Surface strengthening layer for metal materials and preparation method thereof and steel parts

Abstract

The present invention discloses a surface strengthening layer for metal materials, a preparation method thereof and a steel part, and relates to the field of surface treatment technology. The present invention modifies the spraying powder by adding a small amount of titanium oxide, zirconium oxide and rare earth oxide into the aluminum oxide powder. During the high-temperature spraying process, titanium oxide can effectively promote the powder to enter a molten state, reduce the porosity of the coating and refine the grains; during the spraying cooling process, zirconium oxide acts as a nucleation site to promote the growth of fine crystals, and rare earth oxide increases the resistance of grain boundaries to dislocation movement and hinders the movement of grain boundaries. The three toughening bodies promote "synergistic toughening" with each other, and the aluminum oxide coating can achieve a better toughening effect, and the surface plasticity of the coating is enhanced and the deformation resistance is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of surface treatment, in particular to a surface strengthening layer for metal materials and a preparation method thereof and a steel part. Background Art

[0002] Alloy steel is an iron-carbon alloy that is made by adding other alloying elements in addition to iron and carbon. It is an iron-carbon alloy formed by adding an appropriate amount of one or more alloying elements to ordinary carbon steel. Depending on the added elements and the appropriate processing technology, special properties such as high strength, high toughness, wear resistance, corrosion resistance, low temperature resistance, high temperature resistance, and non-magnetic properties can be obtained.

[0003] Alumina coating (Al 2 O 3 ) The coating is widely used in high-temperature, wear-resistant and friction-reducing fields such as aerospace, new energy vehicle manufacturing, rail transportation, and nuclear industry safety protection due to its high hardness, excellent wear resistance, good high-temperature oxidation resistance and corrosion resistance. Due to the high brittleness of the ceramic material itself and the process characteristics of the spraying process itself, the plasma sprayed alumina coating mainly has problems such as low deposition efficiency, high porosity, and a large number of microcracks on the coating surface. During the working process, the expansion and even shedding of microcracks on the surface of the alumina coating due to high temperature and friction is one of the main reasons for the wear and failure of the alumina coating, which seriously affects the service life of the alumina coating and the normal operation of industrial machinery and equipment. Therefore, how to improve the surface microstructure of the alumina coating, eliminate surface microcracks, and improve the wear resistance of the coating is a problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a surface strengthening layer for metal materials and a preparation method thereof and a steel part.

[0005] An embodiment of the present invention provides a surface strengthening layer for a metal material. The raw materials for preparing the surface strengthening layer of the metal material include a main powder and a modifying additive, wherein: the mass proportion of the main powder in the preparation raw material is 78% to 93%, the mass proportion of the modifying additive is 7% to 21%, the main powder is micron alumina, and the modifying additive includes titanium oxide, zirconium oxide and rare earth oxide.

[0006] The present invention also provides a method for preparing a surface strengthening layer, which comprises: providing a substrate, and applying the surface strengthening layer on the surface of the substrate.

[0007] The present invention also provides a steel part used in the fields of marine engineering and automobile manufacturing. The steel part is obtained by applying a surface strengthening layer on the surface of a metal material through the above-mentioned preparation method.

[0008] The present invention has the following beneficial effects:

[0009] The present invention provides a surface strengthening layer for metal materials, a preparation method thereof and a steel part. In the present invention, a small amount of titanium oxide, zirconium oxide and rare earth oxide are added to aluminum oxide powder to modify the spray powder, so that the toughness and strength of the coating can be increased, thereby eliminating surface cracks of the coating, improving the plasticity of the coating, and enhancing the toughness and wear resistance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0011] Figure 1 The SEM images of the surface strengthening layer prepared in Example 1 at different magnifications;

[0012] Figure 2 The SEM images of the surface strengthening layer prepared in Comparative Example 1 at different magnifications;

[0013] Figure 3 The SEM images of the surface strengthening layer prepared in Comparative Example 2 at different magnifications;

[0014] Figure 4 The SEM images of the surface strengthening layer prepared in Comparative Example 3 at different magnifications;

[0015] Figure 5 The SEM images of the surface strengthening layer prepared in Comparative Example 4 at different magnifications;

[0016] Figure 6 The XRD patterns of the powders and surface strengthening layers of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Example 1 are shown;

[0017] Figure 7 The friction coefficient and wear rate variation curves of the surface strengthening layers prepared in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Example 1;

[0018] Figure 8 A bar graph showing the hardness and bonding strength of the surface strengthening layer prepared in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Example 1;

[0019] Fig. 9 This is the EDS spectrum of the surface strengthening layer prepared in Example 1. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0021] The following is a detailed description of a surface strengthening layer for metal materials and a preparation method thereof and a steel part provided in an embodiment of the present invention.

[0022] In a first aspect, an embodiment of the present invention provides a surface strengthening layer for a metal material, wherein the raw materials for preparing the surface strengthening layer of the metal material include a main powder and a modifying additive, wherein: the mass proportion of the main powder in the preparation raw material is 78% to 93%, the mass proportion of the modifying additive is 7% to 21%, the main powder is aluminum oxide, and the modifying additive includes titanium oxide, zirconium oxide and rare earth oxides.

[0023] The embodiment of the present invention provides a surface strengthening layer for metal materials, which is modified by adding a small amount of titanium oxide, zirconium oxide and rare earth oxide to aluminum oxide powder to increase the toughness and strength of the coating so as to eliminate surface cracks of the coating, wherein:

[0024] Alumina powder has excellent thermal stability and is a good thermal spray material, but its toughness is poor and α-Al 2 O 3 Easily converted into γ-Al 2 O 3 phase, resulting in increased coating porosity and a large number of cracks on the surface. Titanium oxide, zirconium oxide and rare earth oxides are added to alumina powder as metal cation oxides and rare earth oxides, which can effectively inhibit the α-Al 2 O 3 Converted to γ-Al 2 O 3 phase, thereby improving the chemical stability of the alumina coating; on the other hand, titanium oxide can promote the growth of alumina grains into short fiber rod-like, plate-like, and long columnar structures, improving the "incompatibility" and "unevenness" problems caused by the "second phase toughening", and ensuring the strength and hardness of the coating while toughening; zirconium oxide can promote the phase change of the alumina coating, consume the energy required for the expansion of the coating crack, relax the stress at the crack tip, hinder the further expansion of the crack, promote the closure of the crack, and improve the fracture toughness and strength of the alumina coating; rare earth oxides are easy to fuse with other elements at high temperatures to generate new phases to hinder the formation of intercrystalline cracks, thereby improving the plasticity of the coating and enhancing the toughness and wear resistance of the coating.

[0025] In some optional embodiments, the mass ratio of aluminum oxide: titanium oxide: zirconium oxide: rare earth oxide is (89-93): (3-5): (3-5): (1-2).

[0026] In some optional embodiments, the titanium oxide includes at least one of anatase titanium oxide and rutile titanium oxide, the zirconium oxide includes at least one of monoclinic zirconium oxide, tetragonal zirconium oxide and cubic zirconium oxide, and the rare earth oxide includes at least one of lanthanum oxide, cerium oxide, praseodymium oxide and rubidium oxide.

[0027] In some optional embodiments, the particle size of aluminum oxide is 20 μm to 55 μm, the particle size of titanium oxide is 15 μm to 45 μm, the particle size of zirconium oxide is 10 μm to 60 μm, and the particle size of rare earth oxide is 20 μm to 70 μm.

[0028] In some optional embodiments, LaZrO is dispersed in the surface strengthening layer for the metal material. 2 , Y 2 ZrTiO 7 , aluminum oxide, titanium oxide, zirconium oxide and rare earth oxide, the minimum surface crack number N of the surface strengthening layer min ≤10, average friction coefficient is 0.2~0.5, average wear rate is 0.5×10 -5 mm 3 / N·m~0.7×10 -5 mm 3 / N·m, hardness ≥800HV 1 , bonding strength ≥12MPa.

[0029] In a second aspect, an embodiment of the present invention further provides a method for preparing a surface strengthening layer, which comprises: providing a substrate, and applying the above-mentioned surface strengthening layer on the surface of the substrate.

[0030] The embodiment of the present invention also provides a method for preparing a surface strengthening layer, which is to apply the above-mentioned surface strengthening layer on the surface of the substrate. The method for applying the surface strengthening layer can be plasma spraying or plasma cladding. For example, during the high-temperature spraying process, titanium oxide can effectively promote the powder raw material to enter a molten state, reduce the porosity of the coating, and refine the grains; during the cooling process of high-temperature spraying, zirconium oxide acts as a nucleation site to promote the growth of fine crystals, and rare earth oxides increase the resistance of grain boundaries to dislocation movement and hinder the movement of grain boundaries. The three toughening agents promote "synergistic toughening" with each other, and the aluminum oxide coating can achieve a better toughening effect, and the surface plasticity of the coating is enhanced and the deformation resistance is further improved.

[0031] In some optional embodiments, a surface strengthening layer is applied on the surface of the substrate by plasma spraying or plasma cladding, wherein: the spraying power is controlled to be 20KW~50KW, the argon flow rate is 35L / min~50L / min, the hydrogen flow rate is 5L / min~10L / min, the spraying distance is 80mm~110mm, and the powder feeding rate is 18g / min~23g / min.

[0032] In some optional embodiments, the method further includes: sandblasting the substrate surface with No. 20 to No. 46 white corundum to improve the surface roughness of the substrate before spraying, and then preheating at 150°C to 220°C; drying the prepared raw materials at 60°C to 100°C for 30min to 60min.

[0033] In some optional embodiments, the substrate includes any one of: bearing steel, high-strength low-alloy steel, alloy structural steel, ultra-high-strength steel, stainless corrosion-resistant steel, heat-resistant steel, tool steel, and mold steel.

[0034] In a third aspect, an embodiment of the present invention further provides a steel part used in the fields of marine engineering and automobile manufacturing, which is obtained by applying a surface strengthening layer on the surface of a metal material through the above-mentioned preparation method. These fields specifically involve engines, transmissions, etc., to improve the working efficiency, stability and service life of these devices.

[0035] As can be seen from the above, the present invention provides a surface strengthening layer for metal materials, a preparation method thereof, and a steel part. The raw materials for preparing the surface strengthening layer for metal materials include a main powder and a modifying additive, wherein: the main powder is aluminum oxide, and the modifying additive includes titanium oxide, zirconium oxide, and rare earth oxides. The surface strengthening layer can be applied to the surface of the substrate using the above-mentioned preparation raw materials. The method is relatively simple, the original powder of the coating is relatively cheap, the reserves are huge, and the production cost is low, and it is easy to realize actual batch production and large-scale application. The steel parts prepared by the scheme provided in the embodiment of the present invention can be widely used in mechanical equipment in the fields of marine engineering, automobile manufacturing, nuclear power industry, petrochemical industry, etc. Such as commonly used motors, pumps, engines, transmissions, fans, compressors, etc., to improve the working efficiency, stability and service life of these equipment.

[0036] The present invention will be further described below in conjunction with the embodiments.

[0037] The crack calculation formula in the following embodiments and comparative examples is as follows:

[0038] .

[0039] in: Nis the number of cracks; E is Young's modulus (unit: Pa); α is the linear thermal expansion coefficient (unit: 1 / °C); ΔT: temperature change (unit: °C); A and n are constants obtained through experiments.

[0040] Example 1

[0041] (1) Weigh 89% of aluminum oxide powder, 5% of titanium oxide powder and 5% of zirconium oxide powder, and 1% of lanthanum oxide powder, wherein: the particle size distribution of the aluminum oxide powder is between 20 μm and 55 μm, the particle size distribution of the lanthanum oxide powder is between 20 μm and 70 μm, the titanium oxide powder is anatase titanium oxide powder, and the particle size distribution is between 20 μm and 38 μm, and the zirconium oxide powder is monoclinic zirconium oxide powder, and the particle size distribution is between 25 μm and 55 μm. The aluminum oxide powder, anatase titanium oxide powder, monoclinic zirconium oxide powder and lanthanum oxide powder weighed above are mixed to obtain a mixed material, and aluminum oxide ceramic balls with a diameter of 5 mm are added at a mass ratio of aluminum oxide ceramic balls to the mixed material of 1 / 3, and the mixture is put into a ball mill and mixed for 4 hours to obtain an original powder for spraying.

[0042] (2) GCr15 bearing steel was selected as the spraying substrate, and the surface of the substrate was sandblasted for cleaning. The sandblasting pressure was 0.6 MPa and the surface roughness was 3.5 μm. The modified powder was placed in an oven and dried at 75°C for 30 minutes, and then cooled in the oven for use.

[0043] (3) Before spraying, the substrate is preheated at a temperature of 200° C. The coating is sprayed on the surface of the pretreated substrate in step (2) using a 9M plasma spray processing center produced by Oerlikon Metco. The process parameters are as follows: plasma spray power of 42 kW, argon gas flow rate of 45 L / min, hydrogen gas flow rate of 5 L / min, spray distance of 90 mm, powder feeding rate of 20 g / min, and a surface strengthening layer, i.e., a doped and modified dense alumina composite ceramic coating, is obtained. The coating thickness is 300 μm.

[0044] Example 2

[0045] (1) Weigh 88% of aluminum oxide powder, 5% of titanium oxide powder and 5% of zirconium oxide powder, and 2% of lanthanum oxide powder, wherein: the particle size distribution of the aluminum oxide powder is between 20 μm and 55 μm, the particle size distribution of the lanthanum oxide powder is between 20 μm and 70 μm, the titanium oxide powder is anatase titanium oxide powder, and the particle size distribution is between 20 μm and 38 μm, and the zirconium oxide powder is monoclinic zirconium oxide powder, and the particle size distribution is between 25 μm and 55 μm. The aluminum oxide powder, anatase titanium oxide powder, monoclinic zirconium oxide powder and lanthanum oxide powder weighed above are mixed to obtain a mixed material, and aluminum oxide ceramic balls with a diameter of 5 mm are added at a mass ratio of aluminum oxide ceramic balls to the mixed material of 1 / 3, and the mixture is put into a ball mill and mixed for 4 hours to obtain an original powder for spraying.

[0046] (2) GCr15 bearing steel was selected as the spraying substrate, and the surface of the substrate was sandblasted for cleaning. The sandblasting pressure was 0.6 MPa and the surface roughness was 3.5 μm. The modified powder was placed in an oven and dried at 75°C for 30 minutes, and then cooled in the oven for use.

[0047] (3) Before spraying, the substrate is preheated at a temperature of 200°C. The coating is sprayed on the surface of the pretreated substrate in step (2) using a 9M plasma spray processing center produced by Oerlikon Metco. The process parameters are as follows: plasma spray power of 40KW, argon gas flow rate of 45L / min, hydrogen gas flow rate of 5L / min, spray distance of 90mm, and powder feeding rate of 20g / min. The surface strengthening layer, i.e., the doped modified dense alumina ceramic composite coating, is obtained, and the coating thickness is 300μm.

[0048] Comparative Example 1

[0049] The steps are similar to those of Example 1, except that the spraying powder is 99% pure aluminum oxide powder by mass.

[0050] Comparative Example 2

[0051] The steps are similar to those in Example 1, except that the spraying powder is 95% by mass of alumina powder and 5% by mass of anatase titanium oxide powder. The alumina powder and anatase titanium oxide powder weighed above are mixed to obtain a mixed material, and alumina ceramic balls with a diameter of 5 mm are added at a mass ratio of alumina ceramic balls to the mixed material of 1 / 3, and the mixture is put into a ball mill and mixed for 4 hours to obtain the original powder for spraying.

[0052] Comparative Example 3

[0053] The steps are similar to those in Example 1, except that the process parameters selected in the preparation process are as follows: plasma spraying power is 15KW, hydrogen flow rate is 3L / min, spraying distance is 120mm, and powder feeding rate is 10g / min. A doped and modified dense alumina composite ceramic coating is obtained, and the coating thickness is 320μm.

[0054] Comparative Example 4

[0055] The steps are similar to those in Example 1, except that the particle sizes of the alumina powder, anatase titanium oxide powder, monoclinic zirconium oxide powder and lanthanum oxide powder are between 68 μm and 82 μm, between 47 μm and 64 μm, between 65 μm and 71 μm and between 73 μm and 84 μm, respectively. The alumina powder, anatase titanium oxide powder, monoclinic zirconium oxide powder and lanthanum oxide powder weighed above are mixed to obtain a mixed material, and a 5 mm diameter alumina ceramic ball is added at a mass ratio of 1 / 3 to the mixed material, and then the mixture is placed in a ball mill and mixed for 4 hours to obtain the original powder for spraying. The surface strengthening layer, i.e., the doped modified dense alumina composite ceramic coating, is obtained by plasma spraying, and the coating thickness is 320 μm.

[0056] Test Results

[0057] Figure 1-Figure 5 The SEM images of the surface strengthening layers prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 at different magnifications are as follows: Figure 1 It can be seen that the use of the solution provided in the embodiment of the present invention to prepare an aluminum oxide coating on the surface of the bearing steel can inhibit the generation of cracks in the aluminum oxide coating and effectively improve the density of the coating. During the high-temperature spraying process, the molten droplets on the coating surface spread well and the cracks were effectively suppressed. The number of cracks in the surface strengthening layer was tested using Image-ProPlus software. The number of coating cracks in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Example 1 were: N 对比例1 =45, N 对比例2 =23, N 对比例3 =27, N 实施例1 =7.

[0058] Figure 6 XRD spectra of the powders and surface strengthening layers of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Example 1: Figure 2 It can be seen that due to the high temperature during spraying, the coating in Example 1 contains 2 O 3 Phase, γ-Al 2 O 3 phase as well as titanium oxide, zirconium oxide and lanthanum oxide, and also produces LaZrO 2 , Y 2ZrTiO 7 Oxides. The generation of these oxides effectively reduces the influence of residual thermal stress on the performance of the coating and effectively improves the mechanical properties of the coating. In Comparative Example 1, there are a large number of cracks on the surface of the surface strengthening layer, the coating hardness and bonding strength are low, and the friction coefficient and wear rate are high. In the surface strengthening layer in Comparative Example 2, due to the addition of titanium oxide reinforcing phase, the coating cracks are reduced, the coating hardness and bonding strength are greatly improved, and the friction coefficient and wear rate are significantly reduced compared with Comparative Example 1. Cracks appear on the surface of the surface strengthening layer in Comparative Example 3, the coating hardness and bonding strength are significantly reduced compared with Example 1, and the friction coefficient and wear rate are significantly improved. In Comparative Example 4, the particle size of the original sprayed powder is large, the powder is not fully melted during the spraying process, and a large number of unmelted particles are present in the coating. The presence of unmelted particles directly leads to a large number of microscopic cracks in the coating; LaZrO is not generated in the coating 2 , Y 2 ZrTiO 7 The coating hardness, bonding strength, wear resistance and other aspects are significantly lower than those in Example 1.

[0059] Figure 7 The friction coefficient and wear rate change curves of the surface strengthening layers prepared in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Example 1 show that the friction coefficient of the coating in Example 1 after doping is only 0.28, and the wear rate is significantly reduced, indicating that the present invention can not only inhibit the generation of cracks on the coating surface, but also effectively improve the wear resistance of the coating.

[0060] Figure 8 The hardness and bonding strength of the surface strengthening layer prepared in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Example 1 are shown in the figure. It can be seen that in addition to containing α-Al 2 O 3 ,γ-Al 2 O 3 , titanium oxide, zirconium oxide and lanthanum oxide, and also produces LaZrO 2 , Y 2 ZrTiO 7 The coating hardness and bonding strength are significantly improved, with the coating hardness reaching 1010.75HV 1 , the bonding strength is 13.6MPa.

[0061] Fig. 9 This is the EDS spectrum of the surface strengthening layer prepared in Example 1: It can be seen that elements such as Ti and La are distributed relatively evenly in the surface strengthening layer.

[0062] It can be seen from the above experimental results that the present invention adopts plasma spraying or plasma cladding to apply a surface strengthening layer on the substrate surface, which can not only improve the service life of the metal material, but also has a lower processing cost, is suitable for a variety of industrial applications, and has good market prospects and application value.

[0063] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A surface strengthening layer for a metal material, characterized in that: The raw materials for preparing the surface strengthening layer of the metal material are composed of a main powder and a modification additive, wherein: the main powder is aluminum oxide, and the modification additive is composed of titanium oxide, zirconium oxide and rare earth oxide; The particle size of the aluminum oxide is 20 μm to 55 μm, the particle size of the titanium oxide is 15 μm to 45 μm, the particle size of the zirconium oxide is 10 μm to 60 μm, the particle size of the rare earth oxide is 20 μm to 70 μm, and the rare earth oxide is lanthanum oxide; The mass ratio of the aluminum oxide: the titanium oxide: the zirconium oxide: the rare earth oxide is (89-93): (3-5): (3-5): (1-2); The surface strengthening layer for metal materials contains LaZrO2, Y2ZrTiO7, aluminum oxide, titanium oxide, zirconium oxide and rare earth oxide dispersed therein, and the minimum surface crack number N of the surface strengthening layer is min ≤10, average friction coefficient is 0.2~0.5, average wear rate is 0.5×10 -5 mm 3 / N·m~0.7×10 -5 mm 3 / N·m, hardness ≥800HV1, bonding strength ≥12MPa.

2. The surface strengthening layer for metal materials according to claim 1, characterized in that: The titanium oxide includes at least one of anatase titanium oxide and rutile titanium oxide, and the zirconium oxide includes at least one of monoclinic zirconium oxide, tetragonal zirconium oxide and cubic zirconium oxide.

3. A method for preparing a surface strengthening layer for a metal material, characterized in that: It includes: A substrate is provided, and the surface strengthening layer according to any one of claims 1 to 2 is applied on the surface of the substrate.

4. The preparation method according to claim 3, characterized in that: The surface strengthening layer is applied on the surface of the substrate by plasma spraying or plasma cladding, wherein: the spraying power is controlled to be 20KW~50KW, the argon flow rate is 35L / min~50L / min, the hydrogen flow rate is 5L / min~10L / min, the spraying distance is 80mm~110mm, and the powder feeding rate is 18g / min~23g / min.

5. The preparation method according to claim 3, characterized in that: Also includes: Before spraying, the surface of the substrate is sandblasted with No. 20 to No. 46 white corundum to improve the roughness of the surface of the substrate, and then preheated at 150° C. to 220° C.; the prepared raw materials are dried at 60° C. to 100° C., and the drying time is 30 min to 60 min.

6. The preparation method according to claim 3, characterized in that: The substrate is a metal material, and the metal material includes any one of bearing steel, high-strength low-alloy steel, alloy structural steel, ultra-high-strength steel, stainless corrosion-resistant steel, heat-resistant steel, tool steel, and mold steel.

7. A steel part used in marine engineering and automobile manufacturing, characterized in that: The steel part is obtained by applying a surface strengthening layer on the surface of a metal material using the preparation method described in any one of claims 3 to 6.

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