A preparation method of gadolinium oxide modified TiB2-TiC-GH4169 composite coating

Abstract

A preparation method of gadolinium oxide modified TiB2-TiC-GH4169 composite coating, which relates to the technical field of laser surface strengthening. Method: Load Ti powder, B4C powder, GH4169 alloy powder and nano-Gd2O3 powder into a planetary ball mill, dry after ball milling to obtain a mixed powder; adopt the coaxial powder feeding laser cladding method, and use argon as the powder feeding gas and protective gas to in-situ generate the mixed powder on the surface of the preheated H13 steel substrate to obtain a gadolinium oxide modified TiB2-TiC-GH4169 composite coating. The present invention can obtain a preparation method of a gadolinium oxide modified TiB2-TiC-GH4169 composite coating.

Description

Technical Field

[0001] The invention relates to the technical field of laser surface strengthening, and in particular to a method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating. Background Art

[0002] GH4169 is a nickel-based precipitation-strengthened high-temperature alloy with a long-term service temperature of up to 650°C or above. It has high strength, oxidation resistance, excellent corrosion resistance, fatigue resistance and other properties in high-temperature service environment, and has good welding performance. It is widely used in many high-temperature fields such as aerospace, petrochemical, and nuclear energy. However, due to the low hardness and poor wear resistance of the pure nickel-based high-temperature alloy GH4169 coating, its application in high-temperature wear environment is limited. TiB2 and TiC have a high melting point, excellent hardness and wear resistance, and a relatively low thermal expansion coefficient. They are ideal materials for high-temperature applications. In particular, the high-temperature hardness and wear resistance of the TiB2-TiC composite reinforced coating are better than those of the single TiB2 or TiC reinforced coating. However, in the preparation process of the TiB2-TiC composite reinforced coating, the TiB2 and TiC directly added from the outside often cause the coating to crack due to insufficient wettability with the metal matrix.

[0003] Laser cladding is an effective surface coating manufacturing technology. Under the action of high-energy laser beam, the cladding powder quickly melts and solidifies on the substrate surface. Due to the large temperature gradient, a fine-grained coating will be formed on the substrate surface. Compared with other surface strengthening technologies, it has the advantages of fast processing speed, easy to control coating thickness, small dilution, strong metallurgical bonding between substrate and coating, and small heat-affected zone. It is considered to be a green and environmentally friendly remanufacturing technology. However, laser cladding technology also has shortcomings. The local stress concentration of the coating caused by the faster cooling rate can easily cause cracking of the coating. Summary of the invention

[0004] The purpose of the present invention is to solve the above technical problems and to provide a method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating.

[0005] A method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating is carried out according to the following steps:

[0006] Step S1: Put Ti powder, B4C powder, GH4169 alloy powder and nano Gd2O3 powder into a planetary ball mill, and mill for 2 to 4 hours. After the milling, dry the powder to obtain a mixed powder;

[0007] The mass fraction of GH4169 alloy powder in the mixed powder is 20% to 60%, the mass fraction of nano Gd2O3 powder is 1% to 4%, and the mass ratio of Ti powder to B4C powder is (15 to 21):7;

[0008] Step S2: pretreating the surface of the H13 steel substrate, and then placing it in a vacuum drying oven for preheating to obtain a preheated H13 steel substrate;

[0009] Step S3: coaxial powder feeding laser cladding is adopted, and argon is used as powder feeding gas and protective gas, and the mixed powder obtained in step S1 is in situ self-generated on the surface of the preheated H13 steel substrate obtained in step S2 to obtain a gadolinium oxide modified TiB2-TiC-GH4169 composite coating, the laser power is 1000-1200W, and the laser scanning speed is 180-240mm / min.

[0010] Principle of the present invention:

[0011] Numerous studies have shown that trace amounts of rare earth or its oxides can reduce defects in coatings, inhibit grain growth, improve coating structure, and effectively reduce cracking of coatings, and are widely used in coating surface modification. In-situ synthesis technology is to induce an exothermic chemical reaction through an external heat source, and each component synthesizes a compound in situ. This method can effectively improve the wettability between the ceramic reinforcement phase and the metal matrix, and improve the bonding force between the ceramic reinforcement phase and the metal matrix. In order to maximize the advantages of the above-mentioned material system and preparation method, a complementary formation is formed. Therefore, the present invention selects GH4169 and TiB2-TiC with complementary high temperature performance, hardness and wear resistance as the cladding material system, utilizes the advantages of laser cladding and in-situ synthesis technology, and exerts the modification effect of rare earth oxide nano Gd2O3 on the coating, and successfully prepares a rare earth modified TiB2-TiC-GH4169 composite coating with good molding, uniform structure and excellent high temperature mechanical properties.

[0012] Beneficial effects of the present invention:

[0013] 1. The present invention uses GH4169 high-temperature alloy powder, Ti powder and B4C powder in appropriate proportions and particle sizes as the basic powder system, combined with a composite coating prepared by laser cladding, which not only achieves the effect of in-situ synthesis of TiB2-TiC ceramic reinforcement particles, but also gives full play to the high-temperature performance advantages of G4169 high-temperature alloy, greatly improves the wettability between TiB2-TiC ceramic particles and the matrix, and the composite coating is well formed without obvious cracking, and the high-temperature hardness and wear resistance are significantly improved.

[0014] 2. The present invention utilizes the modification effect of rare earth oxide on the coating, adds nano Gd2O3 powder to modify the TiB2-TiC-GH4169 composite coating, and prepares the gadolinium oxide modified TiB2-TiC-GH4169 composite coating. Nano Gd2O3 can increase the nucleation rate, refine the grains, and help to further improve the toughness of the coating.

[0015] 3. The nano-gadolinium oxide modified TiB2-TiC-GH4169 composite coating of the present invention forms a tightly bound TiB2-TiC structure formed by the nucleation of TiB2 and TiC, and the morphology of TiB2-TiC presents the characteristics of regional differentiated distribution. The TiB2-TiC on the upper part of the coating is short rod-shaped or block-shaped, and is distributed more densely, while the TiB2-TiC on the lower part of the coating is slender and evenly distributed. The effect of this differentiated distribution of TiB2-TiC is similar to the surface carburization of gear steel, which not only ensures the hardness and wear resistance of the upper part of the coating, but also improves the toughness of the middle and lower part of the coating, and can effectively reduce the cracking phenomenon of the coating caused by stress concentration, so that the coating has a certain impact resistance. The nano-Gd2O3 in the coating is distributed at the edge of the TiB2-TiC phase and inside the matrix, as well as inside the TiC phase, which can effectively inhibit the growth of the TiB2-TiC ceramic phase, refine the matrix grains, improve the toughness of the coating, and reduce the cracking of the coating.

[0016] 4. The coating prepared by the present invention has no obvious cracking phenomenon on the surface, dense structure, uniform distribution of TiB2-TiC ceramic phase, and presents regional differentiated distribution morphology characteristics. The room temperature hardness of the coating is higher than 1400HV0.3, the hardness at 700℃ is higher than 1000HV0.3, the high temperature mechanical properties are significantly improved, and the wear rate is lower than 2×10 -5 mm 3 / Nm.

[0017] The invention can obtain a method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The SEM image of the upper part of the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Example 1 is shown;

[0019] Figure 2 The SEM image of the lower part of the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Example 1 is shown;

[0020] Figure 3 A BSE diagram showing the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Example 1;

[0021] Figure 4 express Figure 3 Spectrum Figure 1 ;

[0022] Figure 5 express Figure 3 Spectrum Figure 2 ;

[0023] Figure 6 express Figure 3 Spectrum Figure 3 ;

[0024] Figure 7 express Figure 3 Spectrum Figure 4 ;

[0025] Figure 8 A microhardness distribution diagram of the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Example 1;

[0026] Fig. 9 A graph showing the high temperature (700°C) wear rate of the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Examples 1-3. DETAILED DESCRIPTION

[0027] Specific implementation method 1: This implementation method is a method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating, which is carried out according to the following steps:

[0028] Step S1: Put Ti powder, B4C powder, GH4169 alloy powder and nano Gd2O3 powder into a planetary ball mill, and mill for 2 to 4 hours. After the milling, dry the powder to obtain a mixed powder;

[0029] The mass fraction of GH4169 alloy powder in the mixed powder is 20% to 60%, the mass fraction of nano Gd2O3 powder is 1% to 4%, and the mass ratio of Ti powder to B4C powder is (15 to 21):7;

[0030] Step S2: pretreating the surface of the H13 steel substrate, and then placing it in a vacuum drying oven for preheating to obtain a preheated H13 steel substrate;

[0031] Step S3: coaxial powder feeding laser cladding is adopted, and argon is used as powder feeding gas and protective gas, and the mixed powder obtained in step S1 is in situ self-generated on the surface of the preheated H13 steel substrate obtained in step S2 to obtain a gadolinium oxide modified TiB2-TiC-GH4169 composite coating, the laser power is 1000-1200W, and the laser scanning speed is 180-240mm / min.

[0032] Beneficial effects of this embodiment:

[0033] 1. This embodiment uses GH4169 high-temperature alloy powder, Ti powder and B4C powder with appropriate proportions and particle sizes as the basic powder system, combined with a composite coating prepared by laser cladding, which not only achieves the effect of in-situ synthesis of TiB2-TiC ceramic reinforcement particles, but also gives full play to the high-temperature performance advantages of G4169 high-temperature alloy, greatly improves the wettability between TiB2-TiC ceramic particles and the matrix, and the composite coating is well formed without obvious cracking, and the high-temperature hardness and wear resistance are significantly improved.

[0034] 2. This embodiment utilizes the modification effect of rare earth oxides on the coating, adds nano Gd2O3 powder to modify the TiB2-TiC-GH4169 composite coating, and prepares a gadolinium oxide modified TiB2-TiC-GH4169 composite coating. Nano Gd2O3 can increase the nucleation rate and refine the grains, which is beneficial to further improve the strength and toughness of the coating.

[0035] 3. In the nano-gadolinium oxide modified TiB2-TiC-GH4169 composite coating of this embodiment, TiB2 and TiC are attached to form a tightly bound TiB2-TiC structure, and the morphology of TiB2-TiC shows the characteristics of regional differentiated distribution. The TiB2-TiC on the upper part of the coating is short rod-shaped or block-shaped, and is densely distributed, while the TiB2-TiC on the lower part of the coating is slender and evenly distributed. The effect of this differentiated distribution of TiB2-TiC is similar to the surface carburization of gear steel, which not only ensures the hardness and wear resistance of the upper part of the coating, but also improves the toughness of the middle and lower parts of the coating, which can effectively reduce the cracking phenomenon of the coating caused by stress concentration, and make the coating have a certain impact resistance. The nano-Gd2O3 in the coating is distributed at the edge of the TiB2-TiC phase and inside the matrix, as well as inside the TiC phase, which can effectively inhibit the growth of the TiB2-TiC ceramic phase, refine the matrix grains, improve the strength and toughness of the coating, and reduce the cracking of the coating.

[0036] 4. The coating prepared in this embodiment has no obvious cracking phenomenon on the surface, dense structure, uniform distribution of TiB2-TiC ceramic phase, and presents regional differentiated distribution morphology. The room temperature hardness of the coating is higher than 1400HV0.3, the hardness at 700℃ is higher than 1000HV0.3, the high temperature mechanical properties are significantly improved, and the wear rate is lower than 2×10 -5 mm 3 / Nm.

[0037] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that the particle size of the nano Gd2O3 powder in step S1 is less than 100 nm.

[0038] The other steps are the same as those in the first specific implementation.

[0039] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that: the rotation speed of the planetary ball mill in step S1 is 200-400 r / min.

[0040] The other steps are the same as those in the first or second embodiment.

[0041] Specific implementation method 4: The difference between this implementation method and specific implementation methods 1 to 3 is that the ball-to-material ratio of ball milling in step S1 is (1-3):1.

[0042] The other steps are the same as those in Specific Embodiments 1 to 3.

[0043] Specific embodiment 5: The difference between this embodiment and specific embodiments 1 to 4 is that the drying temperature in step S1 is 100-120° C. and the drying time is 1-2 hours.

[0044] The other steps are the same as those in Specific Embodiments 1 to 4.

[0045] Specific implementation method 6: The difference between this implementation method and specific implementation methods 1 to 5 is that: in step S2, the surface of the H13 steel substrate is pretreated: the surface of the H13 steel substrate is first polished, and then ultrasonically cleaned using anhydrous ethanol or acetone.

[0046] The other steps are the same as those in Specific Embodiments 1 to 5.

[0047] Specific embodiment 7: The difference between this embodiment and specific embodiments 1 to 6 is that the preheating temperature in step S2 is 150-200° C. and the preheating time is 1-2 hours.

[0048] The other steps are the same as those in Specific Embodiments 1 to 6.

[0049] Specific embodiment eight: The difference between this embodiment and specific embodiments one to seven is that the specific parameters of the coaxial powder feeding laser cladding in step S3 are as follows: the laser beam spot diameter is 3 mm, and the powder feeding speed is 0.8-1.6 r / min.

[0050] The other steps are the same as those in Specific Embodiments 1 to 7.

[0051] Specific embodiment 9: The difference between this embodiment and specific embodiments 1 to 8 is that the flow rate of the powder feeding gas in step S3 is 8 to 15 L / min.

[0052] The other steps are the same as those in Specific Embodiments 1 to 8.

[0053] Specific embodiment 10: The difference between this embodiment and specific embodiments 1 to 9 is that the flow rate of the protective gas in step S3 is 16 to 24 L / min.

[0054] The other steps are the same as those in Specific Embodiments 1 to 9.

[0055] The following examples are used to verify the beneficial effects of the present invention:

[0056] Example 1: A method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating, comprising the following steps:

[0057] Step S1: Ti powder, B4C powder, GH4169 alloy powder and nano Gd2O3 powder are loaded into a planetary ball mill, and ball milled at a speed of 300 r / min for 2 h, with a ball-to-material ratio of 2:1; after the ball milling, dry at a temperature of 100° C. for 2 h to obtain a mixed powder for standby use;

[0058] The mass fraction of GH4169 alloy powder in the mixed powder is 40%, the mass fraction of nano Gd2O3 powder is 2%, and the mass ratio of Ti powder to B4C powder is 18:7; the particle size of the nano Gd2O3 powder is less than 100nm;

[0059] Step S2: pretreating the surface of the H13 steel substrate, and then preheating it in a vacuum drying oven at 200° C. for 1 h to obtain a preheated H13 steel substrate;

[0060] The steps of pre-treating the surface of the H13 steel substrate are as follows: first, the surface of the H13 steel substrate is polished with sandpaper, and then ultrasonically cleaned with anhydrous ethanol;

[0061] Step S3: coaxial powder feeding laser cladding is adopted, and argon is used as powder feeding gas and shielding gas, and the mixed powder obtained in step S1 is in situ formed on the surface of the preheated H13 steel substrate obtained in step S2 to obtain a gadolinium oxide modified TiB2-TiC-GH4169 composite coating.

[0062] The specific parameters of coaxial powder feeding laser cladding are as follows: the laser beam spot diameter is 3mm, the laser power is 1000W, the laser scanning speed is 180mm / min, the powder feeding speed is 1.2r / min; the flow rate of powder feeding gas is 10L / min, and the flow rate of shielding gas is 20L / min.

[0063] Example 2: A method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating, comprising the following steps:

[0064] Step S1: Ti powder, B4C powder, GH4169 alloy powder and nano Gd2O3 powder are loaded into a planetary ball mill, and ball milled at a speed of 300 r / min for 2 h, with a ball-to-material ratio of 2:1; after the ball milling, dry at a temperature of 100° C. for 2 h to obtain a mixed powder for standby use;

[0065] The mass fraction of GH4169 alloy powder in the mixed powder is 40%, the mass fraction of nano Gd2O3 powder is 3%, and the mass ratio of Ti powder to B4C powder is 18:7; the particle size of the nano Gd2O3 powder is less than 100nm;

[0066] Step S2: pretreating the surface of the H13 steel substrate, and then preheating it in a vacuum drying oven at 200° C. for 1 h to obtain a preheated H13 steel substrate;

[0067] The steps of pre-treating the surface of the H13 steel substrate are as follows: first, the surface of the H13 steel substrate is polished with sandpaper, and then ultrasonically cleaned with anhydrous ethanol;

[0068] Step S3: coaxial powder feeding laser cladding is adopted, and argon is used as powder feeding gas and shielding gas, and the mixed powder obtained in step S1 is in situ formed on the surface of the preheated H13 steel substrate obtained in step S2 to obtain a gadolinium oxide modified TiB2-TiC-GH4169 composite coating.

[0069] The specific parameters of coaxial powder feeding laser cladding are as follows: the laser beam spot diameter is 3mm, the laser power is 1000W, the laser scanning speed is 180mm / min, the powder feeding speed is 1.2r / min; the flow rate of powder feeding gas is 10L / min, and the flow rate of shielding gas is 20L / min.

[0070] Example 3: A method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating, comprising the following steps:

[0071] Step S1: Ti powder, B4C powder, GH4169 alloy powder and nano Gd2O3 powder are loaded into a planetary ball mill, and ball milled at a speed of 300 r / min for 2 h, with a ball-to-material ratio of 2:1; after the ball milling, dry at a temperature of 100° C. for 2 h to obtain a mixed powder for standby use;

[0072] The mass fraction of GH4169 alloy powder in the mixed powder is 40%, the mass fraction of nano Gd2O3 powder is 1%, and the mass ratio of Ti powder to B4C powder is 18:7; the particle size of the nano Gd2O3 powder is less than 100nm;

[0073] Step S2: pretreating the surface of the H13 steel substrate, and then preheating it in a vacuum drying oven at 200° C. for 1 h to obtain a preheated H13 steel substrate;

[0074] The steps of pre-treating the surface of the H13 steel substrate are as follows: first, the surface of the H13 steel substrate is polished with sandpaper, and then ultrasonically cleaned with anhydrous ethanol;

[0075] Step S3: coaxial powder feeding laser cladding is adopted, and argon is used as powder feeding gas and shielding gas, and the mixed powder obtained in step S1 is in situ formed on the surface of the preheated H13 steel substrate obtained in step S2 to obtain a gadolinium oxide modified TiB2-TiC-GH4169 composite coating.

[0076] The specific parameters of coaxial powder feeding laser cladding are as follows: the laser beam spot diameter is 3mm, the laser power is 1000W, the laser scanning speed is 180mm / min, the powder feeding speed is 1.2r / min; the flow rate of powder feeding gas is 10L / min, and the flow rate of shielding gas is 20L / min.

[0077] Example 4: A method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating is carried out according to the following steps:

[0078] Step S1: Ti powder, B4C powder, GH4169 alloy powder and nano Gd2O3 powder are loaded into a planetary ball mill, and ball milled at a speed of 300 r / min for 2 h, with a ball-to-material ratio of 2:1; after the ball milling, dry at a temperature of 100° C. for 2 h to obtain a mixed powder for standby use;

[0079] The mass fraction of GH4169 alloy powder in the mixed powder is 40%, the mass fraction of nano Gd2O3 powder is 2%, and the mass ratio of Ti powder to B4C powder is 18:7; the particle size of the nano Gd2O3 powder is less than 100nm;

[0080] Step S2: pretreating the surface of the H13 steel substrate, and then preheating it in a vacuum drying oven at 200° C. for 1 h to obtain a preheated H13 steel substrate;

[0081] The steps of pre-treating the surface of the H13 steel substrate are as follows: first, the surface of the H13 steel substrate is polished with sandpaper, and then ultrasonically cleaned with anhydrous ethanol;

[0082] Step S3: coaxial powder feeding laser cladding is adopted, and argon is used as powder feeding gas and shielding gas, and the mixed powder obtained in step S1 is in situ formed on the surface of the preheated H13 steel substrate obtained in step S2 to obtain a gadolinium oxide modified TiB2-TiC-GH4169 composite coating.

[0083] The specific parameters of coaxial powder feeding laser cladding are as follows: the laser beam spot diameter is 3mm, the laser power is 1200W, the laser scanning speed is 240mm / min, the powder feeding speed is 1.2r / min; the flow rate of powder feeding gas is 10L / min, and the flow rate of shielding gas is 20L / min.

[0084] Figure 1The SEM image of the upper part of the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Example 1 is shown. Figure 2 The SEM image of the lower part of the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Example 1 is shown; Figure 1-2 As shown, it can be seen that there is no obvious cracking phenomenon in the coating. The TiB2 and TiC synthesized in situ in the coating form a tightly bound TiB2-TiC structure by nucleation, and the morphology of TiB2-TiC shows differentiated distribution characteristics. The TiB2-TiC in the upper part of the coating exists in the form of short rods and blocks, and the TiB2-TiC in the middle and lower part of the coating exists in the form of long strips, which are evenly distributed. Gd2O3 is mostly distributed inside the matrix phase and at the edge of TiB2-TiC, and some Gd2O3 also forms segregation inside TiC. The moderate laser power of 1000W and the laser scanning speed of 180mm / min provide sufficient energy for the in-situ reaction of Ti and B4C, ensuring the in-situ synthesis of a large amount of TiB2-TiC structure in the coating. At the same time, the mass fraction of 2% nano-Gd2O3 can improve the structure of the coating and refine TiB2-TiC. This refinement effect is more obvious in the upper part of the coating. The TiB2-TiC in the upper and middle and lower parts of the coating presents differentiated distribution characteristics. The role of this differentiated structure is similar to carburizing the surface of the gear. It not only ensures the hardness and wear resistance of the upper part of the coating, but also improves the toughness of the middle and lower parts of the coating. It can effectively reduce the cracking of the coating caused by stress concentration and make the coating have a certain impact resistance.

[0085] Figure 3 The BSE diagram of the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Example 1 is shown; Figure 3 As shown, Figure 4 express Figure 3 Spectrum Figure 1 , Figure 5 express Figure 3 Spectrum Figure 2 , Figure 6 express Figure 3 Spectrum Figure 3 , Figure 7 express Figure 3 Spectrum Figure 4 .like Figure 3-7 As shown, from the spectrum Figure 1 He Pu Figure 2 The element content of the white phase can be determined to be Gd2O3, and the white phase is segregated inside the TiC phase. Figure 3 The element content of the black phase can be determined to be TiB2. Figure 4The element content can confirm that the dark gray phase is TiC, and the light gray phase between TiB2-TiC is the matrix, which can fully prove that the gadolinium oxide-modified TiB2-TiC-GH4169 composite coating is successfully prepared in this embodiment.

[0086] Figure 8 The microhardness distribution diagram of the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Example 1 is shown; Figure 8 As shown in the figure, it can be seen that the room temperature hardness of the coating surface is higher than 1400HV0.3, and the hardness of the coating surface slowly decreases with the increase of temperature. When the temperature reaches 700℃, the hardness of the coating surface is higher than 1000HV0.3, indicating that the high temperature hardness performance of the composite coating is relatively excellent.

[0087] Fig. 9 The high temperature (700°C) wear rate diagram of the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Examples 1-3 is shown; Fig. 9 As shown in the figure, it can be seen that the wear rate of the three composite coatings is significantly lower than that of the substrate. Under the same experimental conditions, the wear rate of the composite coating in Example 1 is only 1 / 36 of that of the H13 steel substrate. With the increase of the mass fraction of Gd2O3 powder, the wear rate of the composite coating shows a trend of first decreasing and then increasing, indicating that there is an optimal value for the addition amount of Gd2O3 powder, and the more the better.

[0088] In summary, the gadolinium oxide modified TiB2-TiC-GH4169 composite coating prepared in Example 1 has no obvious cracking phenomenon, and the TiB2-TiC in the coating is evenly distributed, showing a regional differentiated distribution characteristic of short rods and blocks on the surface and long strips in the middle. The modification effect of nano-Gd2O3, the high temperature performance of GH4169, and the high hardness and wear resistance of TiB2-TiC not only significantly improve the room temperature hardness of the composite coating, but also are very beneficial to improving the high temperature hardness and wear resistance of the coating, but there is an optimal value for the addition amount of nano-Gd2O3 phase.

[0089] Comparative Example 1:

[0090] Tian Luyan, Li Xinmei, Liu Weibin. Effect of CeO2 addition on microstructure and properties of laser cladding TiB2-TiC / Ni composite coating[J]. Materials for Mechanical Engineering, 2023, 47(09):82-86+93.

[0091] In this document, TiB2 and TiC are added directly from outside without nucleation in the coating, which limits the refinement effect of CeO2 on TiB2 and TiC. The directly added TiB2 and TiC have poor wettability with the substrate, and the prepared coating is prone to cracking, which greatly limits the amount of TiB2 and TiC added in the coating. The total amount of the two added in the document is only 12%, and the average room temperature hardness of the coating is lower than 1100HV0.2. The comprehensive performance of the coating is not ideal.

[0092] Comparative Example 2:

[0093] Hou Nan, Wang Jiafeng, Zhang Xinjie. Effect of scanning speed on microstructure and properties of laser cladding TiB2-TiC / Ni composite coating[J]. World Nonferrous Metals, 2016, (13): 69-70.

[0094] The literature uses a method of mixing powder with a mixer and pre-setting powder for laser cladding. Compared with ball milling and coaxial powder feeding laser cladding, the raw material powder is not mixed uniformly, and the powder pre-setting process is complicated and it is difficult to ensure the uniformity of the preset thickness. At the same time, the literature lacks the regulation of the uniform distribution of TiB2 and TiC. Therefore, the structure of the coating prepared in the literature is not uniform enough, the average room temperature hardness of the coating in the literature is lower than 1200HV0.2, and the high temperature hardness and wear resistance of the coating are difficult to guarantee.

[0095] Comparative Example 3:

[0096] Shao Jinzhong, Li Jun, Song Rui, et al. In-situ synthesis of TiB2 / TiC reinforced Ti2Ni / TiNi dual-phase metal compound-based composite coating and preparation method [P]. Shanghai: CN105112907B, 2018-02-02.

[0097] It can be seen that the comparative example adopts a complex pre-coating laser cladding method, which has low efficiency in pre-coating and cannot be pre-coated on the surface of parts with complex shapes, and cannot meet the needs of industrial applications. In addition, there are a certain number of pores and microcracks in the coating prepared in the comparative example, and the amount of in-situ synthesized TiB2 and TiC is small and the distribution is not uniform, resulting in insufficient hardness and wear resistance of the coating. In addition, the in-situ synthesis reaction in the coating relies on the titanium alloy matrix to provide a titanium source, so it is only suitable for titanium alloy surface strengthening and cannot be applied to other metal surfaces.

[0098] The present invention adopts the method of ball milling powder mixing and coaxial powder feeding laser cladding to prepare the coating, which has high production efficiency and is suitable for industrial application needs. Moreover, the TiB2-TiC in the coating is synthesized in situ, and the wettability of TiB2-TiC and the substrate is good. The designed synthesis amount of TiB2-TiC in the coating can reach more than 50%, ensuring that the coating has high comprehensive performance. At the same time, the coating is modified by nano Gd2O3, the distribution of TiB2-TiC is regulated, and the grains of TiB2-TiC and the matrix phase are refined, which effectively improves the structure and performance of the coating. The prepared coating forms a good metallurgical bond with the substrate, has a dense structure, and has no obvious defects such as pores and microcracks. The comprehensive performance of the coating is relatively excellent. Among them, the average room temperature hardness of the coating surface is higher than 1400HV0.3, and the high temperature hardness at 700°C is higher than 1000HV0.3, which is much higher than the level in the above-mentioned comparative example, showing excellent organizational uniformity and high temperature mechanical properties. In addition, the coating prepared by the present invention has a wide range of applicability. In addition to being suitable for surface strengthening of steel substrates, it can also be used for surface strengthening of metals such as titanium alloys and copper alloys.

Claims

1. A method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating, characterized in that The preparation method is carried out according to the following steps: Step S1: Put Ti powder, B4C powder, GH4169 alloy powder and nano Gd2O3 powder into a planetary ball mill, and mill for 2 to 4 hours. After the milling, dry the powder to obtain a mixed powder; The mass fraction of GH4169 alloy powder in the mixed powder is 20% to 60%, the mass fraction of nano Gd2O3 powder is 1% to 4%, and the mass ratio of Ti powder to B4C powder is (15 to 21):7; Step S2: pretreating the surface of the H13 steel substrate, and then placing it in a vacuum drying oven for preheating to obtain a preheated H13 steel substrate; Step S3: coaxial powder feeding laser cladding is adopted, and argon is used as powder feeding gas and protective gas, and the mixed powder obtained in step S1 is in situ self-generated on the surface of the preheated H13 steel substrate obtained in step S2 to obtain a gadolinium oxide modified TiB2-TiC-GH4169 composite coating, the laser power is 1000-1200W, and the laser scanning speed is 180-240mm / min.

2. The method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating according to claim 1, characterized in that The particle size of the nano Gd2O3 powder in step S1 is less than 100 nm.

3. The method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating according to claim 1, characterized in that In step S1, the rotation speed of the planetary ball mill is 200-400 r / min.

4. The method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating according to claim 1 or 3, characterized in that The ball-to-material ratio of ball milling in step S1 is (1-3):

1.

5. The method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating according to claim 1, characterized in that In step S1, the drying temperature is 100-120° C., and the drying time is 1-2 hours.

6. The method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating according to claim 1, characterized in that In step S2, the surface of the H13 steel substrate is pretreated by first grinding the surface of the H13 steel substrate and then ultrasonically cleaning it with anhydrous ethanol or acetone.

7. The method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating according to claim 1, characterized in that The preheating temperature in step S2 is 150-200° C., and the preheating time is 1-2 hours.

8. The method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating according to claim 1, characterized in that The specific parameters of the coaxial powder feeding laser cladding in step S3 are as follows: the laser beam spot diameter is 3 mm, and the powder feeding speed is 0.8-1.6 r / min.

9. The method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating according to claim 1, characterized in that The flow rate of the powder feeding gas in step S3 is 8 to 15 L / min.

10. The method for preparing a gadolinium oxide modified TiB2-TiC-GH4169 composite coating according to claim 1, characterized in that The flow rate of the protective gas in step S3 is 16 to 24 L / min.

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