AU2021105054A4

AU2021105054A4 - Wear-resistant and Corrosion-resistant Nano-multilayer Protective Coatings on Titanium Alloy and Preparation Method Thereof

Info

Publication number: AU2021105054A4
Application number: AU2021105054A
Authority: AU
Inventors: Qimin WANG; Tengfei ZHANG
Original assignee: Guangdong University of Technology
Current assignee: Guangdong University of Technology
Priority date: 2021-08-06
Filing date: 2021-08-06
Publication date: 2021-10-07
Anticipated expiration: 2029-08-06

Abstract

The invention relates to a multilayer TiN/CrN coating with wear-resistant and corrosion resistant protection functions for titanium alloys and a preparation method thereof, belonging to the technical field of film materials. The nano-multilayer TiN/CrN hard coating is formed by alternately depositing and superposing TiN and CrN ceramic layers on a titanium alloy substrate according to a certain design structure by adopting an arc ion plating deposition technology. The coating consists of Ti metal transition layer, TiN transition layer and nano multilayer TiN/CrN. The modulation period of nano-multilayer TiN/CrN is 1-500 nm, and the total thickness of coating is 1-20 [m. The TiN/CrN hard coating provided by the invention is applied to the surface of titanium alloy, and integrates the respective advantages of TiN and CrN. Therefore, the TiN/CrN hard coating has high hardness, toughness, adhesion, wear resistance and corrosion resistance superior to those of each monolayer, thus expanding the application range of titanium alloy matrix in severe environment and prolonging its service life. Meanwhile, the arc ion deposition technology used for preparing the TiN/CrN coating with the special layered structure has the advantages of convenient operation, short preparation period, low cost and good reproducibility. Therefore, industrial mass production can be realized. 1/7 Alternated nlayers ______________ Large particles are n players coveredd b thenext layer-* ~The pinhole with the next layer Figure1I V(1 11) VTiN vCrN Q ~~ TiNCN :1 Ti alloy:: II H i I 25 30 35 40 45 50 55 60 65 70 75 80 85 90 206(degree) Figure 2

Description

1/7

Alternated nlayers

______________ Large particles are n players

coveredd b thenext layer-*

~The pinhole

with the next layer

Figure1I

V(1 11) VTiN

vCrN

Q ~~ TiNCN

:1 Ti alloy:: H II i I

25 30 35 40 45 50 55 60 65 70 75 80 85 90 206(degree)

Figure 2

Wear-resistant and Corrosion-resistant Nano-multilayer Protective Coatings on

Titanium Alloy and Preparation Method Thereof

TECHNICAL FIELD

The invention belongs to the technical field of surface protection technology and

related coating materials. The invention particularly relates to a wear-resistant and

corrosion-resistant nano-multilayer TiN/CrN coating for titanium alloy surface and a

preparation method thereof.

BACKGROUND

Titanium alloys have the advantages of low density, high specific strength and good

weldability. It is mainly used in aerospace and military industries. It is also widely

used in many industrial sectors such as chemical industry, petroleum, light industry,

metallurgy, power generation, sports and medical treatment. However, titanium alloy

has poor wear resistance and high friction coefficient, and is prone to adhesive wear.

Moreover, titanium alloy is prone to fretting wear and fretting fatigue at the junction

of vibrating components. Friction heat and friction at the interface will aggravate

fatigue failure and cause spalling damage. The oxidation resistance of titanium alloy

at high temperature above 600°C is poor. In addition, TC4 titanium alloy, i.e., Ti-6Al

4V, is composed of a+p phases, and a protective oxide film TiO2 is easily formed in

the air on the surface. Because the protective oxide film TiO2 is formed on the

surface, although the film has good corrosion resistance in oxidizing and neutral

media, this film is unstable in reducing or complexing media, such as sulfuric acid,

hydrochloric acid and fluoride-containing solutions. Among them, the activity in

reducing medium is due to the existence of P phase rich in V. Vanadium oxide is

soluble in acid, which in turn further reduces the corrosion resistance. Furthermore,

alloying elements (such as Al and V) can help to form a galvanic couple between a phase and P phase, thus reducing the corrosion resistance of the alloy. These problems limit the application of titanium and its alloys, and make the protection of its surface one of the research hotspots in recent years.

At present, the commonly used surface hardening treatment technologies of titanium

alloy include thermal spraying, electroplating and electroless plating, plasma

nitriding, laser cladding, vapor deposition, micro-arc oxidation and composite surface

treatment technologies, etc. For example, Zhou Dandan and others selected h-BN and

Ti3SiC2 as lubricants to prepare Ni-based self-lubricating wear-resistant and

antifriction coating on the surface of titanium alloy (TC4) by laser cladding. Although

the wear and corrosion resistance are improved to a certain extent, the cracks and

spalling problems of ceramic cladding coating are serious. Nano-TiO2was prepared

on titanium alloy surface by anodic oxidation process. Although it can effectively

improve the wear resistance, the anodic oxidation film structure is loose and porous,

which limits the improvement of corrosion resistance.

In this case, various hard coatings, such as nitrides of TiN, TiAlN and CrN, prepared

by common PVD technology provide better wear and corrosion resistance. Good

adhesion and few defects can reduce friction and wear of workpieces, effectively

improve surface hardness, toughness, wear resistance, high temperature stability and

corrosion resistance, greatly improve the service life of coating products, and meet the

stringent requirements of modern manufacturing industry for titanium alloy use

environment. In addition, multilayer films have better performance than monolayer

films. A large number of internal interfaces parallel to the substrate in multilayer films

can hinder crack propagation and provide dislocation motion resistance. Therefore,

while increasing the toughness, the hardness and strength of the film are also

improved. The coating prepared by physical vapor deposition is almost embedded with defects, and it is impossible to completely avoid the formation of pinholes. When the coating grows in the form of columnar crystals, the columnar crystal gaps will inevitably become the weak area of corrosion resistance of the coating. When the coating material is exposed to aqueous solution, local galvanic corrosion will occur, resulting in accelerated attack. However, nano-multilayer structure can re-nucleate multiple layers. Each layer fills the defects of the previous layer to form a dense coating structure, thus avoiding defects, pinholes and columnar crystal gaps between each layer. Therefore, with the development of new coating materials, using nano coating structure can reduce and eliminate the defects in the deposition process and improve the corrosion resistance of the coating.

TiN and CrN films have high hardness and wear resistance, and excellent oxidation

resistance and corrosion resistance at high temperature. They can not only be used as

wear-resistant coatings for surface strengthening of tools and dies and cutting tools,

but also have important applications in many industrial fields such as surface

anticorrosion and decoration. Considering the friendly interface with titanium alloy

substrate and performance matching, it is a good choice to use multilayer TiN/CrN

film system as surface strengthening layer. The reason is that CrN has excellent

performance in wear resistance and corrosion resistance, while TiN film is the most

basic hard film material, which contains the same element (Ti) as the substrate and

has a low lattice mismatch with CrN film. TiN film has advantages in reducing the

internal stress of the film, increasing toughness, hardness and adhesion of the film.

Although a large number of researchers have done research on multilayer TiN/CrN

films, the research on the methods used, the selected substrates and their wear and

corrosion resistance needs further development. For example, Yaomin Zhou et al.

prepared nano-multilayer TiN/CrN films on WC/Co cemented carbide by magnetron sputtering to study the influence of modulation period (modulation period refers to the thickness of alternating layers circulating once in nano-multilayer, that is, the thickness of a layer of TiN and a layer of CrN) on wear resistance. They found that the film has an optimal wear resistance under a certain modulation period. J.J. Roa et al. used multi-arc ion plating to prepare nano-multilayer TiN/CrN films on high speed steel, and found their excellent adhesion and hardness and so on.

According to the invention, the nano-multilayer TiN/CrN film is prepared by the arc

ion plating technology. The wear resistance and corrosion resistance of the coating are

simultaneously studied under the condition of studying the phase composition,

mechanical properties (high hardness, high adhesion) and surface morphology. A

practical hard film with high wear resistance and corrosion resistance is obtained by

applying the coating itself and multiple structural advantages to titanium alloy.

Therefore, the application range of the matrix titanium alloy is expanded and the

service life is prolonged. The nano-multilayer TiN/CrN film can be applied to many

parts used in corrosive environment with friction, and the surface protection of

titanium alloy is of great significance.

SMMMARY

In order to solve the shortcomings and deficiencies of titanium alloy in the application

fields of aerospace, offshore operation and the like, the primary object of the

invention is to provide a multilayer hard protective coating which has excellent

comprehensive characteristics such as high hardness, low stress, high wear resistance,

corrosion resistance, strong film-base bonding and the like and can be applied to the

surface of titanium alloy. That is to say, the combination of TiN and CrN is adopted,

and TiN layers and CrN layers are alternately deposited on the substrate to form a

nano-layered structure with high wear resistance and high corrosion resistance. The wear resistance and corrosion resistance of the coating are studied together to expand the application of nano-multilayer TiN/CrN coating in titanium alloy protection and industry, and promote the development of titanium alloy surface protection.

Another object of the present invention is to provide a preparation method of the

nano-multilayer TiN/CrN coating with the multilayer layered structure. The

preparation method has the advantages of stable product performance, convenient

operation, simple process, short preparation period, low cost, environmental

protection, and convenience for large-scale industrial production.

The object of that invention is realize by the following technical scheme.

A TiN/CrN coating with nano-multilayer layered structure is formed by taking a

titanium target and a chromium target as raw materials, and reacting and depositing

multi-arc ions with nitrogen gas in a cavity to form a TiN/CrN coating with a nano

layered structure which is superposed by a titanium nitride layer and a chromium

nitride layer.

Preferably, the chromium target and the zirconium target are both planar target,

wherein the purity of the titanium target and the chromium target are both 99.95%.

Preferably, the substrate is TC4 titanium alloy.

Preferably, the above-mentioned preparation method of multilayer TiN/CrN coating is

characterized in that it takes a metal Ti target and a metal Cr target as raw materials,

adopts arc ion plating technology for preparation, and primes a Ti metal layer and TiN

as transition layers, so that the multilayer TiN/CrN coating has better adhesion. The

specific steps are as follows.

al) Cleaning the substrate: sending the polished substrate into an ultrasonic cleaning

machine. Sequentially carrying out ultrasonic cleaning for 10 min-20 min with acetone and absolute ethyl alcohol at 15 kHz-30 kHz respectively. Then cleaning with deionized water, and then blow-drying with nitrogen gas with purity > 99.5%.

a2) Vacuumizing and plasma etching to clean the coating chamber: placing the

substrate after ultrasonic cleaning on the workpiece support of the vacuum chamber.

Heating the working temperature of the deposition chamber to 300-500°C, heating the

substrate to 300-500°C. Extracting gas from the deposition chamber. Pumping to a

vacuum degree below 5.Ox10- Pa. The heating power is 4 kW-8 kW.

Preferably, in the step a2), the substrate is applied with bias voltage at -60 V to

120 V, argon gas of 150 sccm-250 seem and krypton gas of 100 sccm-250 seem is

introduced for etching for 40 minutes to clean the substrate. The ion etching time is 30

to 60 minutes.

a3) Depositing a Ti primer layer: turning on the power supply of the arc Ti target,

with the arc source current of 60 A-150 A. Introducing argon gas of 200 sccm-600

seem, controlling the vacuum chamber pressure at 0.6 Pa-1.5 Pa, maintaining the

furnace temperature at 350°C-450°C, and depositing for 20-40 min. The substrate is

applied with negative bias voltage of -60 V-150 V, the duty ratio is 10%-80%, and the

heating power is 4 kW-8 kW.

a4) Depositing a TiN layer: continuously turning on the power supply of the arc

Ti target, with the arc source current of 60 A-150 A. Introducing nitrogen gas of 200

sccm-400 seem, controlling the vacuum chamber pressure at 0.6 Pa-1.5 Pa,

maintaining the furnace temperature of 350°C-450°C, and depositing for 20-40 min.

The substrate is applied with negative bias voltage of -60 V-150 V, the duty ratio is

%-80%, and the heating power is 4 kW-8 kW.

a5) Depositing a TiN/CrN nano-structure coating: turning on an arc Cr target and

a Zr target. Introducing nitrogen gas of 200 sccm-400 secm, controlling the vacuum chamber pressure at 0.6 Pa-1.5 Pa, maintaining the furnace temperature at 350-450°C, and depositing for 1-10 h. The substrate is applied with negative bias voltage of -60

V-150 V, the duty ratio is 10%-80%, and the heating power is 4 kW-8 kW.

a6) After the deposition is finished, turn off the power supply. When the temperature

of the vacuum chamber drops to room temperature, open the vacuum chamber to take

out the substrate. The coating formed on the surface of the substrate is the TiN/CrN

coating with nano-layered structure.

Preferably, the substrate is a sample TC4 to be coated. The parameters of the turntable

support in steps a2)-a5) are as follows. The support rotates 1.5-15 rpm/min and

revolves 0.5-5 rpm/min. The distance between the target and the substrate is 2-20 cm.

The above-mentioned TiN/CrN coating with nano-multilayer layered structure can be

applied to the surface protection of titanium alloy. The surface protection of metal

mechanical parts, precision dies, precision transmission machinery, bearings, valves,

electronic products, decorative products and materials can also be applied. The nano

multilayer TiN/CrN coating prepared by the invention has high hardness, high wear

resistance and corrosion resistance. The preparation method is simple and

controllable, the preparation period is short, the cost is low. The nano-multilayer

TiN/CrN coating can be applied to harsh environments and is completely suitable for

surface protection of TC4 titanium alloy.

The principle of the invention is that the alternating multilayer is formed by the

rotation of the support. When the sample is facing the metal target, the target surface

is instantaneously ionized and then reacts with nitrogen gas ions in the chamber under

the attraction of negative bias voltage, and the corresponding nitride film is deposited

on the surface of the substrate. Ti primer layer and TiN transition layer are mainly

used to improve the adhesion between the film and titanium alloy (TC4) matrix. nano- multilayer TiN/CrN can reduce the internal stress of the film and improve the density, toughness, hardness, wear resistance and corrosion resistance of the film.

Compared with the prior art, the invention has the following advantages and

beneficial effects.

A nano-structured coating is prepared by utilizing the performance advantages of

monolayer TiN coating and CrN coating. By controlling the rotation speed of the

substrate support, a nano-multilayer structure with TiN coating and CrN coating

alternated periodically is formed. The residual stress is reduced, the toughness of the

coating is enhanced, and meanwhile the adhesion between the coating and the

substrate is enhanced, and the wear resistance and corrosion resistance of the coating

are improved, so that TC4 titanium alloy is more suitable for more severe application

environments.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 A schematic diagram of microstructure of nano-multilayer TiN/CrN structure

coating provided in Embodiment 1 of the present invention

Figure 2 A XRD pattern of the nano-multilayer TiN/CrN structure coating provided in

Embodiment 1 of the present invention and TiN and CrN monolayer coatings

provided in Comparative embodiments 4-5 and substrate

Figure 3 A SEM topography of the nano-multilayer TiN/CrN structure coating

provided in Embodiment 1 of the present invention, wherein (a) is a cross-sectional

topography; (b) is a surface topography

Figure 4 A scratch diagram of the nano-multilayer TiN/CrN structure coating

provided in Embodiment 1 of the present invention and the TiN and CrN monolayer

coatings provided in Comparative embodiments 4-5

Figure 5 A comparative diagram of hardness, elastic modulus and H/E value of nano

multilayer TiN/CrN structure coating provided in Embodiment 1 of the present

invention and TiN and CrN monolayer coatings provided in Comparative

embodiments 4-5

Figure 6 The friction coefficients of the nano-multilayer TiN/CrN structure coating

provided in Embodiment 1 of the present invention and the TiN and CrN monolayer

coatings provided in Comparative embodiments 4-5

Figure 7 The 3D wear mark morphology of the nano-multilayer TiN/CrN structure

coating provided in Embodiment 1 of the present invention and the TiN and CrN

monolayer coatings provided in Comparative embodiments 4-5

Figure 8 A bar graph of wear rate of the nano-multilayer TiN/CrN coating provided in

Embodiment 1 of the present invention and TiN and CrN monolayer coatings

provided in Comparative embodiments 4-5

Figure 9 A corrosion polarization curve of nano-multilayer TiN/CrN structure coating

provided in Embodiment 1 of the present invention and substrate in 3.5% NaCl

solution at room temperature using a three-electrode system (Ag/AgC1 as reference

electrode)

DESCRIPTION OF THE INVENTION

In order to describe the technical scheme of the present invention more clearly and

completely, the present invention will be further explained in detail by specific

embodiments below. It should be understood that the specific embodiments described

here are only used to explain the present invention, not to limit the present invention,

and various changes can be made within the scope defined by the claims of the

present invention.

Embodiment 1

A nano-multilayer TiN/CrN coating comprises a substrate and alternately deposited

TiN layers and CrN layers. The coating thickness is 5.45 [m, and the modulation

period is 46nm.

The method is realized according to the following steps.

Sending the polished titanium alloy (TC4) substrate into an ultrasonic cleaning

machine. Sequentially carrying out ultrasonic cleaning for 10 min with acetone and

absolute ethyl alcohol at 30 kHz respectively. Then cleaning with deionized water,

and then blow-drying with nitrogen gas with purity > 99.5%. Placing the substrate

after ultrasonic cleaning on a workpiece support of a vacuum chamber, heating the

working temperature of a deposition chamber to 422°C, heating the substrate to

420°C, and extracting gas in the deposition chamber. Pumping to a vacuum degree

below 5.0x10- Pa. The heating power is 8 kW. Applying a bias voltage of -80V to the

substrate, and introducing 150 seem argon and 100 seem krypton for etching for 40

minutes to clean the substrate. Turning on the power supply of the arc Ti target, with

the arc source current of 70 A-80 A. Introducing argon gas of 308 secm, controlling

the vacuum chamber pressure at 1 Pa, maintaining the furnace temperature at 415°C,

and depositing for 20-40 min. The substrate is applied with negative bias voltage of

V-150 V, the duty ratio is 10%-80%, and the heating power is 4 kW-8 kW.

Continuously turning on the power supply of the arc Ti target, with the arc source

current of 70 A-80 A. Introducing nitrogen gas of 293.5 secm, controlling the vacuum

chamber pressure at 1 Pa, maintaining the furnace temperature of 407°C, and

depositing for 20-40 min. The substrate is applied with negative bias voltage of -90 V,

the duty ratio is 80%, and the heating power is 8 kW. Turning on the arc Ti target and

Cr target, introducing nitrogen gas of 308.2 secm, controlling the vacuum chamber

pressure at 1 Pa, maintaining the furnace temperature at 395°C, and depositing for 4 hours. The substrate is applied with negative bias voltage of -90 V, the duty ratio is

%, and the heating power is 8 kW. After the deposition is finished, turn off the

power supply. When the temperature of the vacuum chamber drops to room

temperature, open the vacuum chamber to take out the substrate. The coating formed

on the surface of the substrate is a TiN/CrN coating with nano-layered structure.

During the whole coating process, the support rotates 1.5 rpm/min and revolves 0.5

rpm/min. The distance between the target and the substrate is 12 cm.

Embodiment 2

The coating described in Embodiment 2 is basically the same as that in Embodiment

1. The difference is that the rotation speed is different. The support rotates at 3

rpm/min and revolves at 1 rpm/min, the coating thickness is 5.9 [Lm, and the

modulation period is 18.2 nm.

Embodiment 3

The coating of Embodiment 3 is basically the same as that of Embodiment 1. The

difference is that the modulation period of the coating is different when the support

rotates at 6 rpm/min and revolves at 2 rpm/min. The coating thickness is 4.9 m and

the modulation period is 8.9 nm.

Comparative embodiment 4

In order to verify the superiority of nano-multilayer TiN/CrN coating, a set of

monolayer TiN coating is specially made as a control test. The specific steps of the

control test are basically the same as those in Embodiment 1. The difference is that

only the Ti target is turned off and only the monolayer TiN coating is plated in the

multilayer plating step.

Comparative embodiment 5

In order to verify the superiority of nano-multilayer TiN/CrN coating, a set of

monolayer CrN coatings was specially made as a control test. The specific steps of the

control test are basically the same as those of Embodiment 1. The difference is that

only the Cr target was turned off and only the monolayer CrN coating was plated in

the multilayer plating step.

XRD detection is carried out on the coatings of the invention. As shown in Figure 2, it

is analyzed that the composition phases of the nano-multilayer TiN/CrN coating are

TiN and CrN. The (111) crystal plane grows preferentially. As shown in Figure 3,

SEM observed the morphology and structure of nano-multilayer TiN/CrN coating,

and made a nano-multilayer schematic diagram, as shown in Figure 1. The

performances of the nano-multilayer TiN/CrN structure coating provided in

Embodiment 1 of the present invention were tested and compared accordingly by the

following steps. Testing the film-substrate adhesion of the coating by a scratch tester,

testing the hardness by a nano indentor, researching the wear resistance of the coating

by a friction and wear tester, and testing the corrosion resistance of the coating by an

electrochemical workstation. Figure 4 is a scratch diagram comparing the nano

multilayer TiN/CrN structure coating provided in Embodiment 1 of the present

invention with the monolayer coatings of Comparative embodiments 4-5. Figure 5 is a

comparative diagram of hardness, elastic modulus and H/E value of nano-multilayer

TiN/CrN structure coating provided in Embodiment 1 of the present invention and

TiN and CrN monolayer coatings provided in Comparative embodiments 4-5. Figure

6 shows the friction coefficients of the nano-multilayer TiN/CrN structure coating

provided in Embodiment 1 of the present invention and the TiN and CrN monolayer

coatings provided in Comparative embodiments 4-5. Figure 7 is the 3D wear mark

morphology of the nano-multilayer TiN/CrN structure coating provided in

Embodiment 1 of the present invention and the TiN and CrN monolayer coatings

provided in Comparative embodiments 4-5. Figure 8 is a bar graph of wear rate of

nano-multilayer TiN/CrN coating provided in Embodiment 1 of the present invention

and TiN and CrN monolayer coatings provided in Comparative embodiments 4-5.

Figure 9 is a corrosion polarization curve of nano-multilayer TiN/CrN structure

coating and substrate in 3.5% NaCl solution at room temperature using a three

electrode system (Ag/AgC1 as reference electrode).

It can be seen from Figure 4 that the nano-multilayer TiN/CrN structure provided in

Embodiment 1 of the present invention has better adhesion with the substrate than the

monolayer. It can be seen from Figure 5 that the nano-multilayer TiN/CrN provided in

Embodiment 1 of the present invention has higher hardness and H/E, i.e., better

resistance to crack deformation than the monolayer coating. It can be seen from

Figure 6-8 that the nano-multilayer TiN/CrN coating provided in Embodiment 1 of

the present invention has a relatively low friction coefficient, and the wear resistance

is greatly improved, so that almost no wear marks can be seen in 3D morphology. The

nano-multilayer TiN/CrN greatly protects the matrix titanium alloy. It can be seen

from Figure 9 that the self-corrosion potential of the nano-multilayer TiN/CrN

provided in Embodiment 1 is obviously increased, the self-corrosion current is

reduced. The nano-multilayer TiN/CrN has better corrosion resistance and can

effectively protect the substrate in corrosion solution.

The above-mentioned embodiments of the present invention are only examples to

clearly illustrate the present invention, but are not a limitation of the practical mode of

the present invention. For those of ordinary skill in the field, other changes in

different forms can be made on the basis of the above description. All embodiments

need not be exhaustive here. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A wear-resistant and corrosion-resistant multilayer TiN/CrN coating on the

surface of titanium alloy and a preparation method thereof, characterized in that the

TiN/CrN coating takes a metal titanium target and a metal chromium target as raw

materials, and comprises a Ti layer and a TiN primer layer and a nano-multilayer

TiN/CrN coating which are sequentially deposited on the surface of a titanium alloy

substrate from bottom to top.

2. The wear-resistant and corrosion-resistant multilayer TiN/CrN coating according to

Claim 1, characterized in that the chromium target and the zirconium target are both

planar targets, and the purity of the chromium target and the zirconium target is

99.95%.

3. The preparation method of the multilayer TiN/CrN coating according to any one of

Claim 1-2, characterized by specifically comprises the following steps:

machine, sequentially carrying out ultrasonic cleaning for 10 min-20 min with acetone

and absolute ethyl alcohol at 15 kHz-30 kHz, then cleaning with deionized water, and

then blow-drying with nitrogen gas with purity > 99.5%;

a2) vacuumizing and plasma etching to clean the coating chamber: placing the

substrate after ultrasonic cleaning on the workpiece support of the vacuum chamber,

substrate to 300-500°C, and extracting gas from the deposition chamber; pumping to a

vacuum degree below 5.Ox10-3 Pa, the heating power is 4 kW-8 kW, applying a bias

voltage of -60 V-120 V to the substrate, introducing argon gas of 150 sccm-250 seem

and krypton gas of 100 sccm-250 seem for etching for 40 minutes to clean the

substrate, and the plasma etching time is 30-60 min.

introducing argon gas of 200 sccm-600 secm, controlling the vacuum chamber

pressure at 0.6 Pa-1.5 Pa, maintaining the furnace temperature at 350°C-450°C, and

depositing for 20-40 min; the substrate is applied with negative bias voltage of -60 V

150 V, the duty ratio is 10%-80%, and the heating power is 4 kW-8 kW.

a4) depositing a TiN layer: continuously turning on the power supply of the arc Ti

target, with the arc source current of 60 A-150 A, introducing nitrogen gas of 200

sccm-400 seem, controlling the vacuum chamber pressure at 0.6 Pa-1.5 Pa,

maintaining the furnace temperature at 350°C-450°C, and depositing for 20-40 min;

%-80%, and the heating power is 4 kW-8 kW.

a5) depositing a TiN/CrN nano-structure coating: turning on an arc Ti target and a Cr

target, introducing nitrogen gas of 200 sccm-400 secm, controlling the vacuum

chamber pressure at 0.6 Pa-1.5 Pa, maintaining the furnace temperature at 350-450°C,

and depositing for 1-10 h; the substrate is applied with negative bias voltage of -60 V

150 V, the duty ratio is 10%-80%, and the heating power is 4 kW-8 kW;

a6) after the deposition is finished, turn off the power supply, and when the

temperature of the vacuum chamber drops to room temperature, open the vacuum

chamber to take out the substrate, and the coating formed on the surface of the

substrate is the TiN/CrN coating with nano-layered structure.

4. The preparation method according to Claim 4, characterized in that the substrate in

the step al) is a sample TC4 titanium alloy to be coated; the parameters of the

turntable support in the steps a2)-a5) are as follows: the support rotates 1.5-15

rpm/min and revolves 0.

5-5 rpm/min; the distance between the target and the

substrate is 2-20 cm.