RU2764041C1 - Method for increasing wear resistance and anti-corrosion properties of steel products - Google Patents

Abstract

FIELD: materials science.

SUBSTANCE: invention relates to the field of materials science, metal surface treatment and can be used in medicine to increase the wear resistance and anti-corrosion properties of steel products, for example, medical implants. The method for obtaining a wear-resistant anticorrosive coating on an item made of stainless steel grade AISI 316L (03X17N14M3) includes the creation of a Ti-based surface alloy on the item in a single vacuum cycle by alternating the operations of spraying a titanium film by magnetron sputtering and its subsequent liquid-phase mixing with the material of the item using irradiation by a low-energy high-current electron beam (LEHCEB) with a pulse duration of 2-3 mcs, a number of pulses from 3 to 5 and an electron energy density of 2-3 J/cm². A silicon-carbon (α-C:H:SiO_x) finishing coating is then applied to the product.

EFFECT: invention provides a coating that has increased wear resistance and corrosion resistance, having a layer (α-C:H:SiO_x), which has a high biocompatibility with the human biological environment due to the presence of silicon.

5 cl, 2 tbl

Description

The invention relates to the field of materials science, metal surface treatment and can be used in medicine to improve the wear resistance and anti-corrosion properties of steel products, such as medical implants (pumps for mechanical support of the heart, pacemakers, etc.).

At present, to improve the wear resistance and anticorrosion properties of steel products, thin films and coatings are applied, including titanium nitride TiN and diamond-like carbon DLC [1, 2], and surface treatment with concentrated energy flows is also used [3–7].

A known method of high-speed energy exposure using laser remelting of the entire surface of the product [3] or laser remelting of only part of the surface [4], which protects metal products from corrosion.

In addition, it is known that ensuring the transition of steel to a passive state by changing the composition and properties of the surface is the most effective way to reduce corrosion processes. There is a known method [5], in which the surface is subjected to melting using a laser beam and a composition of powders is fed into the melt area. The result is the formation of surface layers with a thickness of 0.2-0.6 mm, which have improved performance properties.

There is a method [6] in which layer-by-layer deposition of powder on the surface of products is carried out, followed by laser irradiation.

The method of synthesizing a surface Ti-Ta-Ni alloy with an amorphous or amorphous-nanocrystalline structure on a substrate of titanium nickelide (TiNi) [7] was chosen closest to the claimed invention in terms of essential common features. In which, as an amorphous film deposited by simultaneous magnetron sputtering of Ti and Ta targets, a film of the composition Ti _60-70 Ta _40-30 (at.%) is used, and subsequent liquid-phase mixing of the film and substrate components and high-speed quenching of the molten surface layer is carried out using a wide-aperture low-energy high-current electron beam (NSEB) with parameters: pulse duration 2÷3 μs, energy density 1.5÷2.5 J/cm ² .

The difference of this technical solution, taken by us as a prototype, is that the technological process was carried out for products made of titanium nickelide, the wear resistance and anticorrosion properties of which were not studied.

The technological problem of the present invention is the development of a method for improving the wear resistance and anti-corrosion properties of stainless steel products.

The technical result of the invention is the creation of a surface alloy based on Ti with a silicon-carbon (α-C:H:SiO _x ) coating deposited on top of a stainless steel grade AISI 316L (03X17H14M3), which has wear-resistant and anti-corrosion properties.

This technical result is achieved by the fact that on a product made of AISI 316L (03X17H14M3) stainless steel, the formation of a surface Ti-stainless steel alloy is carried out in a single vacuum cycle by alternating the operations of deposition of a Ti film and its subsequent liquid-phase mixing with the material of the product. The deposition of titanium films is carried out by the method of magnetron sputtering of a titanium target. Liquid-phase mixing is carried out using a low-energy high-current electron beam with an electron energy density of 2÷3 J/cm ² , a pulse duration of 2-3 μs and a number of pulses of 3-5 times. In a single vacuum cycle, the finishing application of an anti-corrosion and wear-resistant silicon-carbon (α-C:H:SiO _x ) coating is carried out on the product.

In addition, the thickness of the deposited titanium film is adjusted to (0.5÷2.5) µm. In addition, the thickness of the surface alloy Ti-stainless steel is adjusted to (0.5÷5) μm, the number of deposition/irradiation cycles is up to four, depending on the thickness of the deposited Ti film.

Moreover, the article before the first cycle of pre-plating / exposure processing is subjected to low-energy high-current electron beam with an energy density of 4 ÷ 5 J / cm ² and an amount of up to 30 pulses.

In addition, in the proposed method, the finishing silicon-carbon (α-C:H:SiO _x ) coating is applied using a pulsed bipolar bias of the substrate with a negative pulse amplitude from 100 V to 500 V, preferably 300 ± 50 V.

The method is implemented in several stages. AISI 316L (03X17H14M3) stainless steel plates 20×20×2 mm ³ in size were used as a model sample material.

1. Preliminary cleaning of the surface of the samples is carried out in an ultrasonic bath filled first with isopropyl alcohol, then with acetone and distilled water for 10 minutes in each liquid. After that, the samples are dried.

2. Samples are loaded into the vacuum chamber of the “RITM-SP” installation [8], where, in a single vacuum cycle, the NSEP is first pre-treated with an energy density of 4–5 J/cm ² and a number of pulses of 30, in order to clean and homogenize the substrate surface . Then the deposition of a titanium film (thickness 0.5-2.5 μm) by magnetron sputtering of a titanium target (purity 99.95 wt.%) and subsequent irradiation of the surface using NSEB with an electron energy density of 2÷3 J/cm ² , the number of pulses 3- 5 times, pulse duration 2-3 μs. The total number of deposition/irradiation cycles depends on the required thickness of the formed alloy and in our case was up to 4 times (the thickness of the surface alloy is 0.5÷5 µm).

3. Finishing application of anti-corrosion and wear-resistant silicon-carbon (α-C:H:SiO _x ) coating is carried out in a single vacuum cycle with the process of forming a surface alloy based on Ti. The (α-C:H:SiO _x ) coating is applied by the plasma-chemical method in a mixture of argon and polyphenylmethylsiloxane vapor (PFMS-2/5L) at a pressure of 0.1 Pa and a substrate temperature of ~200°C. In this case, the discharge current is 5 ± 1 A, the burning voltage is 140 ± 10 V, and a pulsed bipolar bias voltage with a negative pulse amplitude of 100 to 500 V, a pulse repetition rate of 100 kHz, and a duty cycle of 60% is applied to the substrate holder. The amplitude level of the negative bias voltage pulse affects the change in mechanical and wear-resistant properties due to changes in the content of sp ³ and sp ² hybridized carbon atoms. The optimal value of the amplitude of the negative pulse of the bipolar displacement from the point of view of maximum mechanical and wear-resistant properties is 300±50 V. Study of corrosion resistance.

Corrosion tests were carried out using a P-45X potentiostat-galvanostat (Electrochemical Instruments, Russia) at room temperature 22 ± 2°С in a PBS buffer solution (8 g NaCl, 0.2 g KС1, 1.44 g Na ₂ HPO ₄ , 0.24 g KН _{2 РО 4} ). The circuit operation of the device is based on the involvement of three electrodes: 1. Working electrode - Coated sample (the working section area 0.71 cm ^2); 2. Silver chloride electrode (reference electrode); 3. Graphite rod - counter electrode. Potentiodynamic characteristics were measured in the range from -0.4 V to 2 V with a scan rate of 1 mV/s. Corrosion current density j _corr and polarization resistance R _{p were} determined by the Stern-Giri method [9]. The corrosion rate was evaluated according to the ASTM standard, G102-89(2004) using the formula [10]:

here CR is the corrosion rate (mm/year), coefficient K ₁ =3.27 10 ^-3 (mm⋅g⋅mkA ^-1 ⋅cm ^-1 ⋅year ^-1 ), j _corr is the corrosion current density (mkA⋅cm ^-2 ) , ρ is the density of the material (g⋅cm ^-3 ), and EW is the equivalent weight, for steel AISI 316L (03X17H14M3) is 24.54 (calculated for elements over 1 wt.%).

Study of mechanical properties and wear resistance.

The mechanical properties were determined using a Nanotest 600 nanoindenter (Micro Materials Ltd., GB) with an indenter load of 20 mN. The study of wear resistance was carried out using a tribometer Pin on Disc and Oscillating TRIBOtester (Tribotechnic, France) in ball-disk geometry at a load of 3 N, a travel speed of 25 mm/s and a distance of 1000 m. A VK-8 ball with a diameter of 6 mm was used as a counterbody.

Table 1 presents the results of corrosion tests obtained samples in a solution of PBS (Phosphate buffered saline containing 8 g NaCl, 0.2 g KCl, 1.44 g Na ₂ HPO ₄ , 0.24 g KH ₂ PO ₄ ) at room temperature. The formation of a surface alloy titanium-stainless steel AISI 316L with subsequent deposition of (α-C:H:SiO _x ) film provides a decrease in the corrosion current density j _i from 6.8⋅10 ^-7 A/cm ² (original steel sample No. 1) to 5.5⋅10 ^-10 A/cm ^z (a sample of steel with a formed surface alloy 1 µm thick and a deposited (α-C:H:SiO _x ) film with a thickness of ~2 µm, No. 3) and, accordingly, the corrosion rate CR with 6.9⋅10 ^-3 (No. 1) to 5.7⋅10 ^-6 mm/year (No. 3).

Sample No. 3 also has the maximum polarization resistance R _p 2.5⋅10 ^{9 Ohm⋅cm 2} and one of the minimum corrosion potentials E _corr -22 mV, which, according to the literature data, also characterizes anticorrosion properties. In the case of the formation of a surface alloy with a thickness of 0.5 μm (No. 2) and 5 μm (No. 4) with the same thickness (α-C:H:SiO _x ) of a film with a thickness of ~2 μm, the corrosion current density j _i and the corrosion rate CR increase according to compared with sample no. 3. Thus, there is an optimal thickness of the surface alloy (~1 µm) at which the lowest values of j _i and CR are achieved. Despite this, all samples having a Ti-based surface alloy in combination with an applied α-C:H:SiO _x coating demonstrate anti-corrosion properties.

Table 2 presents the mechanical and wear-resistant properties of the test samples. It can be seen that after the implementation of the proposed method, the mechanical properties of the surface of the product increase significantly, in particular, the hardness H increases by more than 2.5 times, the plasticity index H / E is more than 3.8 times, the resistance to plastic deformation H ³ / E ² more than 36 times. In this case, the samples acquire high wear resistance, the wear rate W decreases from 3.7⋅10 ^-5 to (8÷12) ⋅10 ^{-7 m} m ³ /N⋅m, and the friction coefficient μ from 0.72 to 0.06.

Thus, it has been shown that when implementing this method, which consists in creating a surface alloy of titanium-stainless steel AISI 316L with subsequent application of a (α-C:H:SiO _x ) coating, it is possible to provide high anticorrosion, mechanical and wear-resistant properties of steel products, which is important for medical implants used in aggressive environments.

Sources of information

1. M. Lepicka, M. Gradzka-Dahlke, D. Pieniak, K. Paserbiewicz, A. Niewczas / Effect of me-chanical properties of substrate and coating on wear performance of TiN- or DLC-coated 316LVM stainless steel // Wear . - 2017. - V. 382-383. - P. 62-70.

2. Ying Chen, Xueyuan Nie, Adrian Leyland, Jonathan Housden, Allan Matthew / Substrate and bonding layer effects on performance of DLC and TiN biomedical coatings in Hank's solution under cyclic impact-sliding loads // Surface & Coatings Technology. - 2013. - V. 237. - P. 219-229.

3. Kolotyrkin Ya.M., Yanov L.A., Knyazheva B.M. High-energy methods of surface treatment to protect metals from corrosion // Corrosion and protection against corrosion. Results of science and technology. M.: VNITI AN SSSR, 1986. v.12. pp.185-287.

4. RU 2061100 C1, March 25, 1994

5. RU 2032512 C1, July 29, 1992

6. RU 2443506 C2, 04/05/2010

7. RU 2666950 C1, October 30, 2017

8. A.B. Markov, A.V. Mikov, T.E. Ozur, A.G. Padey. Installation RITM-SP for the formation of surface alloys. Instruments and technique of experiment. 2011. №6. pp. 122-126.

9. D. Batory, A. Jedrzejczak, W. Kaczorowski, L. Kolodziejczyk, B. Burnat, The effect of Si incorporation on the corrosion resistance of aC:H:SiO _x coatings. Diamond & Related Materials, 2016, 67, p. 1-7.

10. ASTM, G102-89(2004), Standard Practice for Calculation of Corrosion Rates and Related Information From Electrochemical Measurements, ASTM International, West Conshohocken, PA, 2004.

Claims (5)

1. A method for obtaining a wear-resistant anti-corrosion coating on a product made of AISI 316L (03X17H14M3) stainless steel, including the creation of a Ti-based surface alloy on the product in a single vacuum cycle by alternating operations of deposition of a titanium film by magnetron sputtering and its subsequent liquid-phase mixing with the material of the product with using irradiation with a low-energy high-current electron beam (LSEB), characterized in that LSEB irradiation is carried out with a pulse duration of 2-3 μs, the number of pulses from 3 to 5 and with an electron energy density of 2-3 J/cm ² , after which a finish is applied to the product silicon-carbon (α-C:H:SiO _x ) coating. 2. The method according to p. 1, characterized in that the thickness of the deposited titanium film is adjusted to 0.5-2.5 microns. 3. Method according to claim 1, characterized in that the thickness of the Ti surface alloy is adjusted to 0.5-5 µm by up to four deposition/irradiation cycles. 4. The method according to p. 1, characterized in that the product is pre-treated before the first deposition / irradiation cycle with NSEP with an energy density of 4-5 J / cm ² with a number of pulses up to 30. 5. The method according to claim 1, characterized in that the anti-corrosion wear-resistant silicon-carbon (α-C:H:SiO _x ) coating is applied when a pulsed bipolar bias voltage is applied to the substrate with a negative pulse amplitude from 100 V to 500 V, preferably 300 ±50 V.