A lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating and its preparation method

Abstract

This invention relates to the field of thermal barrier coating technology for aero-engines, and specifically to a lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating material and its preparation method. The molecular formula of the thermal barrier coating is (La... x Gd y Sm 1‑x‑y The lanthanum-gadolinium-samarium (LGA) ternary medium-entropy thermal barrier coating is prepared by using a lanthanum-gadolinium-samarium (LGA) ternary medium-entropy thermal barrier coating, where x and y = 0.1–0.4; electron beam current intensity of 2.0–2.5 A; sample temperature of 1000–1100 °C; evaporation time of 30–60 min. The evaporation time is controlled to obtain the LGA ternary medium-entropy thermal barrier coating on a rotating sample. The thermal barrier coating material has a thermal expansion coefficient close to that of YSZ and exhibits low thermal conductivity. Furthermore, the use of electron beam physical vapor deposition to prepare the LGA ternary medium-entropy thermal barrier coating will give it a unique columnar crystal structure. Simultaneously, NiCrAlHfTa is prepared using vacuum arc plating equipment as the metal underlayer for the thermal barrier coating, improving the overall compatibility of the coating material. This invention can reduce the thermal conductivity of the coating, increase its service temperature, and improve the problems of insufficient service life and low thermal expansion coefficient.

Description

Technical Field

[0001] This invention belongs to the field of thermal barrier coating technology for aero-engines, and relates to a lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating and its preparation method. Background Technology

[0002] Currently, with the continuous improvement of gas turbine thrust and efficiency, the gas inlet temperature is also increasing. The operating temperature of nickel-based superalloys used in turbine blades and other hot-end components is gradually approaching their operating temperature limits. Thermal barrier coatings (TBCs) are a surface protection technology that utilizes the high-temperature resistance, erosion resistance, corrosion resistance, and low thermal conductivity of ceramic materials. These materials are combined with a metal substrate in the form of a coating to increase the operating temperature of metal components, enhance the high-temperature resistance of hot-end components, extend the service life of hot-end components, and improve engine efficiency.

[0003] Currently, the long-term maximum service temperature of widely used YSZ (6-8 wt.% Y2O3 partially stabilized ZrO2) thermal barrier coating materials cannot exceed 1200℃. During cooling, volume expansion occurs due to the formation of a monoclinic phase, leading to coating failure. The metal binder is a key component in the thermal barrier coating system. It can alleviate the mismatch in thermal expansion coefficients between the ceramic coating and the substrate alloy, and as an intermediate layer between the ceramic surface layer and the substrate alloy, it can improve the thermophysical compatibility of the coating and the substrate alloy. The alloying element composition of the metal binder plays a decisive role in the growth rate, composition, integrity, adhesion to the substrate, and failure behavior of the thermal oxides during service. The prepared metal binder should not form brittle phases and should form good interfacial diffusion resistance with the metal substrate to reduce the degradation of the oxidation resistance of the substrate alloy and the metal binder during service. Among them, MCrAlY metal binders have excellent oxidation resistance, corrosion resistance, and mechanical properties. The most important aspect of coated MCrAlY coatings is the control of alloying elements. The main principle for selecting MCrAIY coating components is to determine whether a protective film with a low growth rate, good adhesion, and continuous density can be formed during high-temperature service. This further improves the bonding strength between the metal binder and the base alloy under thermal cycling conditions and extends the lifespan of the thermal barrier coating. However, the long-term service temperature of thermal barrier coating materials for next-generation high-performance aero-engines must exceed 1200℃. Therefore, researching novel thermal barrier coating materials and metal binder materials and their preparation technologies to further improve the service temperature, oxidation resistance, and bonding strength of thermal barrier coatings has become a key issue in the development of next-generation high-performance aero-engines. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating and its preparation method. The aim is to achieve medium-entropy lanthanum-gadolinium-samarium ternary coating, solving the problems of insufficient service life of single zirconate thermal barrier coatings and the service temperature of YSZ not exceeding 1200℃, thereby reducing the thermal conductivity of the material and increasing its coefficient of thermal expansion. Simultaneously, the use of vacuum arc plating equipment to prepare NiCrAlHfTa as the metal underlayer for the thermal barrier coating further improves the overall compatibility and lifespan of the coating system.

[0005] To solve this technical problem, the technical solution of the present invention is as follows:

[0006] On the one hand, a lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating material is provided, wherein the chemical formula of the lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating material is (La... x Gd y Sm 1-x-y )2Zr2O7, where x, y = 0.1-0.4;

[0007] The molecular formula of the metal substrate of the thermal barrier coating is NiCrAlHfTa; the thickness of the thermal barrier coating is 200-500 micrometers, and the thickness of the metal substrate is 50-150 micrometers; the metal substrate of the thermal barrier coating is prepared by vacuum arc plating technology; the ceramic surface layer of the thermal barrier coating is prepared by evaporation of lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier target material through electron beam physical vapor deposition.

[0008] On the other hand, a method for preparing the thermal barrier coating is provided, the method comprising the following steps:

[0009] Step 1: Mix the raw materials La2O3, Gd2O3, Sm2O3 and ZrO2 according to the material molecular formula ratio, and synthesize lanthanum-gadolinium-samarium ternary medium-entropy target material by high temperature solid-state method at 1900-2000℃.

[0010] Step 2: Prepare NiCrAlHfTa as the metal underlayer for the thermal barrier coating using vacuum arc plating equipment, with a voltage of 600-650V and a current of 15-20A.

[0011] Step 3: The lanthanum-gadolinium-samarium ternary medium-entropy target is loaded into an electron beam physical vapor deposition apparatus. The lanthanum-gadolinium-samarium ternary medium-entropy target is evaporated by electron beam to prepare a lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating on the NiCrAlHfTa substrate. The electron beam current intensity is 2.0-2.5A and the sample temperature is 1000-1050℃.

[0012] The most critical process parameters for electron beam physical vapor deposition in the coating system of this invention are electron beam current and sample temperature. The combination of parameters in this scheme can effectively improve the coating bonding strength.

[0013] The purity of the raw materials La2O3, Gd2O3, Sm2O3, and ZrO2 in the first step of the lanthanum-gadolinium-samarium ternary intermediate entropy model is ≥99%.

[0014] The raw material mixing in step one should be mechanical ball milling for ≥24 hours; the high-temperature solid-state synthesis time should be ≥24 hours.

[0015] In step two, the vacuum degree of the vacuum arc plating equipment is <1×10⁻⁶. -2 Pa; deposition time ≥ 100 min.

[0016] In step three, the vacuum level of the electron beam physical vapor deposition equipment is <5×10⁻⁶. -2 Pa.

[0017] In step three, the evaporation time for the electron beam physical vapor deposition thermal barrier coating is 30-60 minutes.

[0018] In step three, the thermal barrier coating deposited by electron beam physical vapor deposition is cooled to below 200°C in the furnace, and the cooling is natural cooling.

[0019] The beneficial effects of this invention are as follows: As a novel thermal barrier coating material, the lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating exhibits high phase stability after long-term high-temperature heat treatment without phase transformation. Its coefficient of thermal expansion is close to that of YSZ, and it possesses low thermal conductivity and good fracture toughness. Furthermore, the lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating is prepared using electron beam physical vapor deposition (EBPD). Through electron beam current control, the thermal barrier coating will possess a unique columnar crystal structure. Simultaneously, NiCrAlHfTa is prepared as the metal underlayer for the thermal barrier coating using vacuum arc plating equipment. Through current and voltage control, the coating exhibits good thermal cycling performance. Attached Figure Description

[0020] Figure 1 Schematic diagram of thermal conductivity in Example 2

[0021] Figure 2 Schematic diagram of thermal expansion coefficient for Example 2

[0022] Figure 3 Schematic diagram of thermal life in Example 2

[0023] Figure 4 This is a schematic diagram of the columnar crystal structure of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The features of various aspects of the embodiments of the present invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can also be practiced without these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples. The invention is not limited to any specific setups and methods provided below, but covers all improvements, substitutions, etc., to product structures and methods without departing from the spirit of the invention.

[0026] In the various accompanying drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the invention.

[0027] A lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating material, with the molecular formula (La... x Gd y Sm 1-x-y )2Zr2O7, where x, y = 0.1-0.4.

[0028] The preparation method of the lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating material includes the following steps:

[0029] Raw materials La2O3, Gd2O3, Sm2O3, and ZrO2 were mixed according to their molecular formula ratios, with a purity ≥99%. The mixing method was mechanical ball milling for ≥24 hours. Lanthanum-gadolinium-samarium ternary medium-entropy targets were synthesized via a high-temperature solid-state method at 1900-2000℃ for ≥24 hours. NiCrAlHfTa was prepared as the metal underlayer for the thermal barrier coating using vacuum arc plating equipment, with a vacuum degree <1×10⁻⁶. -2 The deposition time is ≥100 min, with a pressure of 600-650 V, a voltage of 600-650 V, a current of 15-20 A, and a deposition time of ≥100 min. The prepared target material is then loaded into an electron beam physical vapor deposition apparatus with a vacuum degree <5 × 10⁻⁶. -2 Pa, electron beam current intensity 2.0-2.5A, evaporation time 30-60min, to prepare thermal barrier coating, and then naturally cool to below 200℃ in the furnace.

[0030] To illustrate (La) x Gdy Sm 1-x-y The effects of Dy and Ce contents in Zr2O7 materials on thermal lifetime were investigated using multiple material synthesis examples, and their Dy and Ce contents are shown in Table 1. It can be seen that, under current rare earth modified coating systems, they exhibit good thermal lifetime.

[0031] Table 1

[0032] Serial Number Chemical formula Thermal life (h) 1 <![CDATA[(La 0.3 Gd 0.3 Sm 0.4 )2Zr2O7]]> 960 2 <![CDATA[(La 0.4 Gd 0.3 Sm 0.3 )2Zr2O7]]> 1050 3 <![CDATA[(La 0.3 Gd 0.4 Sm 0.3 )2Zr2O7]]> 1000 4 <![CDATA[(La 0.2 Gd 0.3 Sm 0.5 )2Zr2O7]]> 700 5 <![CDATA[(La 0.2 Gd 0.5 Sm 0.3 )2Zr2O7]]> 800

[0033] Example 1:

[0034] (1) Raw material ratio: The chemical formula of the lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating material is (La... 0.3 Gd 0.3 Sm 0.4 )2Zr2O7.

[0035] (2) High-temperature solid-state synthesis: The raw materials were mechanically ball-milled for 30 hours, and lanthanum-gadolinium-samarium ternary medium-entropy target material was synthesized by high-temperature solid-state method at 1950℃ for 30 hours;

[0036] (3) Substrate preparation: NiCrAlHfTa was prepared as the metal substrate for the thermal barrier coating using a vacuum arc plating device with a vacuum degree <1×10⁻⁶. -2 Pa, voltage 625V, current 18A, deposition time 150min;

[0037] (4) Thermal barrier coating preparation: A lanthanum-gadolinium-samarium ternary medium-entropy target was loaded into an electron beam physical vapor deposition (EBPD) apparatus. Deposition process parameters: Vacuum degree <5×10⁻⁶ -2 Pa, electron beam current intensity 2.25 A, evaporation time 60 min, after cooling to below 200 degrees Celsius, the deposition equipment was turned on to obtain a lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating.

[0038] The prepared lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating has a thermal conductivity of 0.96 W / (mK) at 1000℃ and a coefficient of thermal expansion of 11.25 × 10⁻⁶. -6 K -1 The bonding strength is 70 MPa; the thermal life is 960 hours.

[0039] Example 2:

[0040] (1) Raw material ratio: The chemical formula of the lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating material is (La... 0.4 Gd 0.3 Sm 0.3 )2Zr2O7.

[0041] (2) High-temperature solid-state synthesis: The raw materials were mechanically ball-milled for 36 hours, and lanthanum-gadolinium-samarium ternary medium-entropy target material was synthesized by high-temperature solid-state method at 2000℃ for 36 hours;

[0042] (3) Substrate preparation: NiCrAlHfTa was prepared as the metal substrate for the thermal barrier coating using a vacuum arc plating device with a vacuum degree <1×10⁻⁶. -2 Pa, voltage 650V, current 20A, deposition time 125min;

[0043] (4) Thermal barrier coating preparation: A lanthanum-gadolinium-samarium ternary medium-entropy target was loaded into an electron beam physical vapor deposition (EBPD) apparatus. Deposition process parameters: Vacuum degree <5×10⁻⁶ -2 Pa, electron beam current intensity 2.15 A, evaporation time 70 min, after cooling to below 200 degrees Celsius, the deposition equipment was turned on to obtain a lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating.

[0044] The prepared lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating has a thermal conductivity of 0.82 W / (mK) at 1000℃ and a coefficient of thermal expansion of 11.45 × 10⁻⁶. -6 K -1 The bonding strength is 65 MPa; the thermal life is 1050 hours.

[0045] like Figure 4 As shown, by controlling the electron beam current and using electron beam physical vapor deposition (EBPD) to prepare a thermal barrier coating, a unique columnar crystal structure is achieved. Simultaneously, NiCrAlHfTa is prepared as the metal underlayer for the thermal barrier coating using vacuum arc plating. By controlling the current and voltage, the overall matching of the coating materials is improved, resulting in better thermal cycling performance. Figure 1 and Figure 2 As shown, in terms of coating design, a uniform coating structure is obtained through entropy reduction in rare earth elements. This invention can both reduce the thermal conductivity of the coating and improve the practical problem of insufficient service life. From Figure 1 It can be seen that the thermal conductivity of the lanthanum-gadolinium-samarium ternary medium-entropy coating at 1000℃ is 0.82 W / (mK), which is 60% lower than that of conventional YSZ. From... Figure 3 It can be seen that the lifetime of the lanthanum-gadolinium-samarium ternary medium-entropy coating is 40% longer than that of conventional YSZ.

Claims

1. A method for preparing a lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating material, characterized in that: The preparation method includes the following steps: Step 1: The raw materials La2O3, Gd2O3, Sm2O3 and ZrO2 are mixed according to the material molecular formula ratio, and lanthanum-gadolinium-samarium ternary medium-entropy target material is synthesized by high temperature solid-state method at 2000℃. Step 2: Prepare NiCrAlHfTa as the metal substrate for the thermal barrier coating using a vacuum arc plating device with a voltage of 650V and a current of 20A; the molecular formula of the metal substrate is NiCrAlHfTa. Thickness: 50~150 micrometers; Step 3: The lanthanum-gadolinium-samarium ternary medium-entropy target is loaded into an electron beam physical vapor deposition apparatus. The lanthanum-gadolinium-samarium ternary medium-entropy target is evaporated by electron beam to prepare a lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating on the NiCrAlHfTa substrate. The electron beam current intensity is 2.15A, the sample temperature is 1000-1050℃, and the thermal barrier coating thickness is 200-500 micrometers. The chemical formula of the lanthanum-gadolinium-samarium ternary medium-entropy thermal barrier coating material is (La... 0.4 Gd 0.3 Sm 0.3 )2Zr2O7; The coating has a thermal conductivity of 0.82 W / (mK) at 1000℃ and a thermal life of 1050 hours.

2. The method according to claim 1, characterized in that: The purity of the raw materials La2O3, Gd2O3, Sm2O3, and ZrO2 in step one is ≥99%.

3. The method according to claim 1, characterized in that: The raw material mixing in step one should be done by mechanical ball milling for a time of ≥24 hours.

4. The method according to claim 1, characterized in that: The synthesis time for step one, the high-temperature solid-state method, is ≥24 hours.

5. The method according to claim 1, characterized in that: In step two, the vacuum degree of the vacuum arc plating equipment is <1×10⁻⁶. -2 Pa.

6. The method according to claim 1, characterized in that: In step two, the deposition time of the vacuum arc plating equipment is ≥100 min.

7. The method according to claim 1, characterized in that: In step three, the vacuum level of the electron beam physical vapor deposition equipment is <5×10⁻⁶. -2 Pa.

8. The method according to claim 1, characterized in that: In step three, the evaporation time of the electron beam physical vapor deposition thermal barrier coating is 30-60 minutes.

9. The method according to claim 1, characterized in that: In step three, the thermal barrier coating deposited by electron beam physical vapor deposition is cooled to below 200°C in the furnace, and the cooling is natural cooling.

Images