CN115584470A - A method for improving corrosion and wear resistance of titanium alloy surface through Zr/Zr2N/ZrN multilayer coating - Google Patents

Abstract

The invention relates to the technical field of coating preparation, in particular to a method for improving the corrosion and wear resistance of a titanium alloy surface through a Zr/Zr ₂ N/ZrN multilayer coating. The Zr intermediate layer can reduce coating defects and improve coating compactness , and can preferentially produce a passivation film, hinder the diffusion of corrosive media, and improve the corrosion resistance of the coating; at the same time, the Zr metal layer can inhibit crack growth, and the joint improvement of corrosion and toughness improves the wear of the coated medical titanium alloy in a corrosive environment Performance, the wear rate of Zr/Zr2N/ZrN multilayer coating on titanium alloy surface (4.69×10 ^‑6 mm ³ (Nm) ^‑1 ), compared with that of single layer coating (1.46×10 ^‑5 mm ³ (Nm) ^‑1 ), decreased by an order of magnitude, and the average current density of the multilayer coating (1.19×10 ^‑8 A/cm ² ) was lower than that of the single layer coating (3.19×10 ^‑8 A/cm 2 ) when simulating the corrosion of human body fluids cm ² ) is 3 times lower, and the corrosion resistance of multi-layer coatings is significantly better than that of single-layer coatings.

Description

A Zr/Zr2N/ZrN multilayer coating to improve the corrosion and wear resistance of titanium alloy surface able method

technical field

The invention relates to the technical field of coating applications, in particular to a method for improving the corrosion and wear resistance of titanium alloy surfaces through Zr/Zr ₂ N/ZrN multilayer coatings.

Background technique

Titanium alloy (Ti-6Al-4V) is one of the three major biomedical metals. Compared with stainless steel and Co-Cr-Mo alloy, the Young's modulus of titanium alloy is only half of the two, and it is more suitable for cortical bone. In addition, titanium alloy has good mechanical properties and biocompatibility, and the dense oxide film formed on the surface can effectively deal with the corrosion caused by the human body fluid environment. At present, artificial joint prostheses, fracture internal fixators and orthopedic devices made of titanium alloys are widely used clinically and become the most representative biomedical metal materials. However, while titanium alloys are corroded by body fluids in the human body environment, they also face reciprocating friction between bone implants. Under the interaction of corrosion and friction, the surface loss of titanium alloys is serious. And the Al and V ions released by the titanium alloy will have certain toxic and side effects on the surrounding tissues. Therefore, for the practical significance of the safe use of titanium alloys in the human body, it is very important to improve their corrosion resistance and friction resistance.

At present, preparing a hard coating on the surface of titanium alloy is one of the most effective methods to solve the low surface hardness and poor wear resistance of titanium alloy. As a non-biotoxic, corrosion-resistant, and cytocompatible metal, Zr has been widely used in biomedicine. ZrN coatings prepared by physical vapor deposition (PVD) technique performed well in practical applications. However, there are many structural defects in PVD coatings, which easily lead to localized corrosion, especially pitting corrosion. Small pits or deep holes formed by pitting corrosion can cause great damage to the coating.

In view of the above-mentioned defects, the creator of the present invention has finally obtained the present invention through long-term research and practice.

Contents of the invention

The purpose of the present invention is to solve the problem that there are many structural defects in the ZrN coating on the surface of the titanium alloy, which is easy to cause local corrosion, especially pitting corrosion, and the small pits or deep holes formed by pitting corrosion will cause great damage to the coating. A method to improve the corrosion and wear resistance of titanium alloy surface by Zr/Zr ₂ N/ZrN multilayer coating was proposed.

In order to achieve the above object, the present invention discloses a method for improving the corrosion and wear resistance of the titanium alloy surface through a Zr/Zr ₂ N/ZrN multilayer coating, comprising the following steps:

S1, Ultrasonic cleaning and drying of titanium alloy samples;

S2, placing the titanium alloy pattern processed in step S1 on the substrate turret, heating and vacuuming, introducing argon gas, opening the Ti target, performing ion bombardment on the surface of the substrate, and cleaning the surface of the substrate by ion etching, Simultaneously activate the substrate;

S3, after the ion etching in step S2 is completed, keep the deposition temperature and the pressure of the furnace chamber constant, open the Zr target, and deposit the metal Zr layer;

S4, after the deposition of the Zr metal layer in step S3 is completed, keep the deposition temperature constant, turn off the argon gas, inject nitrogen gas, and deposit the Zr ₂ N transition layer;

S5, after the deposition of the Zr ₂ N transition layer in step S4 is completed, keep the deposition temperature constant, continue to feed nitrogen gas, and deposit the ZrN layer;

S6, repeating steps S3-S5, alternately depositing Zr metal layer, Zr ₂ N transition layer and ZrN layer to obtain a titanium alloy with Zr/Zr ₂ N/ZrN multi-layer coating deposited on the surface.

In the step S2, the flow rate of the argon gas is 200-600 sccm, the negative bias voltage of the substrate is -200V, and the ion etching time is 40 min.

In the step S3, the substrate bias voltage is -60-80V, the target current of the metal Zr target is 100-130A, and the deposition time is 5-10 minutes.

In the step S4, the pressure after the nitrogen gas is introduced is 1-2 Pa, the flow rate of the nitrogen gas is 100-300 sccm, and the deposition time is 2-4 minutes.

In the step S5, after continuing to feed nitrogen gas, the pressure is 2-5 Pa, the flow rate of N ₂ is 400-800 sccm, and the deposition time is 10-15 min.

The number of alternate depositions of the Zr metal layer, the Zr ₂ N transition layer and the ZrN layer in the step S6 is 7 times.

In the step S3, the pressure after nitrogen gas is introduced is 1-2 Pa, the flow rate of nitrogen gas is 100-300 sccm, and the deposition time is 2-4 min.

In the step S4, after continuing to feed nitrogen gas, the pressure is 2-5 Pa, the flow rate of N ₂ is 400-800 sccm, and the deposition time is 10-15 min.

The number of alternate depositions of the Zr metal layer, the Zr ₂ N transition layer and the ZrN layer in the step S5 is 7 times.

The Zr/Zr ₂ N/ZrN multilayer coating in the step S6 includes a plurality of Zr/Zr ₂ N/ZrN coating units, and the Zr/Zr ₂ N/ZrN coating units include metal Zr layers, Zr ₂ N transition layer and ceramic ZrN layer, the thickness of the Zr/Zr ₂ N/ZrN coating unit is 3 μm.

The thickness ratio of the metal Zr layer and the ceramic ZrN layer is 1:3, and the thickness of a single metal Zr layer is 110 nm.

Compared with the prior art, the beneficial effects of the present invention are:

1. Compared with the single-layer ZrN coating, the Zr/Zr ₂ N/ZrN multilayer composite coating on the surface of the titanium alloy prepared by the present invention has a denser coating structure, and the addition of the metal Zr layer interrupts the columnar growth of the ZrN crystal, The diffusion channels of corrosive media are reduced, which can improve the corrosion resistance of the titanium alloy surface.

2. The ZrO ₂ passivation film formed by the metal Zr intermediate layer in the Zr/Zr ₂ N/ZrN multilayer composite coating can inhibit the further diffusion of the corrosive medium, and the passivation film can block defects such as cracks and holes in the coating, Prevent the corrosive medium from penetrating into the titanium alloy substrate, greatly improving the corrosion resistance of the coating;

3. The multi-layer structure releases the internal stress of the coating. The softer metal Zr layer and the hard ceramic ZrN layer work together to show excellent friction resistance, and the corrosion products generated by the metal Zr layer participate in the friction process, which plays a certain role. Compared with single-layer coating, the corrosion and wear rate of multi-layer coating is greatly reduced.

Description of drawings

Fig. 1 is the schematic diagram of multilayer composite coating of the present invention;

Fig. 2 is the FESEM picture of single-layer coating and multi-layer composite coating cross-section;

Fig. 3 is the XRD spectrum of single-layer coating and multi-layer composite coating;

Fig. 4 is (a) impedance spectrum and (b) Bode figure of single-layer coating and multilayer composite coating;

Fig. 5 is the zeta potential polarization curve of single-layer coating and multi-layer composite coating;

Fig. 6 is the secondary ion mass spectrum signal spectrum after the electrochemical experiment of single-layer coating and multi-layer composite coating;

Figure 7 is the open circuit potential and friction coefficient of the single-layer coating and the multi-layer composite coating in the corrosion friction test;

Figure 8 is the three-dimensional topography of wear scars measured after (a) single-layer coating and (b) multi-layer coating corrosion friction test;

Fig. 9 is the average friction coefficient and wear rate of single-layer coating and multi-layer composite coating after corrosion friction;

Fig. 10 is a TEM image of the multi-layer composite coating of the present invention after abrasion failure.

detailed description

The above and other technical features and advantages of the present invention will be described in more detail below in conjunction with the accompanying drawings.

Example 1

(1) The Ti-6Al-4V titanium alloy material after grinding and polishing is ultrasonically cleaned for a certain period of time, rinsed with deionized water, and dried for later use;

(2) Place the processed titanium alloy pattern on the substrate turret, heat to 380°C, evacuate to 10 ^-4 Pa, pass in Ar gas, the Ar gas flow rate is 400 sccm, turn on the Ti target, and control the negative bias -200V, perform ion bombardment etching cleaning, etching time 40min;

(3) Keep the deposition temperature constant, further increase the N ₂ gas, change the pressure to 5 Pa, and the N ₂ flow rate to 800 sccm, to deposit the ZrN layer. The deposition time is 100 min, and the deposition of the ZrN layer is completed.

Example 2

(1) The Ti-6Al-4V titanium alloy material after grinding and polishing is ultrasonically cleaned for a certain period of time, rinsed with deionized water, and dried for later use;

(2) Place the processed titanium alloy pattern on the substrate turret, heat to 380°C, evacuate to 10 ^-4 Pa, pass in Ar gas, the Ar gas flow rate is 400 sccm, turn on the Ti target, and control the negative bias -200V, perform ion bombardment etching cleaning, etching time 40min;

(3) Maintain the deposition temperature, turn on the Zr target, and deposit the metal Zr layer; the substrate bias is -60, and the target current of the metal Zr target is 130A, and the deposition is completed after 5 minutes.

(4) Keep the deposition temperature constant, turn off the Ar gas, feed a small amount of N ₂ gas, change the pressure to 1 Pa, and the N ₂ flow rate to 100 sccm to deposit the Zr ₂ N transition layer. Deposition time is 2min;

(5) Keep the deposition temperature constant, further increase the N ₂ gas, change the pressure to 5 Pa, and the N ₂ flow rate to 800 sccm to deposit the ZrN layer. The deposition time is 15 min, and the deposition of the ZrN layer is completed.

(6) The above process is repeated, and the Zr metal layer, the Zr ₂ N transition layer and the ZrN layer are alternately deposited 7 times.

Fig. 1 is a schematic diagram of the multilayer composite coating of the present invention. It can be seen from the figure that the coating includes a multilayer structure of Zr, Zr ₂ N and ZrN.

Figure 2(a) and Figure 2(b) are FESEM images of the prepared ZrN single-layer coating and Zr/Zr ₂ N/ZrN multi-layer coating respectively. It can be seen from the figure that the Zr/Zr ₂ N/ZrN multi-layer The layer structure is denser, the defects in the coating are greatly reduced, and the coating quality is obviously better than that of a single-layer coating.

Figure 3 shows the XRD patterns of the single-layer coating and the multi-layer coating. It can be seen from the figure that in addition to the metal Zr and ZrN phases, Zr ₂ N phase also appears in the multi-layer coating. The existence of the Zr ₂ N phase improves the binding force between the metal Zr intermediate layer and the ceramic ZrN layer, and the toughness of the coating is stronger. In addition, compared with the single-layer coating, the peak intensity of the ZrN(200) surface of the multi-layer coating is reduced and shifted to a high angle, which proves that the grains of the multi-layer coating are refined and the internal stress of the coating is released, which can Better respond to the corrosive friction environment in the human body.

Figures 4(a) and 4(b) are the electrochemical impedance spectra and Bode diagrams of single-layer coatings and multi-layer coatings respectively. It can be seen that the Nyquist curve capacitance arc diameter of multi-layer coatings is significantly larger than that of single-layer coatings. Larger, and the phase angle of the Bode diagram is closer to 90°, and the |Z| value is higher. These all indicate that the multi-layer coating has a greater resistance value than the single-layer coating, and has better corrosion resistance in the face of SBF solution corrosion.

Figure 5 shows the potentiodynamic polarization curves of single-layer coating and multi-layer coating. The current density in the anodic region of the single-layer coating rises sharply, which means that the coating is anodically dissolved in the SBF solution, and the corrosion resistance of the coating is poor. However, the multilayer coating has obvious passivation area, and the average current density of the multilayer coating (1.19×10 ^-8 A/cm ² ) is lower than that of the single layer coating (3.19×10 ^-8 A/cm ² ) 3 times, the corrosion resistance of multi-layer coatings is significantly better than that of single-layer coatings.

Fig. 6 is the secondary mass spectrometry depth profiling spectrum of single-layer coating and multi-layer coating after electrochemical test. By comparing the O ^- and Cl ^- signals of the two coatings, it can be known that the single-layer coating has many defects inside the coating, and the SBF solution reaches the depth of the coating through these internal channels, causing corrosion damage in the coating , so O ^- and Cl ^- signals can still be detected in large quantities inside the monolayer coating. This is because there are a large number of corrosion holes inside the single-layer coating, and this corrosion behavior is catastrophic to the damage of the coating. For the Zr/Zr ₂ N/ZrN multilayer coatings improved by the Zr interlayer, in the corrosion experiment simulating the human body environment, the multilayer coating has optimized the coating structure due to the insertion of the metal Zr layer, and obtained a dense structure. and fewer defects, which effectively hinder the passage of the electrolyte. At the same time, the Zr metal layer can preferentially produce a ZrO ₂ passivation film, which hinders the diffusion of the corrosive medium. There are almost no O ^- and Cl ^- signals inside the coating, which is important for the coating Corrosion resistance had a positive impact.

Figure 7 shows the variation of the open circuit potential OCP and the coefficient of friction COF with time during the corrosion and friction process of single-layer coatings and multi-layer coatings. Figure 8 is the three-dimensional topography of the wear scars measured after the corrosion friction test of the single-layer coating and the multi-layer coating. Figure 9 shows the average friction coefficient and wear rate measured after the corrosion friction test of single-layer coating and multi-layer coating. It can be concluded from Fig. 7, Fig. 8 and Fig. 9 that the single-layer coating exhibits a higher average friction coefficient (0.72) and wear rate (1.46×10 ^-5 mm ³ (Nm) ^-1 ), while the Zr interlayer The improved Zr/Zr ₂ N/ZrN multilayer coating has a low average friction coefficient (0.51) and wear rate (4.69×10 ^-6 mm ³ (Nm) ^-1 ).

Figure 8 is an illustration showing that the wear marks of the single-layer coating are very deep. This is because the coating structure is loose and there are many defects. Due to the deep grinding pit, the particles cannot be discharged in time, causing severe abrasive wear in the grinding pit. The multi-layer coating has a denser structure, better wear resistance, shallower grinding pits, and easier discharge of wear debris generated during the friction process.

Figure 10 is a cross-sectional TEM image of the multilayer coating after corrosion and friction. It can be seen that the multilayer coating has almost no wear, and a passivation film is formed on the surface of the coating, which is generated by the metal Zr layer next to the ZrN layer. It can be seen that part of the metal Zr layer is "consumed" because the corrosion solution penetrates into the metal Zr through gaps or cracks in the top layer of ZrN. The anodic dissolution of the Zr metal layer destroys the integrity of the coating, but at the same time, the generated ZrO ₂ will form a passivation film on the coating surface, which blocks the coating from contacting with the corrosive solution and improves its corrosion resistance. When ZrO2 participates in the friction process, it also plays a certain role in lubrication, so the multi _- layer coating has a lower wear rate and friction coefficient.

In the multi-layer system, the presence of the metal layer can reduce the corrosion of the nitride layer, and the hard nitride layer provides strong support for friction, and the two cooperate with each other. Due to the increased transverse interface, cracks can selectively grow horizontally under loading stress catalysis. The corrosive medium is blocked on the Zr/ZrN interlayer surface, and the anodic dissolution of the Zr metal layer causes cracks on the interlayer surface to expand. With the intensification of corrosion and continuous reciprocating mechanical friction, the entire Zr/ZrN layer on the top of the coating falls off. The fresh Zr/ZrN layer was exposed to the corrosive tribological environment to repeat the previous process. This "self-healing" failure behavior delays the time for the corrosive liquid to spread to the substrate, greatly increasing the service life of the titanium alloy, which has very important practical significance for biomedical devices.

The above descriptions are only preferred embodiments of the present invention, and are only illustrative rather than restrictive to the present invention. Those skilled in the art understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, but all will fall within the protection scope of the present invention.

Claims (8)

1. a kind of method by Zr/Zr ₂ N/ZrN multi-layer coating improves the anti-corrosion wear performance of titanium alloy surface, is characterized in that, comprises the following steps: S1, Ultrasonic cleaning and drying of titanium alloy samples; S2, placing the titanium alloy pattern processed in step S1 on the substrate turret, heating and vacuuming, introducing argon gas, opening the Ti target, performing ion bombardment on the surface of the substrate, and cleaning the surface of the substrate by ion etching, Simultaneously activate the substrate; S3, after the ion etching in step S2 is completed, keep the deposition temperature and the pressure of the furnace chamber constant, open the Zr target, and deposit the metal Zr layer; S4, after the deposition of the Zr metal layer in step S3 is completed, keep the deposition temperature constant, turn off the argon gas, inject nitrogen gas, and deposit the Zr ₂ N transition layer; S5, after the deposition of the Zr ₂ N transition layer in step S4 is completed, keep the deposition temperature constant, continue to feed nitrogen gas, and deposit the ZrN layer; S6, repeating steps S3-S5, alternately depositing Zr metal layer, Zr ₂ N transition layer and ZrN layer to obtain a titanium alloy with Zr/Zr ₂ N/ZrN multi-layer coating deposited on the surface. 2. a kind of method as claimed in claim 1 through Zr/Zr ₂ N/ZrN multi-layer coating improves the corrosion and wear resistance performance of titanium alloy surface, it is characterized in that, in the described step S2, the argon gas flow rate is 200～600sccm , the negative bias voltage of the substrate is -200V, and the ion etching time is 40min. 3. a kind of method as claimed in claim 1 by Zr/Zr ₂ N/ZrN multilayer coating improves the corrosion and wear resistance performance of titanium alloy surface, it is characterized in that, in described step S3, substrate bias is-60 ～-80V, the target current of the metal Zr target is 100～130A, and the deposition time is 5～10min. 4. a kind of method as claimed in claim 1 by Zr/Zr ₂ N/ZrN multilayer coating improves titanium alloy surface corrosion and wear resistance, it is characterized in that, the pressure after feeding nitrogen in the described step S4 is 1-2Pa, the flow rate of nitrogen gas is 100-300sccm, and the deposition time is 2-4min. 5. a kind of method as claimed in claim 1 by Zr/Zr ₂ N/ZrN multilayer coating improves titanium alloy surface corrosion and wear resistance, it is characterized in that, in described step S5, continue to pass into nitrogen pressure after being 2～5Pa, N ₂ flow rate is 400～800sccm, deposition time is 10～15min. 6. a kind of method as claimed in claim 1 by Zr/Zr ₂ N/ZrN multi-layer coating improves titanium alloy surface corrosion and wear resistance, it is characterized in that, in described step S6, deposit Zr metal layer, ZrN alternately The number of ₂ N transition layer and ZrN layer is 7 times. 7. a kind of method as claimed in claim 1 by Zr/Zr ₂ N/ZrN multilayer coating improves titanium alloy surface corrosion and wear resistance, it is characterized in that, Zr/Zr ₂ N/ The ZrN multilayer coating includes a plurality of Zr/Zr ₂ N/ZrN coating units, and the Zr/Zr ₂ N/ZrN coating unit includes a metal Zr layer, a Zr ₂ N transition layer and a ceramic ZrN layer, and the Zr/ The thickness of the Zr ₂ N/ZrN coating unit is 3 μm. 8. a kind of method as claimed in claim 7 by Zr/Zr ₂ N/ZrN multi-layer coating improves titanium alloy surface anti-corrosion wear performance, it is characterized in that, the thickness ratio of described metal Zr layer and ceramic ZrN layer The ratio is 1:3, and the thickness of a single metal Zr layer is 110nm.

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