Preparation method of high-hardness (Ti, Cr, V) N composite coating material with multi-layer nanocrystalline structure

Abstract

The invention relates to a preparation method of a high-hardness (Ti, Cr, V) N composite coating material with a multilayer nanocrystalline structure. According to the material, on the basis of a TiVN system, a Cr element is further introduced, controllable lattice distortion is induced by utilizing the size difference between the Cr element and Ti and V, a covalent bond is strengthened by combining 3d electron hybridization of Cr / V, meanwhile, the spreadability of molten drops is optimized by reducing the melting point of the system, and multiple layers of nano columnar crystal structures with different orientations are formed within the thickness of a micron-sized coating. According to the method, the synergistic strengthening of the high intrinsic hardness (1844.80 HV0.5) and the low porosity (4.62%) of the (Ti, Cr, V) N coating is finally achieved, and the method is suitable for the high-load and high-abrasion industrial environment.

Description

Technical Field

[0001] The present invention relates to the field of nano-coating technology, and in particular to a method for preparing a high-hardness (Ti, Cr, V)N multi-component composite coating material with a multi-layer nanocrystalline structure, which is suitable for surface protection of industrial components requiring high wear resistance and high hardness. Background Art

[0002] Ti-based metal nitride coatings are a common surface protective coating. As is well known, TiN is a hard ceramic coating that can be used to improve the surface properties of various alloys, steels, and carbides. With the rapid development of modern industry, higher demands are being placed on material protection. Nitride coatings composed of a single component and structure are no longer sufficient to meet industrial demands, necessitating the development of coatings with superior performance to meet modern industrial conditions. Elements such as Al, Cr, Ta, V, and W can be incorporated into the TiN lattice, significantly enhancing its mechanical properties by altering bonding states and lattice distortion. Reactive plasma spraying is a new, high-efficiency thermal spraying technology that combines plasma spraying with a self-propagating reaction to form a coating. It offers advantages such as high efficiency, low cost, the ability to prepare high-melting-point materials, and controllable coating thickness. Patent CN 110184558B utilizes ball milling and reactive plasma spraying to produce TiVN composite coatings with coating thicknesses of 200-500 μm. However, significant porosity and macrocracks in the coating remain, leaving room for improvement in hardness and overall performance.

[0003] With the development of industry, people have higher demands for coating performance. Nitride coatings composed of a single component and a single structure are no longer able to meet industrial application requirements. Through the multi-element synergistic doping strategy, precise control of the coating microstructure is achieved. The development of a multi-element nitride thick coating with excellent microstructure and high hardness has important engineering application value. Summary of the Invention

[0004] In response to the limitations of current technologies, the present invention proposes a method for preparing a novel high-hardness (Ti, Cr, V) N multi-component composite coating material with a multi-layer nanocrystalline structure. This material further introduces the Cr element on the basis of the TiVN system, utilizes the size difference between the Cr element and Ti and V to induce controllable lattice distortion, combines the 3d electron hybridization of Cr / V to strengthen the covalent bond, and optimizes the spreadability of the molten droplet by lowering the melting point of the system, forming a multi-layer nano-columnar crystal structure with different orientations within the micron-level coating thickness, and ultimately achieving a high intrinsic hardness (1844.80HV) of the (Ti, Cr, V) N coating. 0.5 ) and low porosity (4.62%) are synergistically strengthened and suitable for high-load and high-wear industrial environments.

[0005] The technical solution of the present invention is:

[0006] A method for preparing a high-hardness nano (Ti, Cr, V) N composite coating material having a multilayer nanocrystalline structure, comprising the following steps:

[0007] (1) Material preparation: weigh Ti powder, Cr powder and V powder;

[0008] The proportion of Ti powder is 70-85wt.%, the proportion of Cr powder is 4.4-21.3wt.%, and the proportion of V powder is 8.7-10.6wt.%.

[0009] The purity of Ti powder, Cr powder and V powder is 99.5%, and the particle size is 5-10μm;

[0010] (2) ball milling Ti powder, Cr powder and V powder for 20 to 30 minutes to obtain a mixed powder;

[0011] The ball milling speed is 200-300 rad / min, and the grinding balls are stainless steel grinding balls with diameters of 4-8 mm.

[0012] (3) stirring the mixed raw material powder, sodium carboxymethyl cellulose colloid, sodium tripolyphosphate dispersant and deionized water for 2 to 3 hours to obtain a slurry; feeding the slurry into an atomizer through a peristaltic pump to obtain a reconstructed spherical powder with a particle size of 20 to 50 μm;

[0013] Wherein, 120-180g of sodium carboxymethyl cellulose colloid and 1-5g of sodium tripolyphosphate dispersant are added to every 350-450g of deionized water; the mass of the mixed powder is 30-40wt.% of the slurry;

[0014] The speed of the peristaltic pump is 30-40 rad / min. When the inlet temperature of the spray granulation equipment is 110-120℃;

[0015] (4) The surface of the substrate material is sandblasted, and then a NiCrAlY metal bonding primer layer with a thickness of 80 to 100 μm is sprayed on the sandblasted substrate surface.

[0016] Among them, the powder feeding gas is N2, the flow rate is 0.3-0.5L / min; the working gas is N2, the gas flow rate is 30-50L / min, the power is 35-40kW, and the total spraying time is 2-3min;

[0017] The surface roughness after sandblasting is 3 to 10 μm.

[0018] (5) spraying the Ti-Cr-V composite powder obtained in step (2) onto the surface of the bonding base layer to prepare a (Ti, Cr, V)N composite coating with a thickness of 250 to 350 μm;

[0019] Among them, the powder feeding gas is N2, the flow rate is 0.3-0.5L / min; the working gas is N2, the gas flow rate is 30-50L / min, the power is 35-40kW, and the total spraying time is 2-3min.

[0020] The mass ratio of Ti powder to V powder in step (1) is 8:1.

[0021] The substrate is made of 45# steel, 316L stainless steel or titanium alloy.

[0022] The essential features of the present invention are:

[0023] The present invention selects Cr (bcc) elements, which have a smaller atomic radius than Ti and V elements, similar electronegativity, and the same crystal structure, and introduces them into the TiVN system to prepare a (Ti, Cr, V)N multi-component nitride coating with a multilayer nanocrystalline structure. Compared with the closest technology, this patent has the following improvements: the introduction of Cr elements, whose atomic radius is 0.128nm, and this moderate atomic size difference with Ti (0.147nm) and V (0.134nm) can form controllable lattice distortion in the TiN face-centered cubic (FCC) lattice. At the same time, the 3d electrons of Cr (4.67eV / atom) and the 3d electrons of V (5.25eV / atom) form hybrid orbitals near the Fermi level, which can increase the covalent bond component of the coating through a bond strengthening mechanism, significantly improving the intrinsic hardness. Finally, by adding Cr to lower the melting point of the system, the droplet spreadability was optimized, the grain size of the (Ti, Cr, V) N ceramic phase was controlled (columnar crystal diameter of about 60 to 100 nm, columnar crystal length of about 300 to 600 nm), the coating density was improved, and macroscopic pores and crack defects were reduced. The coating hardness reached as high as 1844.80 HV. 0.5 .

[0024] The beneficial effects of the present invention are:

[0025] (1) Cr (bcc) is selected as an element with a smaller atomic radius, similar electronegativity, and the same crystal structure as Ti and V. The atomic radius of Cr is 0.128 nm. The moderate atomic size difference with Ti (0.147 nm) and V (0.134 nm) can form a controllable lattice distortion in the TiN face-centered cubic (FCC) lattice. At the same time, the synergistic effect of Cr and V can change the electronic structure of the system, form hybrid orbitals near the Fermi level, and increase the covalent bond component of the coating through the bond strengthening mechanism, significantly improving the intrinsic hardness. Finally, the introduction of Cr makes the melting point of the (Ti,Cr,V)N coating lower than that of the TiVN coating. The better molten drop state promotes a closer metallurgical bond between adjacent layers, forming a multi-layer (Ti,Cr,V)N composite coating with a nano-columnar crystal structure in different orientations. The coating has a dense microstructure (4.62%), no macro crack defects, and a coating hardness of up to 1844.80 HV. 0.5 , extending the service life of industrial components.

[0026] (2) Unlike conventional physical and chemical deposition of nitride films (<10 μm), the (Ti, Cr, V)N composite coating prepared by the present invention has a large thickness (>300 μm) and a wider range of applications. Compared to the method of ball milling combined with plasma spraying, the spray powder of the present invention is a quasi-spherical (Ti-Cr-V) composite powder prepared by spray granulation, which increases the powder contact area, improves the self-propagating reaction rate of the spraying, reduces costs, and promotes the mass production of coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the surface XRD pattern of the (Ti, Cr, V) N coating prepared in Example 1; wherein, Figure 1 (a) is the full XRD spectrum, Figure 1 (b) is a comparison chart of the main peak positions;

[0028] Figure 2 is a surface SEM image of the (Ti, Cr, V) N coating prepared in Example 1;

[0029] Figure 3 is a cross-sectional SEM image of the (Ti, Cr, V) N coating prepared in Example 1;

[0030] Figure 4 is a cross-sectional SEM image of the (Ti, Cr, V) N coating prepared in Example 1 after etching;

[0031] Figure 5 is a surface indentation image of the (Ti, Cr, V) N coating prepared in Example 1 under a load of 500 g; DETAILED DESCRIPTION

[0032] Example 1

[0033] Ti powder, Cr powder, and V powder (all with a purity of 99.5%) were weighed and mixed. The particle size of the Ti, Cr, and V powders ranged from 5 to 15 μm. The weight ratio of Ti to V powder was maintained at 8:1, and the Cr content was adjusted to 85 wt.%, 10.6 wt.%, and 4.4 wt.%. The Ti, Cr, and V powders were then milled in a planetary ball mill at 300 rad / min for 20 min using stainless steel balls with diameters of 4 mm, 6 mm, and 8 mm, respectively, in a mass ratio of 1:5:1.

[0034] The obtained mixed raw material powder (300 g), sodium carboxymethyl cellulose colloid (150 g, 1.5 g of sodium carboxymethyl cellulose was added per 100 g of deionized water), sodium tripolyphosphate dispersant (3 g) and deionized water (407 g) were mixed under the action of an electric stirrer for 2 h to uniformly mix the slurry. The solid content of the granular slurry was 35 wt.%. When the inlet temperature of the spray granulation equipment was 120° C., the slurry was fed into an atomizer via a peristaltic pump. The speed of the atomizer high-speed rotating disk was 5000 rpm, and the speed of the peristaltic pump was 30 rad / min. After spray granulation, the slurry was sieved to obtain a reconstructed spherical powder (Ti-Cr-V composite powder) with a particle size of 20 to 50 μm.

[0035] The surface of the 45# steel substrate was sandblasted to a surface roughness of 3μm. A 100μm thick NiCrAlY metal bonding primer was then sprayed onto the sandblasted surface. The powder feed gas was N2 at a flow rate of 0.3L / min, and the working gas was N2 at a flow rate of 40L / min. The power was 35kW, and the total spraying time was 2-3 minutes.

[0036] The Ti-Cr-V composite powder obtained by spray granulation was sprayed onto the surface of the bonding substrate to produce a 350μm thick (Ti,Cr,V)N composite coating. The powder feed gas was N2 at a flow rate of 0.3L / min, and the working gas was N2 at a flow rate of 40L / min. The power was 35kW, and the total spraying time was 2-3 minutes.

[0037] The sprayed samples were subsequently tested for microstructure and microhardness. Phase analysis of the composite coating was performed using a Rigaku Smart Lab X-ray diffractometer, while morphology was observed using a HITACHI S-4800 / TMP cold-field emission scanning electron microscope. The coating was tested using a Shimadzu HMV-2T microhardness tester with a 500g load and 15s loading time.

[0038] The test results of the (Ti, Cr, V) N composite coating are as follows:

[0039] Figure 1 This is the surface XRD pattern of the (Ti,Cr,V)N composite coating prepared in this experiment. TiN, CrN, and VN, formed by the combination of Ti, Cr, and V with N, respectively, all exhibit FCC structures. (Ti,Cr,V)N can be considered a solid solution formed by the interstitial dissolution of these three nitrides. The composite coating primarily comprises (Ti,Cr,V)N, TiO, CrO, and VO phases. Figure 1 (b) gives the comparison of the main peak positions of (Ti,Cr,V)N and TiN, TiCrN2, and TiVN2.

[0040] Figure 2 This is the surface SEM image of the (Ti, Cr, V) N composite coating prepared in this experiment. The coating surface is composed of three (Ti, Cr, V) N phases with different contrasts: dark gray / gray / light gray, corresponding to Ti-rich, V-rich and Cr-rich (Ti, Cr, V) N phases, respectively. The interfaces between the phases are well bonded.

[0041] Figure 3 This is a cross-sectional SEM image of the (Ti, Cr, V)N composite coating prepared in this experiment. The coating exhibits a typical layered structure and has a thickness of 250 to 350 μm. A small amount of pores is present in the coating, and the porosity of the coating cross-section was measured using Image J software and found to be 6.10%.

[0042] Figure 4 The cross-sectional etching SEM image of the (Ti, Cr, V) N composite coating prepared in this experiment shows a lamellar structure of nano-columnar crystals within the micron-level coating thickness. Each layer is composed of nanorods in different orientations. The diameter of the columnar crystal is about 80nm and the length of the columnar crystal is about 300nm.

[0043] Figure 5 The indentation morphology of the (Ti, Cr, V) N composite coating prepared in this experiment under a load of 500g. The obtained indentation was subjected to microhardness analysis, and the average hardness of the indentation morphology of 20 samples in the same group was 1233.05HV. 0.5 , the indentation morphology is regular.

[0044] Example 2

[0045] Ti powder, Cr powder, and V powder were weighed and mixed. During weighing, the weight ratio of Ti powder to V powder was fixed at 8:1, and the Cr powder content was adjusted. Specifically, the Ti powder was 80 wt.%, the V powder was 10 wt.%, and the Cr powder was 10 wt.%. Except for the different ratios of the original powders, the methods and control parameters used were the same as those in Example 1.

[0046] The spray granulated spherical powder and (Ti, Cr, V) N coating prepared by the above method are similar to those in Example 1. Due to the increase in Cr content, there is a slight increase in the light gray area in the coating morphology compared with Example 1. The coating cross-sectional porosity is measured and the coating porosity is 4.62%. The diameter of the columnar crystals between each layer is about 60nm, and the length of the columnar crystals is about 300nm. The average hardness of 20 samples in the same group is 1844.80HV under the indentation morphology. 0.5 , and obtain the optimal ingredient ratio.

[0047] Example 3

[0048] Ti powder, Cr powder, and V powder were weighed and mixed. During weighing, the weight ratio of Ti powder to V powder was fixed at 8:1, and the Cr powder content was adjusted. Specifically, the Ti powder was 75wt.%, the V powder was 9.4wt.%, and the Cr powder was 15.6wt.%. Except for the different ratios of the original powders, the methods and control parameters used were the same as those in Example 1.

[0049] The spray granulated spherical powder prepared by the above method is the same as that in Example 1. The structure of the (Ti, Cr, V) N coating is slightly different from that in Example 1. Due to the increase in Cr content, a diffraction peak of elemental Cr appears in the XRD spectrum of the coating compared with Example 1. The cross-sectional porosity of the coating is measured and the coating porosity is 4.82%. The diameter of the columnar crystals between each layer is about 100 nm, and the length of the columnar crystals is about 400 nm. The average hardness of 20 samples in the same group is 1327.75 HV under the indentation morphology. 0.5 .

[0050] Example 4

[0051] Ti powder, Cr powder, and V powder were weighed and mixed. During weighing, the weight ratio of Ti powder to V powder was fixed at 8:1, and the Cr powder content was adjusted. Specifically, the Ti powder was 70 wt.%, the V powder was 8.7 wt.%, and the Cr powder was 21.3 wt.%. Except for the different ratios of the original powders, the methods and control parameters used were the same as those in Example 1.

[0052] The spray granulated spherical powder and (Ti, Cr, V) N coating prepared by the above method are similar to those in Example 3. Due to the further increase in Cr content, the diffraction peak of elemental Cr in the coating XRD spectrum increases compared with Example 3. The cross-sectional porosity of the coating is measured and the coating porosity is 7.02%. The diameter of the columnar crystals between each layer is about 100 nm, and the length of the columnar crystals is about 400 nm. The average hardness of 20 samples in the same group is 1392.70 HV under the indentation morphology. 0.5 .

[0053] From the above examples, it can be concluded that the present invention introduces Cr into the TiVN system through an in-situ reaction stimulated by a plasma jet, and prepares a (Ti, Cr, V)N composite coating with a thickness of 250 to 350 μm. By controlling the element ratio in the spraying raw material, the diameter of each layer of columnar crystals is about 60 to 100 nm, the length of the columnar crystals is about 300 to 500 nm, and the average microhardness is between 1233.05 and 1844.80 HV. 0.5 High hardness and excellent wear resistance (Ti,Cr,V)N composite coating.

[0054] Matters not covered by the present invention are known technologies.

Claims

1. A method for preparing a high-hardness nano (Ti, Cr, V) N composite coating material with a multilayer nanocrystalline structure, characterized by: The following steps are involved: (1) Material preparation: weigh Ti powder, Cr powder and V powder; The proportion of Ti powder is 70-85wt.%, the proportion of Cr powder is 4.4-21.3wt.%, and the proportion of V powder is 8.7-10.6wt.%; and the mass ratio of Ti powder to V powder is 8:1; (2) ball milling Ti powder, Cr powder and V powder for 20 to 30 minutes to obtain a mixed powder; (3) stirring the mixed raw material powder, sodium carboxymethyl cellulose colloid, sodium tripolyphosphate dispersant and deionized water for 2 to 3 hours to obtain a slurry; feeding the slurry into an atomizer through a peristaltic pump to obtain a reconstructed spherical powder with a particle size of 20 to 50 μm; Wherein, 120-180g of sodium carboxymethyl cellulose colloid and 1-5g of sodium tripolyphosphate dispersant are added to every 350-450g of deionized water; the mass of the mixed powder is 30-40wt.% of the slurry; 1-3g of sodium carboxymethyl cellulose is added to every 100g of deionized water in the sodium carboxymethyl cellulose colloid; Among them, the inlet temperature of the spray granulation equipment is 110-120℃; (4) sandblasting the surface of the substrate material, and then spraying a NiCrAlY metal bonding primer with a thickness of 80 to 100 μm on the sandblasted substrate surface; Among them, the powder feeding gas is N2, the flow rate is 0.3-0.5L / min; the working gas is N2, the gas flow rate is 30-50L / min, the power is 35-40kW, and the total spraying time is 2-3min; (5) spraying the Ti-Cr-V composite powder obtained in step (2) onto the surface of the bonding base layer to prepare a (Ti, Cr, V)N composite coating with a thickness of 250 to 350 μm; Among them, the powder feeding gas is N2, the flow rate is 0.3-0.5L / min; the working gas is N2, the gas flow rate is 30-50L / min, the power is 35-40kW, and the total spraying time is 2-3min.

2. The method for preparing a high-hardness nano (Ti, Cr, V) N composite coating material having a multilayer nanocrystalline structure according to claim 1, wherein: In step (1), the purity of Ti powder, Cr powder and V powder is 99.5%, and the particle size is 5-10 μm.

3. The method for preparing a high-hardness nano (Ti, Cr, V) N composite coating material having a multilayer nanocrystalline structure according to claim 1, wherein: In step (2), the ball milling speed is 200-300 rad / min, and the grinding balls are stainless steel grinding balls with a diameter of 4-8 mm.

4. The method for preparing a high-hardness nano (Ti, Cr, V) N composite coating material having a multilayer nanocrystalline structure according to claim 1, wherein: The rotation speed of the peristaltic pump is 30-40 rad / min.

5. The method for preparing a high-hardness nano (Ti, Cr, V) N composite coating material having a multilayer nanocrystalline structure according to claim 1, wherein: The substrate is made of 45# steel, 316L stainless steel or titanium alloy.

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