused by improper material matching between layers.

Therefore, aiming at the current situations of insufficient toughness, poor durability and low adaptability of the milling blade coating for online milling of the existing steel rail, how to provide a blade coating for online milling of the steel rail with high hardness, high toughness, high wear resistance and oxidation resistance under the condition of ensuring the binding force of a film base is a problem to be solved by the technicians in the field.

In view of this, the present invention has been made.

Disclosure of Invention

The invention aims to provide a gradient coating material, a preparation method and application thereof, and aims to prepare a gradient coating with high wear resistance and strong combination so as to meet the requirements of steel rail on-line milling processing.

The invention is realized in the following way:

in a first aspect, the present invention provides a gradient coating material, including an adhesion layer, an intermediate transition layer and a top wear layer sequentially deposited on a cemented carbide substrate, where each of the intermediate transition layer and the top wear layer contains Ti, N, and a doping element, where the doping element is silicon or a silicon-aluminum mixture, and where other functional elements Mo, V, Y, nb, ta, C, etc. may be added to achieve a specific function (e.g., mo, V, C elements may reduce the friction coefficient), where the content of the doping element in the intermediate transition layer increases gradually from bottom to top, and where the content of the doping element in the top wear layer is greater than or equal to the content of the doping element in the topmost intermediate transition layer.

In an alternative embodiment, the adhesive layer is selected from at least one of TiN, crN, zrN and VN; preferably a TiN coating;

preferably, the thickness of the bonding layer is 20 nm-200 nm, the thickness of the intermediate transition layer is 1-6 μm, and the thickness of the top wear-resistant layer is 1-3 μm;

preferably, the thickness of the bonding layer is 100 nm-200 nm, the thickness of the intermediate transition layer is 1.5-4 μm, and the thickness of the top wear-resistant layer is 1-2 μm;

preferably, in the deposition process of the intermediate transition layer, the content of doping elements in the coating is gradually increased, and the thickness of the single layer is regulated and controlled by the deposition time of each single layer, so that the thickness between layers is controlled to be 5-20 nm;

preferably, the cemented carbide substrate is a sub-microcrystalline cemented carbide with Co content of 8% -12% and WC grain size less than or equal to 0.6 μm.

In an alternative embodiment, the intermediate transition layer is a TiSiN coating with gradually increasing Si content, and the top wear-resistant layer is a TiSiN coating;

gradually reducing the atomic percentage of Ti from 45-60% to 30-50%, gradually increasing the atomic percentage of Si from 0-5% to 5-20% and keeping the atomic percentage of N at 40-50% from the bottom to the top of the intermediate transition layer;

in the top wear-resistant layer, the atomic percentage of Ti is 30% -50%, the atomic percentage of Si is 5% -20%, and the atomic percentage of N is 40% -50%.

In an alternative embodiment, the intermediate transition layer is a TiAlSiN coating with gradually increasing Si and Al contents, and the top wear-resistant layer is a TiAlSiN coating;

gradually reducing the atomic percentage of Ti from 46-60% to 20-30%, gradually increasing the atomic percentage of Al from 0-2% to 10-30%, gradually increasing the atomic percentage of Si from 0-2% to 3-10%, and keeping the atomic percentage of N at 40-50% from the bottom to the top of the intermediate transition layer;

in the top wear-resistant layer, the atomic percentage of Ti is 20% -30%, the atomic percentage of Al is 10% -30%, the atomic percentage of Si is 3% -10%, and the atomic percentage of N is 40% -50%.

In an alternative embodiment, a buffer layer is further provided between the bonding layer and the cemented carbide substrate;

preferably, the buffer layer is a Ti metal layer with the thickness of 10-100 nm; more preferably 10 to 20nm.

In a second aspect, the present invention provides a method for preparing a gradient coating material according to any one of the preceding embodiments, comprising: and sequentially depositing an adhesive layer, a middle transition layer and a top wear-resistant layer on the hard alloy substrate.

In an alternative embodiment, the method of preparation comprises:

depositing an adhesive layer: introducing nitrogen into the furnace chamber, starting a Ti target material, and depositing an adhesive layer on the hard alloy substrate;

Depositing an intermediate transition layer: continuously introducing nitrogen into the furnace chamber, simultaneously starting the Ti target and the Ti alloy target, keeping the current of the Ti target unchanged, and gradually increasing the current of the Ti alloy target; then keeping the current of the Ti alloy target unchanged, and gradually reducing the current of the Ti alloy target;

depositing a top wear layer: continuously introducing nitrogen into the furnace chamber, and starting a Ti alloy target material for deposition;

wherein the Ti alloy target is a TiSi alloy target or a TiAlSi alloy target, and the atomic mass ratio of Si in the TiSi alloy target is 20-25%; in the TiAlSi alloy target, the atomic mass ratio of Al is 35-45%, and the atomic mass ratio of Si is 5-15%;

preferably, before depositing the bonding layer, the hard alloy substrate is pretreated to remove surface oxide films and pollutants, then the hard alloy substrate is fixed in a furnace chamber, vacuumizing is carried out, the hard alloy substrate is heated to 400-500 ℃, then inert gas is introduced into the furnace chamber, the etched substrate is bombarded under the condition of negative bias, and the surface is cleaned.

In an alternative embodiment, the air pressure in the furnace is controlled to be 0.5X10 when depositing the adhesive layer ^-2 mbar～1.5×10 ^-2 Setting the current of the Ti target to be 110A-130A, and applying a negative bias voltage of 70V-90V;

Preferably, the gas pressure in the furnace is controlled to be 5.0X10 when the intermediate transition layer is deposited ^-2 mbar～7.0×10 ^-2 Applying a negative bias voltage of 50-70V to the mbar, simultaneously starting the Ti target and the Ti alloy target, wherein the current of the Ti target is kept between 110A and 130A, the current of the Ti alloy target is gradually increased from 80A to 100A, the step size is 1A to 3A, and the time interval for adjustment is 1min to 5min; when the current of the Ti alloy target is increased to be the same as the current of the Ti alloy target, keeping the current of the Ti alloy target unchanged, gradually reducing the current of the Ti alloy target, wherein the step length of the reduction is 1A-3A, the time interval of adjustment is 1 min-5 min until the current of the Ti alloy target is reduced to be consistent with the initial current of the Ti alloy target, and closing the Ti target;

preferably, the gas pressure in the furnace is controlled to be 5.0X10 when depositing the top wear layer ^-2 mbar～7.0×10 ^-2 And (3) applying a negative bias voltage of 40-60V to the mbar, setting the current of the Ti alloy target to be 110-130A, setting the deposition time to be 15-25 min, closing the Ti alloy target, stopping introducing nitrogen and closing the negative bias voltage.

In an alternative embodiment, a Ti metal buffer layer is deposited prior to depositing the adhesion layer;

preferably, when depositing the Ti metal buffer layer, inert gas is introduced into the furnace chamber, and the gas pressure is kept to be 0.5X10 ^- ² mbar～1.5×10 ^-2 The mbar opens the Ti target, the Ti target current is set to be 110A-130A, and a negative bias voltage of 70V-90V is applied to the workpiece frame.

In a third aspect, the present invention provides the use of a gradient coating material according to any one of the preceding embodiments or a gradient coating material prepared by a method according to any one of the preceding embodiments in the preparation of a blade.

The invention has the following beneficial effects: by sequentially depositing the bonding layer, the intermediate transition layer and the top wear-resistant layer on the hard alloy substrate, the intermediate transition layer and the top wear-resistant layer both contain Ti, N and doping elements, the doping element content in the intermediate transition layer is controlled to be gradually increased from bottom to top by optimizing the doping element types, and the doping element content in the top wear-resistant layer is enabled to be in a higher level. The technical proposal of the invention can form amorphous a-Si similar to honeycomb shape on the top layer ₃ N ₄ Composite structure of coating nano TiN crystal, which increases hardness of coating by fine crystal strengthening, but softer amorphous a-Si ₃ N ₄ The toughness of the coating can be improved by absorbing the energy of the crack and deflecting the crack direction to retard crack propagation. Based on the design principle, the preparation of the gradient coating with high wear resistance and strong combination can be realized, and the requirements of steel rail on-line milling processing can be met.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a microstructure of mussels;

FIG. 2 is a schematic diagram of a gradient coating structure;

FIG. 3 illustrates the bonding layer forming a coherent interface with the substrate WC;

FIG. 4 is a schematic diagram of a gradient coating preparation apparatus;

FIG. 5 is a scanning electron microscope test chart of a cross section of the coating material prepared in example 1;

FIG. 6 is a transmission electron microscope test chart of a cross section of the coating material prepared in example 1;

FIG. 7 is a response to nanoindentation of a single structure coating with the gradient structure coating of example 1;

FIG. 8 is a scanning electron microscope test chart of a cross section of the coating material prepared in example 1 after 1h oxidation at 850 ℃;

FIG. 9 is a scanning electron microscope test chart of a cross section of the coating material prepared in example 2;

FIG. 10 is a nanoindentation hardness plot of a gradient TiAlSiN coating tested using the continuous stiffness method;

FIG. 11 shows that the TiAlSiN gradient coating is free of flaking under 60Kg load indentations;

FIG. 12 is a scanning electron microscope test chart of a cross section of the coating material prepared in example 2 after 1h oxidation at 850 ℃;

FIG. 13 is a scanning electron microscope test chart of a cross section of the coating material prepared in comparative example 1;

FIG. 14 is a nanoindentation hardness plot of a gradient AlTiN coating tested using the continuous stiffness method;

FIG. 15 is a scanning electron microscope test chart of a cross section of the coating material prepared in comparative example 1 after 1h oxidation at 850 ℃;

FIG. 16 is a scanning electron microscope test chart of a cross section of the coating material prepared in comparative example 2;

FIG. 17 is a transmission electron microscope test chart of a cross section of the coating material prepared in comparative example 2.

Icon: 1-loading a target material; 2-lower target material; 3-loading the target axis; 4-lower target axis; 5-feeding a target power supply; 6-a lower target power supply; 7-a gas flow guide pipe; 8-a triaxial rotating workpiece holder; 9-a work rest bias power supply; 10-revolution schematic direction of the work holder (first axis); 11-revolution schematic direction of the work holder (second axis); 12-the workpiece holder rotates in the direction of illustration (third axis); 13-a target particle stream; 14-a substrate or a workpiece; 15-a mixed plasma region; 16-a heater; 17-furnace chamber; 18-vacuum system.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

In nature, mussels have higher hardness and toughness, and have better protectiveness and higher impact resistance on the internal soft structure. Analyzing the structure of the mussel, the mussel is a composite gradient material (shown in figure 1), the outermost layer is a horny layer composed of sclerotin, the middle layer is a prismatic layer, the innermost layer is a pearl layer, and the tissue structure of the mussel is gradually changed from inside to outside. The inventor creatively refers to the bionic structure construction components of mussels and the coating structure with gradient change of crystal structure, so as to achieve the purposes of slowly releasing the stress of the coating, improving the binding force of a film base, increasing the toughness of the coating and improving the high-temperature oxidation resistance.

As shown in fig. 2, an embodiment of the present invention provides a gradient coating material having a multi-layered structure, which can be divided into three different functional layers including an adhesive layer, a middle transition layer and a top wear layer sequentially deposited on a cemented carbide substrate. The intermediate transition layer and the top wear-resistant layer both contain Ti, N and doped elements, the doped elements are silicon or silicon-aluminum mixtures, other functional elements Mo, V, Y, nb, ta, C and the like (for example, mo, V and C elements can reduce friction coefficient) can be additionally added for achieving specific functions, the content of the doped elements in the intermediate transition layer is gradually increased from bottom to top, and the content of the doped elements in the top wear-resistant layer is greater than or equal to the content of the doped elements in the topmost intermediate transition layer.

It should be noted that, the content of doping element (Si or al—si) is continuously increased in a layer-by-layer gradient in the intermediate transition layer, so that lattice distortion caused by element doping in the coating is gradually changed, and the stress of the coating accumulated due to high doping amount in the single-layer structure can be relieved. As a result of the gradient change of the components, the elastic modulus and the hardness of the coating material are also changed in a gradient way, and the interface between layers has higher phase by the coordinated deformation and the gradient change of the componentsThe compatibility can reduce the cracking risk of an interlayer interface. The top layer structure of the high doping element can provide better performance for the coating, the TiSiN top layer with high Si content provides higher hardness and high-temperature oxidation resistance, when the doping amount of the Si element reaches a certain degree, the existence form of the Si element can be converted from a solid solution state to form a second phase, and particularly, amorphous a-Si with a thickness of several atomic layers is formed ₃ N ₄ Forming the top layer into amorphous a-Si similar to honeycomb ₃ N ₄ Composite structure of coating nano TiN crystal, which increases hardness of coating by fine crystal strengthening, but softer amorphous a-Si ₃ N ₄ The toughness of the coating can be improved by absorbing the energy of the crack and deflecting the crack direction to retard crack propagation.

Specifically, the kind of the cemented carbide substrate is not limited, and may be a conventional cemented carbide. In some embodiments, the hard alloy substrate is a sub-microcrystalline hard alloy with Co content of 8% -12% and WC grain size less than or equal to 0.6 μm, and has high strength, toughness and impact resistance. In some embodiments, the cemented carbide substrate may be a cemented carbide insert blank having the same shape as a rail mill train insert, and a gradient coated insert may be prepared for use with a rail mill train.

Specifically, the adhesive layer is selected from at least one of TiN, crN, zrN and VN; tiN coatings are preferred. The TiN coating has higher elastic modulus, can be matched with a hard alloy substrate with high elastic modulus, can keep the complete structure of the film base interface through cooperative deformation under the action of load, and reduces the cracking trend of the film base interface; in addition, tiN crystals can form coherent interfaces (as shown in fig. 3) at specific orientations of WC grains of the cemented carbide substrate, improving the strength and toughness of the interfaces.

In the deposition process of the intermediate transition layer, the content of doping elements in the coating is gradually increased, the thickness of a single layer is regulated and controlled according to the deposition time of each single layer, the thickness between layers is controlled to be 5-20 nm, and the doping elements are gradually increased layer by layer to form a product with gradient change of the doping elements. According to the doping elements, the intermediate transition layer and the top wear-resistant layer have the following two realization forms:

in some embodiments, the intermediate transition layer is a TiSiN coating with a progressively increasing Si content and the top wear layer is a TiSiN coating. To further ensure the performance of the gradient coating material, the inventors have optimized the content of atoms in the intermediate transition layer to the top wear layer: gradually reducing the atomic percentage of Ti from 45-60% to 30-50%, gradually increasing the atomic percentage of Si from 0-5% to 5-20% and keeping the atomic percentage of N at 40-50% from the bottom to the top of the intermediate transition layer; in the top wear-resistant layer, the atomic percentage of Ti is 30% -50%, the atomic percentage of Si is 5% -20%, and the atomic percentage of N is 40% -50%.

In another embodiment, the intermediate transition layer is a TiAlSiN coating with increasing Si and Al content, and the top wear layer is a TiAlSiN coating. To further ensure the performance of the gradient coating material, the inventors have optimized the content of atoms in the intermediate transition layer to the top wear layer: gradually reducing the atomic percentage of Ti from 46-60% to 20-30%, gradually increasing the atomic percentage of Al from 0-2% to 10-30%, gradually increasing the atomic percentage of Si from 0-2% to 3-10%, and keeping the atomic percentage of N at 40-50% from the bottom to the top of the intermediate transition layer; in the top wear-resistant layer, the atomic percentage of Ti is 20% -30%, the atomic percentage of Al is 10% -30%, the atomic percentage of Si is 3% -10%, and the atomic percentage of N is 40% -50%.

It should be noted that, for convenience of control, the composition of the elements in the top wear layer may be the same as the composition of the elements at the top of the intermediate transition layer.

The inventors optimize the thickness of each layer to further improve the overall performance of the material: the thickness of the bonding layer is 20 nm-200 nm, the thickness of the intermediate transition layer is 1-6 mu m, and the thickness of the top wear-resistant layer is 1-3 mu m; preferably, the thickness of the adhesive layer is 100nm to 200nm, the thickness of the intermediate transition layer is 1.5 μm to 4 μm, and the thickness of the top wear-resistant layer is 1 μm to 2 μm.

It should be noted that the adhesive layer, the intermediate transition layer and the top wear-resistant layer can be designed according to the needs, and the intermediate layer is deposited after the deposition of the adhesive layer is finished, at this time, the content of doping elements in the coating is gradually increased (in practical operation, by changing the current of the corresponding target material), a layered structure with gradually changed components is formed in microcosmic, the interface between the layers is difficult to distinguish in morphology observation, and the compatibility between the layers is good. On top of the intermediate transition layer, the content of doping elements (Si content) in the coating reaches the designed highest value. The top wear-resistant layer is the layer with the highest doping element content, has better mechanical and tribological properties, and due to the design of the bonding layer and the transition layer, the accumulated stress is effectively relaxed, and the film base binding force of the coating is ensured.

Specifically, the thickness of the adhesive layer may be 20nm, 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, or any value between the above adjacent values; the thickness of the intermediate transition layer may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, etc., or may be any value between the above adjacent values; the thickness of the top wear layer may be 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, etc., or any value between the above adjacent values.

In some embodiments, a buffer layer is also provided between the bond layer and the cemented carbide substrate, by which the coating stress may be further relieved. The buffer layer can be a Ti metal layer with a thickness of 10-100 nm (such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc.); more preferably 10 to 20nm.

The embodiment of the invention also provides a preparation method of the gradient coating material, which adopts a multi-arc ion plating technology to sequentially deposit an adhesive layer, a middle transition layer and a top wear-resistant layer on a hard alloy substrate, and can also deposit a buffer layer before depositing the adhesive layer, and specifically comprises the following steps:

s1, pretreatment of a substrate

The surface oxide film and pollutants can be removed by pretreatment, the surface is etched, the surface is roughened on microcosmic scale, and the specific surface area of the substrate is increased.

Specifically, the method for removing the surface oxide film and the contaminant is not limited, and the following steps may be adopted: grinding, polishing or wet blasting and ultrasonic cleaning are carried out on the hard alloy substrate or the blade with the corresponding combined structure so as to remove oxide films and pollutants on the surface, and drying is carried out for later use.

In some embodiments, the step of etching the surface of the substrate comprises: fixing the hard alloy substrate on a workpiece frame in a furnace chamber, and closing a furnace door of the coating equipment; starting the mechanical pump and molecular pump step by step to vacuum the furnace chamber to 3.0X10 ^- ⁵ mba～5.0×10 ^-5 mba (e.g. 4.0X10) ^-5 mbar) background vacuum below; turning on the heater to heat the substrate to about 400-500 deg.c (e.g., 450 deg.c); ar gas is introduced into the furnace chamber, and the air pressure is kept to be 0.5 multiplied by 10 ^-2 mbar～1.5×10 ^-2 mbar (e.g. 1.0X10) ^-2 mbar) of 280-320V (e.g. 300V) by Ar ⁺ The substrate is bombarded and etched for 20-40min (30 min, for example), the surface is further cleaned, the surface is roughened on microcosmic scale, and the specific surface area of the substrate is increased.

S2, depositing a buffer layer

To further improve the stress state of the coating, a Ti metal buffer layer is deposited prior to depositing the adhesion layer.

In the actual operation process, inert gas (such as argon) is introduced into the furnace chamber during the deposition of the Ti metal buffer layer, and the air pressure is kept to be 0.5X10 ^-2 mbar～1.5×10 ^-2 mbar (e.g. 1.0X10) ^-2 mbar), turning on the Ti target, setting the current of the Ti target to be 110-130A (such as 120A), applying a negative bias voltage of 70-90V (such as 80V) on the workpiece frame, and ensuring the deposition thickness of the buffer layer to be described in other parts of the specification.

S3, depositing an adhesive layer

And (3) introducing nitrogen into the furnace chamber, starting the Ti target, and depositing an adhesive layer on the hard alloy substrate, wherein the thickness of the adhesive layer can be described in other parts of the specification.

In the actual operation process, when the adhesive layer is deposited, N is introduced into the furnace chamber ₂ Controlling the air pressure in the furnace to be 0.5 multiplied by 10 ^-2 mbar～1.5×10 ^-2 mbar (e.g. 1.0X10) ^-2 mbar), the current of the Ti target is set to be 110-130A (120V, for example), and a negative bias voltage of 70-90V (80V, for example) is applied.

S4, depositing an intermediate transition layer

Continuously introducing nitrogen into the furnace chamber, simultaneously starting the Ti target and the Ti alloy target, keeping the current of the Ti target unchanged, and gradually increasing the current of the Ti alloy target; and then keeping the current of the Ti alloy target unchanged, and gradually reducing the current of the Ti alloy target. The gradient change of doping elements is realized by controlling the currents of the Ti alloy target and the Ti target.

Specifically, the Ti alloy target is TiSi alloy target or TiAlSi alloy target, and the atomic mass ratio of Si in the TiSi alloy target is 20-25%; in the TiAlSi alloy target, the atomic mass ratio of Al is 35-45%, and the atomic mass ratio of Si is 5-15%. And selecting a proper target material according to the composition of the prepared intermediate transition layer to prepare, wherein the target material can be a TiSi alloy target material or a TiAlSi alloy target material.

In the actual operation process, when the intermediate transition layer is deposited, N is continuously introduced into the furnace chamber ₂ Controlling the air pressure in the furnace to be 5.0 multiplied by 10 ^-2 mbar～7.0×10 ^-2 mbar (e.g. 6.0X10) ^-2 mbar), applying a negative bias voltage of 50-70V (such as 60V), simultaneously starting a Ti target and a Ti alloy target, wherein the current of the Ti target is kept between 110A and 130A (such as 120A), the current of the Ti alloy target is gradually increased from 80A to 100A (such as 90A), the increasing step length is 1A to 3A, and the adjusting time interval is 1min to 5min; when the current of the Ti alloy target is increased to be the same as the current of the Ti alloy target, keeping the current of the Ti alloy target unchanged, gradually reducing the current of the Ti alloy target, wherein the step length of the reduction is 1A-3A, the time interval of adjustment is 1 min-5 min until the current of the Ti alloy target is reduced to be consistent with the initial current of the Ti alloy target, and closing the Ti target. Specifically, in the deposition process of the intermediate transition layer, the thickness of the single layer is regulated and controlled according to the deposition time of each single layer, the thickness between layers is controlled to be 5-20 nm, and the doping element content is increased layer by layer to form a product with gradient change of the doping element.

It should be noted that, keeping the current of the Ti target constant gradually increases the current of the Ti alloy target, so as to increase the concentration of particles (such as Si and Al) generated by the Ti alloy target in the mixed plasma region, and gradually increase the Si content in the coating; the Ti alloy target current is kept unchanged, the Ti target current is gradually reduced, the concentration of Ti particles generated by the Ti target in the mixed plasma region can be reduced, the content of doping elements in the coating is gradually increased, and the gradient change of the content of the doping elements is realized.

S5, depositing a top wear-resistant layer

And continuously introducing nitrogen into the furnace chamber, and starting the Ti alloy target for deposition, wherein the Ti alloy target can be the same as S4.

In the actual operation process, continuously introducing N into the furnace chamber ₂ Controlling the air pressure in the furnace to be 5.0 multiplied by 10 ^-2 mbar～7.0×10 ^-2 mbar (e.g. 6.0X10) ^-2 mbar), applying a negative bias voltage of 40-60V (such as 50V), setting the current of the Ti alloy target material to be 110-130A (such as 120A), depositing for 15-25 min (such as 20 min), closing the Ti alloy target material, stopping introducing nitrogen, and closing the negative bias voltage.

It is added that after the deposition is completed, after the furnace chamber is cooled to below 100 ℃, N is filled into the furnace chamber ₂ And opening the furnace door to one atmosphere, and taking out the substrate sample to obtain the product of the gradient coating material.

The gradient coating material provided by the embodiment of the invention can be expanded and applied to processing blades of other key parts in the field of high-speed trains, such as processing blades of wheels, axles, bogies and the like.

To better achieve gradient coating preparation, embodiments of the present invention also provide an apparatus for preparing gradient coatings, as shown in FIG. 4. The device comprises a furnace chamber 17, an upper target 1, a lower target 2, an upper target power supply 5, a lower target power supply 6, a gas flow guide pipe 7, a triaxial rotating workpiece frame 8, a workpiece frame bias power supply 9, a heater 16 and a vacuum system 18.

Specifically, the upper target 1 and the lower target 2 are obliquely installed in the furnace chamber 17, the upper target 1 and the lower target 2 are respectively powered by the upper target power supply 5 and the lower target power supply 6, the furnace chamber 17 is ventilated (such as nitrogen) through the gas guide pipe 7, the furnace chamber 17 is heated by the heater 16, and the furnace chamber 17 is vacuumized by the vacuum system 18. When the device works, a substrate or a workpiece 14 is arranged on a triaxial rotating workpiece frame 8, a workpiece frame bias power supply 9 is used for providing bias, the triaxial rotating workpiece frame 8 has a triaxial rotating mode, namely a workpiece frame revolution schematic direction (a first shaft) 10, a workpiece frame revolution schematic direction (a second shaft) 11 and a workpiece frame rotation schematic direction (a third shaft) 12, and the selection and installation of the workpiece frame can also generate a physical stirring effect on a mixed plasma region of a target material; the target particle stream 13 generated by the upper target 1 and the lower target 2 is deposited on a substrate or workpiece.

The upper target 1 and the lower target 2 are two targets distributed on the furnace chamber wall in different height directions, and in order to better realize the preparation of the gradient coating, the installation height of the hard alloy substrate should be at the middle height of the two targets, so that the substrate can be positioned in a mixed plasma region 15 formed by two target particles. In order to make the mixed plasma region 15 of the two targets more uniform, the two targets should be arranged obliquely so that the axes of the two targets (i.e., the upper target axis 3 and the lower target axis 4) intersect within the radius of gyration of the base turntable.

In some embodiments, multiple rows of targets may be provided around the circumference of the chamber wall of the device for enriching its functionality and increasing the deposition rate of the coating, which may be independently or cooperatively controlled during the coating process.

In addition, the gradient coating can be directly realized on the traditional equipment or after the traditional equipment is slightly modified, and the popularization and application cost is low.

The features and capabilities of the present invention are described in further detail below in connection with the examples.

Example 1

The embodiment provides a preparation method of a gradient coating material, which comprises a TiN bonding layer, a TiSiN intermediate transition layer and a TiSiN top wear-resistant layer, wherein the Si content of the TiSiN intermediate transition layer is gradually increased along the thickness direction of the coating. The preparation process comprises the following steps:

(1) Pretreatment of substrates

Grinding, polishing or wet blasting hard alloy substrate with Co content of 12%, WC content of 87%, taC content of 1% and average sectional grain size of 500nm, and ultrasonic cleaning to remove surface oxidationMembrane and contaminant, dry for use; fixing the hard alloy on a workpiece frame, and closing a furnace door of the coating equipment; starting the mechanical pump and molecular pump step by step to vacuumize the furnace chamber to 4.0X10 ^-5 Background vacuum below mbar; turning on the heater to heat the substrate to about 450 ℃; ar gas is introduced into the furnace chamber, and the air pressure is kept to be 1.0x10 ^-2 mbar, applying a negative bias of 300V to the work holder, through Ar ⁺ And bombarding and etching the substrate for 30min.

(2) Depositing an adhesive layer

Introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 1.0X10 ^-2 Starting a Ti target material, setting the current of the Ti target material to be 120A, applying a negative bias voltage of 80V on a workpiece frame, depositing a TiN bonding layer, wherein the thickness of the bonding layer is 150nm, and the atomic ratio of Ti atoms to N atoms is close to 1:1, and the crystal structure is a single-phase FCC structure.

(3) Depositing an intermediate transition layer

Continuously introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 6.0X10 ^-2 And applying a 60V negative bias voltage on the workpiece frame, simultaneously starting a Ti target and a TiSi alloy target (the atomic ratio of the TiSi alloy target is Ti: si=75:25), keeping the current of the Ti target at 120A, setting the current of the TiSi alloy target at 90A and gradually increasing, increasing the step length to 2A, and adjusting the time interval to 3min. When the current of the TiSi alloy target is increased to 120A, keeping the current of the TiSi alloy target unchanged, starting to gradually reduce the current of the Ti target, wherein the step length of the reduction is 2A, the time interval of adjustment is 3min until the current of the Ti target is reduced to 90A, and closing the Ti target.

The Si content of the TiSiN intermediate transition layer gradually increases along the thickness direction of the coating, and the thickness of the TiSiN intermediate transition layer is 3 mu m.

(4) Depositing a top wear layer

Continuously introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 6.0X10 ^-2 Applying a negative bias voltage of 50V on the workpiece frame, keeping the current of the TiSi alloy target material to be 120A, depositing for 20min (the thickness of the top wear-resistant layer is 1 mu m), closing the TiSi alloy target material, and stopping introducing N into the furnace chamber ₂ And closing the negative bias power supply on the workpiece rest. Raw Si in top wear layerThe sub-percentage is 10%, the atomic percentage of Ti is 44%, and the atomic percentage of N is 46%.

After the furnace chamber is cooled to below 100 ℃, N is filled into the furnace chamber ₂ To one atmosphere, the oven door was opened and the substrate sample was removed.

Referring to fig. 5, in this embodiment, the Si content gradient is increased by the cooperation of the Ti target and the TiSi alloy target current gradually changed during the deposition of the intermediate transition layer, the atomic percentage of Ti in the coating gradually decreases from 50% to 40% along the thickness direction of the coating, the atomic percentage of Si gradually increases from 0% to 10%, and the atomic percentage of N remains 40% -50%; when the content of Si atoms is low (about 7 percent, depending on a deposition process), the Si atoms exist in a TiN crystal in a solid solution form, the mechanical property is improved through a refined crystal grain and a solid solution strengthening form, and the coating structure still maintains the FCC structure of the TiN at the stage; as the Si content continues to rise, the Si element will form Si of several atomic layer thicknesses around the TiN grains ₃ N ₄ Amorphous phase, forming amorphous a-Si ₃ N ₄ The amorphous phase can break the growth of columnar crystal grains and refine the crystal grains, and changes the structure of long columnar crystal into a nano composite structure, which is used as a channel for absorbing crack energy, and the crack is prevented from generating and expanding by closing and deflecting the crack (see figure 6).

As shown in FIG. 7, the hardness of the coating can reach more than 37GPa by adopting a nano indentation test, in addition, the film base binding force of the coating is more than or equal to 93N by adopting a scratch method, and the residual stress of the coating is measured on the basis of a substrate curvature method, wherein the residual stress of the coating with a single structure is-4.03+/-0.03 GPa, the residual stress of the coating with a gradient structure is-2.7+/-0.02 GPa, and the residual stress is reduced by about 33%; under the nanoindentation load of 200mN, the gradient coating surface has better crack inhibition capability; oxidation of Si element on the surface layer at high temperature to form dense SiO ₂ Can prevent O atoms from diffusing into the coating to a certain extent, improve the oxidation resistance of the coating, and in addition, siO ₂ The lubricating and antifriction effects can be achieved; after oxidation in an air atmosphere at 850 ℃ for 1h, the thickness of the oxide layer was only 140nm (see fig. 8).

Note that: the single coating in fig. 7 refers to a uniformly composed TiSiN coating in which the atomic percent of Ti is 44%, the atomic percent of N is 48%, and the atomic percent of Si is 8%.

Example 2

The embodiment provides a preparation method of a gradient coating material, which comprises a TiN bonding layer, a TiAlSiN intermediate transition layer and a TiAlSiN top wear-resistant layer, wherein the TiAlSiN intermediate transition layer gradually increases Si and Al contents along the thickness direction of the coating. The preparation process comprises the following steps:

(1) Pretreatment of substrates

Grinding, polishing or wet blasting and ultrasonic cleaning a hard alloy flat plate substrate with the Co content of 10%, the WC content of 88.5% and the TaC content of 1.5% and the average sectional grain size of 600nm to remove oxide films and pollutants on the surface, and drying for later use; fixing the hard alloy on a workpiece frame, and closing a furnace door of the coating equipment; starting the mechanical pump and molecular pump step by step to vacuumize the furnace chamber to 4.0X10 ^-5 Background vacuum below mbar; turning on the heater to heat the substrate to about 450 ℃; ar gas is introduced into the furnace chamber, and the air pressure is kept to be 1.0x10 ^-2 mbar, applying a negative bias of 300V to the work holder, through Ar ⁺ And bombarding and etching the substrate for 30min.

(2) Depositing a buffer layer

Ar gas is continuously introduced into the furnace chamber, and the air pressure is kept to be 1.0 multiplied by 10 ^-2 And (3) mbar, starting a Ti target, setting the current of the Ti target to 120A, applying a negative bias voltage of 80V on a workpiece frame, and depositing a Ti metal buffer layer with the thickness of 50nm.

(3) Depositing an adhesive layer

Introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 1.0X10 ^-2 Starting a Ti target material, setting the current of the Ti target material to be 120A, applying a negative bias voltage of 80V on a workpiece frame, depositing a TiN bonding layer, wherein the thickness of the bonding layer is 200nm, and the atomic ratio of Ti atoms to N atoms is close to 1:1, and the crystal structure is a single-phase FCC structure.

(4) Depositing an intermediate transition layer

Continuously introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 6.0X10 ^-2 And applying a 60V negative bias voltage on the workpiece frame, simultaneously starting a Ti target and a TiAlSi alloy target (the atomic ratio of the TiAlSi alloy target is Ti: al: si=50:40:10), keeping the current of the Ti target at 120A, setting the current of the TiAlSi alloy target to 90A and gradually increasing, setting the increasing step length to 1A, and adjusting the time interval to 2min. When the current of the TiAlSi alloy target is increased to 120A, keeping the current of the TiAlSi alloy target unchanged, starting to gradually reduce the current of the Ti target, wherein the step length of the reduction is 1A, the time interval of adjustment is 2min until the current of the Ti target is reduced to 90A, and closing the Ti target.

The TiAlSiN intermediate transition layer gradually increases Si and Al contents along the thickness direction of the coating, and the thickness thereof is 2.5 μm.

(5) Depositing a top wear layer

Continuously introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 6.0X10 ^-2 Applying a negative bias voltage of 50V on the workpiece frame, keeping the current of the TiAlSi alloy target material to be 120A, depositing for 20min, closing the TiAlSi alloy target material, and stopping introducing N into the furnace chamber ₂ And closing the negative bias power supply on the workpiece rest. The top wear-resistant layer adopts an independent TiAlSi alloy target material (the atomic ratio is Ti: al: si=50:40:10), and a TiAlSiN wear-resistant layer with high Al and Si content doped elements is deposited, wherein the thickness is 1 mu m, the atomic percentage of Ti is 26%, the atomic percentage of Al is 20%, the atomic percentage of Si is 4%, and the atomic percentage of N is 50%.

Referring to fig. 9, in this embodiment, the atomic percentage of Ti in the deposited intermediate transition layer coating gradually decreases from 50% to 25%, the atomic percentage of Al gradually increases from 0% to 20%, the atomic percentage of Si gradually increases from 0% to 4%, and the atomic percentage of N remains 40% -50%; the simultaneous doping of Al and Si atoms can reduce the solid solubility of TiN in the FCC structure, so that the micro doping of the Al and Si atoms can change the microstructure of the coating, so that the columnar structure of the coating is gradually transited to the glassy morphology without obvious characteristics, grains are thinned, and the hardness of the coating is improved.

Referring to fig. 10 and 11, the hardness of the coating can reach more than 39GPa when the nano indentation test is adopted, and the film base binding force of the coating is more than or equal to 90N; the coating did not flake off under 60Kg load of indentation. The top wear-resistant layer forms compact Al under the synergistic effect of Al and Si elements on the surface layer at high temperature ₂ O ₃ And SiO ₂ The layer can further improve the high-temperature oxidation resistance and red hardness of the coating; after oxidation for 1h in an air environment at 850 ℃, the thickness of the oxide layer is only 120nm (see figure 12), and the high-temperature oxidation resistance of the coating is effectively improved.

Comparative example 1

The comparative example provides a preparation method of a gradient coating material, which comprises a TiN bonding layer, an AlTiN intermediate transition layer and an AlTiN top wear-resistant layer, wherein the Al content of the AlTiN intermediate transition layer is gradually increased along the thickness direction of the coating. The preparation process comprises the following steps:

(1) Pretreatment of substrates

The procedure was the same as in example 1.

(2) Depositing an adhesive layer

(3) Depositing an intermediate transition layer

Continuously introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 6.0X10 ^-2 And applying a 60V negative bias voltage on the workpiece frame, simultaneously starting a Ti target and a TiAl alloy target (the atomic ratio of the TiAl alloy target is Ti: al=33:67), keeping the current of the Ti target at 120A, setting the current of the TiAl alloy target at 90A and gradually increasing, increasing the step length to 2A, and adjusting the time interval to 3min. When the current of the TiAl alloy target is increased to 120A, keeping the current of the TiAl alloy target unchanged, starting to gradually reduce the current of the Ti target, wherein the step length of the reduction is 2A, the time interval of adjustment is 3min until the current of the Ti target is reduced to 90A, and closing the Ti target.

The Al content of the TiAlN intermediate layer gradually increases along the thickness direction of the coating, and the thickness of the TiAlN intermediate layer is 3 mu m.

(4) Depositing a top wear layer

Continuously introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 6.0X10 ^-2 Applying a negative bias voltage of 50V on the workpiece frame, keeping the current of the TiAl alloy target material to be 120A, depositing for 20min (the thickness of the top wear-resistant layer is 1 mu m), closing the TiAl alloy target material, and stopping introducing N into the furnace chamber ₂ And closing the negative bias power supply on the workpiece rest. The top wear-resistant layer adopts TiAl alloy target material (the atomic ratio is Ti: al=33:67), and is deposited with high aluminum content AlTiN wear-resistant layer with the thickness of 2 mu m, wherein the atomic percentage of Al is 32%, the atomic percentage of Ti is 21%, and the atomic percentage of N is 47%.

Referring to fig. 13, in the present comparative example, the Al content was increased in gradient with the cooperation of the gradually changing TiAl target current and Ti target, the atomic percentage of Ti in the coating was gradually decreased from 50% to 15% along the thickness direction of the coating, the atomic percentage of Al was gradually increased from 0% to 35%, and the atomic percentage of N was maintained at 40% to 50%; due to the coating process and the precise control of the Al content components, the crystal structure of the coating still remains as a single-phase FCC structure along with the increase of the Al content, and the coating phase structure is a solid solution of Al in TiN crystals, and a hexagonal phase structure with deteriorated performance does not appear.

Referring to fig. 14, the hardness of the coating can reach 31GPa by nano-indentation test, the film-based bonding force of the coating is about 80N, although the Al gradient coating prepared by the method of the present invention also has good hardness and bonding force, but does not form an amorphous phase of a second phase, and the coating is oxidized completely in an air environment at 850 ℃ for 1h (see fig. 15), which is not suitable for high temperature application.

Comparative example 2

The only difference from example 2 is that: the comparative example incorporates excessive amounts of doping elements Al and Si, resulting in excessive generation of amorphous phase in the coating, making the crystallinity of the coating poor and the coating softened. The preparation process comprises the following steps:

(1) Pretreatment of substrates

The procedure was the same as in example 2.

(2) Depositing a buffer layer

The procedure is the same as in example 2

(3) Depositing an adhesive layer

(4) Depositing an intermediate transition layer

Continuously introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 6.0X10 ^-2 And applying a 60V negative bias voltage on the workpiece frame, simultaneously starting a Ti target and a TiAlSi alloy target (the atomic ratio of the TiAlSi alloy target is Ti: al: si=30:60:10), keeping the current of the Ti target at 120A, setting the current of the TiAlSi alloy target to 90A and gradually increasing, setting the increasing step length to 1A, and adjusting the time interval to 2min. When the current of the TiAl alloy target is increased to 120A, keeping the current of the TiAl alloy target unchanged, starting to gradually reduce the current of the Ti target, wherein the step length of the reduction is 1A, the time interval of adjustment is 2min until the current of the Ti target is reduced to 90A, and closing the Ti target.

(5) Depositing a top wear layer

Continuously introducing N into the furnace chamber ₂ Gas, maintaining the gas pressure at 6.0X10 ^-2 Applying a negative bias voltage of 50V on the workpiece frame, keeping the current of the TiAlSi alloy target material to be 120A, depositing for 20min (the thickness of the top wear-resistant layer is 1 mu m), closing the TiAlSi alloy target material, and stopping introducing N into the furnace chamber ₂ And closing the negative bias power supply on the workpiece rest. The top wear-resistant layer adopts TiAlSi alloy target material (the atomic ratio is Ti: al: si=30:60:10), and the TiAlSiN wear-resistant layer with high Al and Si content is deposited with the thickness of 1 mu m, wherein the atomic percentage of Ti is 20 percentThe atomic percentage of Al was 33%, the atomic percentage of Si was 5%, and the atomic percentage of N was 42%.

Referring to fig. 16, in the present comparative example, the Al and Si contents were increased in gradient with the cooperation of the gradually changing tiaalsi target current and Ti target, the atomic percentage of Ti in the coating was gradually decreased from 50% to 20% along the thickness direction of the coating, the atomic percentage of Al was gradually increased from 0% to 33%, and the atomic percentage of N was maintained at 40% to 50%; the solid solubility of TiN in the FCC structure can be reduced by simultaneous doping of Al and Si elements, so that along with the increase of the content of the doping elements, the columnar structure of the coating is gradually transited to a glassy morphology without obvious characteristics, a large amount of amorphous is coated with a small amount of crystals (see figure 17), the hardness of the coating is only 24GPa due to a large amount of amorphous, the wear resistance is reduced, and the requirement of the wear resistance under the condition of high-speed cutting cannot be met.

In summary, aiming at the problems that the traditional coating has a columnar crystal structure due to single tissue structure, cracks are easy to generate and the service performance is deteriorated; when the content of the doping element is more, the residual stress is large, and the film base binding force is poor. The invention provides a gradient coating material, a preparation method and application thereof, which is a gradient coating imitating mussel structure and function and has the following effects:

(1) The coherent connection of the coating and the interface of the hard alloy substrate is realized through the design of the bonding layer structure, and the modulus of the film base material is matched, so that the bottom layer of the coating and the substrate are cooperatively deformed under load, and the cracking trend of the film base interface is reduced.

(2) The stress buffer layer is added to further release stress flexibly, so that high-strength and high-toughness connection of the film-based interface is realized; the content of doping elements is continuously increased in a layer-by-layer gradient manner, so that lattice distortion caused by element doping in the coating is gradually changed, and the coating stress accumulated in the single-layer structure due to high doping amount can be alleviated.

(3) As a result of the gradient change of the components, the elastic modulus and the hardness of the coating material are also changed in a gradient way, and the interface between layers has higher compatibility by coordinating the deformation and the gradient change of the components, so that the cracking risk of the interface between layers is reduced.

(4) The top layer structure of the high doping element can provide better performance for the coating, and meanwhile, the design of the gradient structure also ensures that the coating has better film base binding force and higher hardness, and the preparation of the high hard coating with large thickness can be realized.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The gradient coating material is characterized by comprising an adhesive layer, an intermediate transition layer and a top wear-resistant layer which are sequentially deposited on a hard alloy substrate, wherein the intermediate transition layer and the top wear-resistant layer both contain Ti, N and doping elements, the doping elements are silicon-aluminum mixtures, the content of the doping elements in the intermediate transition layer gradually increases from bottom to top, and the content of the doping elements in the top wear-resistant layer is equal to the content of the doping elements in the intermediate transition layer at the topmost part;

the intermediate transition layer is a TiAlSiN coating with gradually increased Si and Al contents, and the top wear-resistant layer is a TiAlSiN coating; gradually reducing the atomic percentage of Ti from 46-60% to 20-30%, gradually increasing the atomic percentage of Al from 0-2% to 10-30%, gradually increasing the atomic percentage of Si from 0-2% to 3-10%, and keeping the atomic percentage of N at 40-50% from the bottom to the top of the intermediate transition layer; in the top wear-resistant layer, the atomic percentage of Ti is 20% -30%, the atomic percentage of Al is 10% -30%, the atomic percentage of Si is 3% -10%, and the atomic percentage of N is 40% -50%.

2. The gradient coating material of claim 1, wherein the adhesive layer is selected from at least one of TiN, crN, zrN and VN.

3. The gradient coating material of claim 2, wherein the adhesion layer is a TiN coating.

4. The gradient coating material of claim 1, wherein the adhesive layer has a thickness of 20nm to 200nm, the intermediate transition layer has a thickness of 1 μm to 6 μm, and the top wear layer has a thickness of 1 μm to 3 μm.

5. The gradient coating material according to claim 4, wherein the content of doping elements in the coating is gradually increased in the deposition process of the intermediate transition layer, and the interlayer thickness is controlled to be 5-20 nm by regulating the thickness of the single layer according to the deposition time of each single layer.

6. The gradient coating material of claim 1, wherein the cemented carbide substrate is a sub-microcrystalline cemented carbide with a Co content of 8% -12% and WC grain size of 0.6 μm or less.

7. The gradient coating material of claim 1, wherein a buffer layer is further provided between the bond layer and the cemented carbide substrate.

8. The gradient coating material of claim 7, wherein the buffer layer is a Ti metal layer having a thickness of 10-100 nm.

9. The gradient coating material of claim 8, wherein the buffer layer has a thickness of 10-20 nm.

10. A method for preparing the gradient coating material as claimed in any one of claims 1 to 9, comprising: and sequentially depositing the bonding layer, the intermediate transition layer and the top wear-resistant layer on the hard alloy substrate.

11. The preparation method according to claim 10, characterized in that the preparation method comprises:

depositing an adhesive layer: introducing nitrogen into the furnace chamber, starting a Ti target material, and depositing the bonding layer on the hard alloy substrate;

depositing an intermediate transition layer: continuously introducing nitrogen into the furnace chamber, and simultaneously starting a Ti target and a Ti alloy target, wherein the current of the Ti target is kept unchanged, and the current of the Ti alloy target is gradually increased; then keeping the current of the Ti alloy target unchanged, wherein the current of the Ti alloy target gradually decreases;

the Ti alloy target is a TiAlSi alloy target, wherein the atomic mass ratio of Al is 35% -45% and the atomic mass ratio of Si is 5% -15%.

12. The method of claim 11, wherein prior to depositing the bond layer, the cemented carbide substrate is pre-treated to remove surface oxide films and contaminants, then the cemented carbide substrate is held in a furnace chamber and is evacuated and heated to 400-500 ℃, then an inert gas is introduced into the furnace chamber to bombard the etched substrate under negative bias and clean the surface.

13. The method according to claim 11, wherein the pressure in the furnace is controlled to be 0.5X10 when the adhesive layer is deposited ^-2 mbar~1.5×10 ^-2 The current of the Ti target is set to 110A-130A, and a negative bias voltage of 70V-90V is applied.

14. The method according to claim 11, wherein the gas pressure in the furnace is controlled to be 5.0X10 when the intermediate layer is deposited ^-2 mbar~7.0×10 ^-2 mbar, applying a negative bias voltage of 50V-70V, simultaneously starting a Ti target and a Ti alloy target, wherein the current of the Ti target is kept constant at 110A-130A, the current of the Ti alloy target is gradually increased from 80A-100A, and the increasing step length is1A-3A, wherein the time interval is adjusted to be 1 min-5 min; when the current of the Ti alloy target is increased to be the same as the current of the Ti alloy target, keeping the current of the Ti alloy target unchanged, gradually reducing the current of the Ti alloy target, wherein the step length of the reduction is 1A-3A, the time interval of adjustment is 1 min-5 min, and closing the Ti target until the current of the Ti alloy target is reduced to be consistent with the initial current of the Ti alloy target.

15. The method of claim 11, wherein the gas pressure in the furnace is controlled to be 5.0x10 during deposition of the top abrasion resistant layer ^-2 mbar~7.0×10 ^-2 Applying 40-60V negative bias voltage, setting the current of the Ti alloy target material to be 110-130A, setting the deposition time to be 15-25 min, closing the Ti alloy target material, stopping introducing nitrogen and closing the negative bias voltage.

16. The method of claim 11, wherein the Ti metal buffer layer is deposited prior to depositing the adhesion layer.

17. The method of claim 16, wherein an inert gas is introduced into the chamber during deposition of the Ti metal buffer layer, and the gas pressure is maintained at 0.5 x 10 ^-2 mbar~1.5×10 ^-2 And (3) mbar, starting the Ti target, setting the current of the Ti target to be 110A-130A, and applying a negative bias voltage of 70V-90V on the workpiece frame.

18. Use of a gradient coating material according to any one of claims 1 to 9 or a gradient coating material prepared by a preparation method according to any one of claims 10 to 17 in the preparation of a blade.