Titanium alloy air atmosphere heat treatment protective coating and coating process thereof

Abstract

The invention relates to a titanium alloy air atmosphere heat treatment protective coating and a coating process thereof, and belongs to the field of metal heat treatment. The anti-oxidation coating material disclosed by the invention is composed of a coating framework, an organic binder, a solvent carrier, a modifier and a catalyst, and the components of the anti-oxidation coating material are SiO2, Al2O3, CaO, MgO, TiO2, B2O3, HPMC and H2O. The uniform and compact ceramic coating is prepared on the surface of the titanium alloy welding component through the process steps of slurry preparation, spraying, ultrasonic pretreatment, coating heating and curing and the like. The ceramic structure coating formed after laser scanning heating has excellent high temperature resistance, and can provide good structural stability under the temperature condition of 550-850 DEG C. In the heat treatment process of the titanium alloy welding component, the ceramic coating can effectively isolate corrosion of oxygen, hydrogen and other components to titanium alloy, and the purpose that the surface of a material is not oxidized is achieved while the high-temperature heat treatment process under the air atmosphere condition is met.

Description

Technical Field

[0001] The present invention relates to the field of metal heat treatment, in particular to a post-weld heat treatment anti-oxidation treatment method and control technology for titanium alloy welded structural parts, and more particularly to a titanium alloy air atmosphere heat treatment protective coating and a coating process thereof. Background Art

[0002] Titanium alloy bogies are a key technology path for achieving lightweight manufacturing and transitioning to high-quality, high-performance rail vehicles, such as high-speed trains. With the development of new welded titanium alloy frames, heat treatment of welded joints has become crucial for ensuring weld quality. Due to titanium alloy's poor high-temperature oxidation resistance, elements such as hydrogen, carbon, nitrogen, and oxygen react easily during heat treatment, reducing the plasticity and toughness of the welded joints and directly impacting the performance of the welded structure. Consequently, existing steel frame heat treatment processes are unable to meet the post-weld treatment requirements of titanium alloy bogies. Summary of the Invention

[0003] The purpose of the present invention is to provide a titanium alloy air atmosphere heat treatment protective coating and its coating process, which solves the technical problem of the post-weld stress relief treatment process of titanium alloy welded frames, realizes non-oxidation heat treatment of titanium alloy welded joints, and lays a solid welding process manufacturing technology foundation for the engineering application of titanium alloy bogies. The invention satisfies the anti-oxidation protective coating and coating control method of the air atmosphere heat treatment process of titanium alloy welded components. After the spraying is completed, the ultrasonic surface wave cavitation technology is used to homogenize the pre-coating layer, so that the solid particles in the coating are not segregated and are evenly distributed. The ceramic coating formed has low porosity and significant isolation effect on hydrogen and oxygen. In response to the engineering demand for low-cost post-weld heat treatment of titanium alloy rail passenger car frames, non-oxidation heat treatment of titanium alloy welded components under non-vacuum conditions is realized.

[0004] The above-mentioned purpose of the present invention is achieved through the following technical solutions: The protective coating for titanium alloy heat treatment in air atmosphere is composed of a coating skeleton, an organic binder, a solvent carrier, a modifier, and a catalyst. The coating's components are SiO2, Al2O3, CaO, MgO, TiO2, B2O3, HPMC, and H2O. By mass fraction, the SiO2 content is 40-60%, the Al2O3 content is 15-30%, the CaO content is 5-15%, the MgO content is 2-8%, the TiO2 content is 1-5%, the B2O3 content is 0-3%, the HPMC content is 0.5-2%, and the H2O content is 10-20%, totaling 100%.

[0005] Among the various components of the material, SiO2 is the coating skeleton material, providing high-temperature stability and mechanical strength, and forming a silicate glass phase with Al2O3; Al2O3 enhances chemical stability and reacts with SiO2 to form mullite (3Al2O3·2SiO2), which improves bonding strength; CaO is a flux, lowering the sintering temperature and promoting the formation of anorthite (CaAl2Si2O8); MgO inhibits abnormal grain growth, improves thermal stability, and may form magnesia-alumina spinel (MgAl2O4); TiO2 improves wettability and reduces coating porosity; B2O3 is a low-temperature glaze component that lowers the melting temperature; HPMC is an organic binder, improving the slurry's suspension and coating uniformity, and decomposes and volatilizes after curing; H2O acts as a solvent carrier to adjust the slurry's viscosity.

[0006] Another object of the present invention is to provide a coating process for titanium alloy air atmosphere heat treatment protective coating, including slurry preparation, spraying, ultrasonic cavitation treatment and laser sintering process steps, to form a uniform and dense ceramic protective layer on the titanium alloy surface, isolating oxygen during the air atmosphere heat treatment process of titanium alloy welded components, and achieving non-oxidative heat treatment. The steps are as follows: Step 1: Mix the various components of the coating material in proportion to prepare a coating slurry.

[0007] Step 2: Fill the coating slurry into a can and use a spray gun for manual or automatic spraying. During the process, control the distance between the nozzle and the workpiece, the moving speed and the spraying pressure to form a uniform pre-coating layer.

[0008] Step 3: Use ultrasonic surface wave cavitation device to pre-treat the pre-coating layer, so that the solid particles in the coating are separated and the uniformity of each component is improved.

[0009] Step 4: The pre-coating is heated and scanned using a laser. The various components react during the heating process. At low temperatures, the H2O in the pre-coating evaporates, and the HPMC gradually decomposes, forming a porous structure. At intermediate temperatures, alkaline earth metal oxides (CaO) react with SiO2 / Al2O3 to form a eutectic glass phase, filling the pores. At high temperatures, crystalline phases such as mullite (3Al2O3·2SiO2) and anorthite (CaAl2Si2O8) form, densifying the coating. After cooling, a protective layer with excellent insulation properties is formed.

[0010] The beneficial effects of the present invention are as follows: the ceramic structure coating formed by the anti-oxidation coating material of the present invention after laser scanning heating has excellent high-temperature resistance and can provide good structural stability at temperatures of 550°C to 850°C. Ultrasonic surface wave cavitation pretreatment technology can significantly suppress the segregation of solid particles in the pre-coating, improve the uniformity of the coating, and ensure that all components react fully during the coating curing process. The final coating has extremely low porosity and significant anti-oxidation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings described herein are used to provide further understanding of the present invention and constitute a part of this application. The illustrative examples of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0012] Figure 1 This is a schematic diagram of the ultrasonic surface wave cavitation processing principle of the present invention; Figure 2 It is a schematic diagram of the homogenization of the pre-coating layer of the present invention; Figure 3 This is a diagram showing the effect of preparing the anti-oxidation coating of the present invention; Figure 4 The graph shows the comparison results of the surface oxidation energy spectrum of the titanium alloy with and without the anti-oxidation coating after heat treatment according to the present invention. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0014] See also Figures 1 to 4 As shown, the titanium alloy air atmosphere heat treatment protective coating and its coating process of the present invention are aimed at the current engineering demand for low-cost post-weld heat treatment of titanium alloy rail passenger car frames, and realize non-oxidation heat treatment of titanium alloy welded components under non-vacuum conditions. The anti-oxidation coating material of the present invention is composed of a coating skeleton, an organic binder, a solvent carrier, a modifier, and a catalyst. Through the process steps of slurry preparation, spraying, ultrasonic pretreatment, coating heating and curing, and laser sintering, a uniform and dense ceramic coating is prepared on the surface of the titanium alloy welded component. During the heat treatment process of the titanium alloy welded component, the ceramic coating can effectively isolate the corrosion of oxygen, hydrogen and other components on the titanium alloy, and while meeting the high-temperature heat treatment process under air atmosphere conditions, the material surface is non-oxidized, thereby achieving the purpose of non-oxidation heat treatment.

[0015] The anti-oxidation coating material of the present invention is composed of a coating skeleton, an organic binder, a solvent carrier, a modifier, and a catalyst. Its components are: SiO2, Al2O3, CaO, MgO, TiO2, B2O3, HPMC and H2O, and the mass fraction of each component is wt%: (40-60): (15-30): (5-15): (2-8): (1-5): (0-3): (0.5-2): (10-20).

[0016] Among the various components of the material, SiO2 is the main skeleton material, providing high-temperature stability and mechanical strength, and forming a silicate glass phase with Al2O3; Al2O3 can enhance chemical stability and react with SiO2 to form mullite (3Al2O3·2SiO2) to improve bonding strength; CaO is a flux, lowering the sintering temperature and promoting the formation of anorthite (CaAl2Si2O8); MgO’s role is to inhibit abnormal grain growth, improve thermal stability, and may generate magnesium-aluminum spinel (MgAl2O4); TiO2 can improve wettability and reduce coating porosity; B2O3 is a low-temperature glaze component that lowers the melting temperature; HPMC is an organic binder, improving the slurry’s suspension and coating uniformity, and decomposes and volatilizes after curing; H2O is a solvent carrier to adjust the slurry’s viscosity.

[0017] The coating method of the anti-oxidation coating of the present invention comprises the following steps: Step 1: Slurry preparation (1) Dry the oxide powder (SiO2, Al2O3, etc.) to avoid agglomeration and moisture affecting dispersibility; (2) Control the powder particle size by ball milling or air flow milling to improve the slurry suspension stability; (3) Using deionized water as solvent, add anionic dispersant; (4) Add the main components such as SiO2, Al2O3, flux (CaO) and functional additives (TiO2, B2O3) in sequence and stir thoroughly; (5) Pre-dissolve HPMC in warm water and add it slowly to the slurry to avoid agglomeration; (6) The slurry is vacuum-bubbled and allowed to stand at room temperature to allow the components to be fully wetted and reach rheological equilibrium.

[0018] Step 2: Spraying (1) Pretreatment of titanium alloy substrate to remove impurities such as oil; (2) Set the spray gun diameter, air pressure, distance and spray speed to spray evenly without exposing the bottom.

[0019] Step 3: Ultrasonic pretreatment (1) Place the ultrasonic transducer indenter 3, adjust the incident angle of the longitudinal wave, and excite the ultrasonic longitudinal wave; the ultrasonic longitudinal wave excites a surface wave on the surface of the titanium alloy substrate 1, and propagates forward in the bonding area between the titanium alloy substrate 1 and the pre-coating 2.

[0020] (2) Adjust the position of the ultrasonic transducer pressure head and perform multi-point treatment, ensuring sufficient homogenization time for each treatment.

[0021] Step 4: Coating heating and curing (1) Set the laser power and spot diameter parameters; (2) Plan the scanning path and set the scanning speed; (3) Scanning heating, coating curing and molding; (4) Visual inspection: the coating has no cracks, bubbles or deformation. Example

[0022] Step 1: Slurry preparation (1) Dry the oxide powder (SiO2, Al2O3, etc.) at 20°C for 2 hours to avoid agglomeration and moisture affecting dispersibility; (2) Through ball milling, the particle size is controlled to ≤5μm, improving the slurry suspension stability; (3) Deionized water was used as the solvent (accounting for 20%), and 0.5% sodium polyacrylate was added as an anionic dispersant; (4) First add the main components such as SiO2 and Al2O3, then add the flux (CaO) and functional additives (TiO2, B2O3) in sequence, stirring for 15 minutes each step; (5) Predissolve hydroxypropyl methylcellulose (HPMC, 2%) in 60°C warm water and add the slurry slowly to avoid agglomeration; (6) The slurry was treated under vacuum for 20 minutes to eliminate bubbles and then allowed to stand at room temperature for 12 hours to allow the components to be fully wetted and reach rheological equilibrium.

[0023] (7) The proportion of each component: SiO2 accounts for 50%, Al2O3 accounts for 25%, CaO accounts for 10%, MgO accounts for 5%, TiO2 accounts for 3%, B2O3 accounts for 2%, HPMC accounts for 2%, and H2O accounts for the remainder.

[0024] Step 2: Spraying (1) Pretreatment of titanium alloy substrate to remove impurities such as oil; (2) Set the spray gun diameter to 1.0 mm, the air pressure to 0.4 MPa, the distance to 20 cm, and the spray speed to 10 m / min, and spray evenly without exposing the bottom.

[0025] Step 3: Ultrasonic pretreatment (1) Place the ultrasonic transducer head (center frequency: 500 kHz), adjust the longitudinal wave incident angle (second critical angle: 68°), and excite ultrasonic waves; (2) Adjust the position of the ultrasonic transducer head and perform multi-point treatment, ensuring sufficient homogenization time (3 minutes) for each treatment; Step 4: Coating heating and curing (1) Set the laser power to 300W and the spot diameter to 100um; (2) Plan the scanning path and set the scanning speed to 5 mm / s; (3) Scanning heating, coating curing and molding; (4) Visual inspection: the coating has no cracks, bubbles or deformation.

[0026] Under the normal operating conditions described in this example, a uniform, dense ceramic coating can be produced on the surface of the titanium alloy welded component. After a stress relief annealing heat treatment at 550°C for 90 minutes, no significant oxidation was observed in the titanium alloy base metal, weld seam, or other areas, fully meeting the requirements for non-oxidative heat treatment of titanium alloy welded components in air atmosphere.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements to the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A titanium alloy air atmosphere heat treatment protective coating, characterized by: The coating components include a coating skeleton, an organic binder, a solvent carrier, a modifier, and a catalyst.

2. The titanium alloy air atmosphere heat treatment protective coating according to claim 1, characterized in that: The components of the coating are SiO2, Al2O3, CaO, MgO, TiO2, B2O3, HPMC and H2O, among which, by mass fraction, the content of SiO2 is 40~60%, the content of Al2O3 is 15~30%, the content of CaO is 5~15%, the content of MgO is 2~8%, the content of TiO2 is 1~5%, the content of B2O3 is 0~3%, the content of HPMC is 0.5~2%, and the content of H2O is 10~20%, and the total mass fraction is 100%.

3. The titanium alloy air atmosphere heat treatment protective coating according to claim 2, characterized in that: SiO2 is the coating skeleton material, providing high-temperature stability and mechanical strength, and forming a silicate glass phase with Al2O3; Al2O3 enhances chemical stability and reacts with SiO2 to form mullite 3 Al2O3·2 SiO2, which improves bonding strength; CaO is a flux, lowering the sintering temperature and promoting the formation of anorthite CaAl2Si2O8; MgO inhibits abnormal grain growth, improves thermal stability, and may form magnesia-alumina spinel MgAl2O4; TiO2 improves wettability and reduces coating porosity; B2O3 is a low-temperature glaze component that lowers the melting temperature; HPMC is an organic binder, improving the slurry's suspension and coating uniformity, and decomposes and volatilizes after curing; H2O acts as a solvent carrier to adjust the slurry's viscosity.

4. The coating process for titanium alloy air atmosphere heat treatment protective coating according to claim 1, 2 or 3, characterized in that: The method includes slurry preparation, spraying, ultrasonic cavitation treatment and laser sintering process steps, which can generate a uniform and dense ceramic protective layer on the surface of the titanium alloy, isolate oxygen during the air atmosphere heat treatment process of the titanium alloy welded components, and realize oxidation-free heat treatment.

5. The coating process for titanium alloy air atmosphere heat treatment protective coating according to claim 4 is characterized in that: The steps include: Step 1: Mix the components of the coating material in proportion to prepare a coating slurry; Step 2: Fill the coating slurry into a can and spray it manually or automatically with a spray gun. During the process, control the distance between the nozzle and the workpiece, the moving speed and the spraying pressure to form a uniform pre-coating layer. Step 3: Use ultrasonic surface wave cavitation device to pre-treat the pre-coating layer to separate the solid particles in the coating and improve the homogenization of the components; Step 4: Use a laser to heat and scan the pre-coating, and the various components react during the heating process. At low temperatures, H2O in the pre-coating evaporates and HPMC gradually decomposes to form a porous structure. At medium temperatures, alkaline earth metal oxides (CaO) react with SiO2 / Al2O3 to form a eutectic glass phase, filling the pores. At high temperatures, mullite 3Al2O3·2SiO2 and anorthite (CaAl2Si2O8) crystal phases form, densifying the coating. After cooling, a protective layer is formed.

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