Gradient heat-resistant alloy

Abstract

FIELD: powder metallurgy.SUBSTANCE: gradient heat-resistant nickel-based alloy contains, by wt.%: nickel from 56.6 to 59.3, titanium from 3.4 to 4.9, aluminum from 2.1 to 2.9, chromium from 15.3 to 17.9, molybdenum from 5.2 to 8.7, cobalt from 8.8 to 9.9, tungsten from 0.8 to 3.1, carbon from 0.04 to 0.09.EFFECT: graded heat-resistant alloy has increased plasticity with a maximum index of 35.4% and a tensile strength of 1019-1081 MPa.1 cl, 4 dwg, 2 tbl

Description

[0001] The invention relates to the field of powder metallurgy and additive technologies, in particular to a gradient heat-resistant alloy obtained using powders of nickel alloys Rene 41 (R41) and Rene 80 (R80).

[0002] A functionally graded material (FGM) made of nickel-based superalloys with different weldability, namely Rene 41 (R41, weldable) and Rene 80 (R80, non-weldable), obtained by direct laser deposition method is claimed.

[0003] Nickel-based superalloys with a strengthening gamma prime phase are used in single-crystal, directionally solidified, or equiaxed forms. Each crystal contains a gamma phase matrix, which is primarily Ni with elements such as Co, Cr, Mo, W, and Re in solid solution, and gamma prime phase particles, which are primarily Ni3Al with elements such as Ti, Ta, Nb, and V in solid solution. Grain boundaries, if present, are typically filled with carbides and / or borides, which provide cohesive strength. Zr and Hf also contribute to grain boundary adhesion.

[0004] Creep resistance is provided by the elements Mo, W, and Re, which provide solid solution strengthening in the gamma matrix, and Ti, Ta, Nb, and V, which provide solid solution strengthening in the gamma-prime phase particles. Ta has a particularly high strengthening effect on an atomic percentage basis. Similarly, Al provides creep resistance because it increases the amount of gamma-prime particles and because it increases the levels of Mo, W, and Re in the matrix.

[0005] If the concentration of Cr, Mo, W, and Re in the matrix is ​​too high, so-called topologically close-packed (TCP) phases will form during service. Therefore, increased gamma-prime content or elevated levels of Mo, W, or Re should be accompanied by a reduction in Cr if their excessive formation is to be avoided. A disadvantage of TCP phase separation is a reduction in creep strength.

[0006] It is worth noting that many Ni-based superalloys strengthened with significant amounts (>50 vol%) of γ′ particles are considered non-weldable [Welding Metallurgy and Weldability of Nickel-Base Alloys, Wiley Online Books, (n.d.).https: / / onlinelibrary.wiley.com / doi / book / 10.1002 / 9780470500262#aboutBook-pane (accessed August 12, 2025)]. Due to the similarity of welding and AT – both processes involve rapid heating, melting, and subsequent solidification – these alloys might be expected to be problematic for AT. Indeed, numerous studies have found extensive cracking during 3D printing of these Ni-based superalloys [A. Mostafaei, R. Ghiaasiaan, I.-T. Ho, S. Strayer, K.-C. Chang, N. Shamsaei, S. Shao, S. Paul, A.-C. Yeh, S. Tin, A.C. To, Additive manufacturing of nickel-based superalloys: A state-of-the-art review on process-structure-defect-property relationships, Progress in Materials Science 136 (2023) 101108].There are two different approaches to limiting crack formation in nickel-based superalloys. The first involves optimizing process conditions, i.e., laser power, scanning speed, and strategy, which ultimately influences the thermal history of the sample [MC Lam, SCV Lim, H. Song, Y. Zhu, X. Wu, A. Huang, Scanning strategy induced cracking and anisotropic weakening in grain texture of additively manufactured superalloys, Additive Manufacturing 52 (2022) 102660]. Laser power and scanning speed can be combined to obtain integral parameters such as volumetric energy density, and optimal (i.e., producing defect-free samples) processing conditions often refer to medium-energy regimes. Another attractive option is the use of heating (usually induction) to reduce temperature gradients.A second approach to limiting crack formation is the development of new grades of nickel-based superalloys specifically designed for additive manufacturing. Typically, crack formation is associated either with a wide temperature range of (re)crystallization processes or with the precipitation of secondary phases that can cause embrittlement. Computational tools, such as high-performance computing (CALPHAD) [31–34] or machine learning methods, are often used to search for promising compositions [L. Lian, Z. Bao, Q. Xiong, W. Hu, Z. Gao, Y. Zhang, Y. Liu, Intelligent design of crack-resistant nickel-based superalloys for additive manufacturing by machine learning and multilayer filtering strategy, Materials Today Communications 46 (2025) 112387].

[0007] However, the introduction of new grades requires extensive testing of their characteristics. Furthermore, a batch of pre-alloyed powder must be produced and printed under optimal conditions, which have yet to be determined.

[0008] At present, the chemical compositions and methods for producing nickel-based superalloys with a strengthening gamma-prime phase are known.

[0009] The chemical composition of a single-crystal nickel-based superalloy is known [Russian Federation Patent No. RU 2 415 190 C2 "Single-crystal Ni-based superalloy"]. The invention relates to the field of metallurgy, in particular to single-crystal heat-resistant Ni-based alloys. The alloy contains from 5.0 wt.% to 7.0 wt.% Al, from 4.0 wt.% to 10.0 wt.% Ta, from 1.1 wt.% to 4.5 wt.% Mo, from 4.0 wt.% to 10.0 wt.% W, from 3.1 wt.% to 8.0 wt.% Re, from 0.0 wt.% to 2.0 wt.% Hf, from 2.5 wt.% to 8.5 wt.% Cr, from 0.0 wt.% to 9.9 wt.% Co, from 0.0 wt.% to 4.0 wt.% Nb and from 1.0 wt.% to 14.0 wt.% Ru, Ni and inevitable impurities - the rest. The contents of Cr, Hf and Al are preferably set so that the value of the oxidation parameter OP is not less than 108. The alloy is characterized by increased oxidation resistance while maintaining high creep resistance.

[0010] The chemical composition of a nickel-based superalloy with a strengthening gamma-prime phase is known [Russian Federation Patent No. RU 2 450 067 C1 "Nickel-based superalloy with a strengthening gamma-prime phase"]. The invention relates to the field of metallurgy, in particular to a nickel-based superalloy with a strengthening gamma-prime phase, and can be used in hot components such as turbine blades. Claimed is a nickel-based superalloy with a strengthening gamma-prime phase, containing: up to 20 wt.% Co, from 12 to 14 wt.% Cr, from 1 to 2 wt.% Mo, from 1.4 to 2.8 wt.% W, from 5.1 to 5.9 wt.% Al, from 1.1 to 1.6 wt.% Ti, from 3 to 7 wt.% Ta, from 0.01 to 0.3 wt.% C+Zr+B, from 0.05 to 1 wt.% Hf, from 0.05 to 1 wt.% Si and from 0.01 to 0.2 wt.% rare earth elements. The use of the alloy as a hot component of a machine is also declared.The alloy is characterized by high resistance to high-temperature corrosion and oxidation, high compatibility with coatings, phase stability, high creep resistance, and low density. A disadvantage of this method is its insufficient strength at room temperature.

[0011] Rene 80 casting alloy with the following element content in wt.% was selected as the prototype: nickel base, chromium 14.6%, tungsten 3.97%, molybdenum 4.50%, cobalt 8.69%, aluminum 3.01%, titanium 4.94%, carbon 0.17% [Caixiong Yang, Yulai Xu, Heng Nie, Xueshan Xiao, Guoqing Jia, Zhi Shen, Effects of heat treatments on the microstructure and mechanical properties of Rene 80, Materials and Design 43 (2013) 66-73]. This alloy shows an ultimate strength of 1040 MPa with a tensile ductility of 3.18% at room temperature. The disadvantage of this alloy is low ductility at room temperature.

[0012] The objective of the invention is to develop a chemical composition of a gradient material with high plasticity and strength at room temperature.

[0013] The technical result of the invention is to increase the plasticity while maintaining the ultimate strength of the gradient heat-resistant nickel-based alloy at room temperature.

[0014] The technical result is achieved by the proposed chemical composition of the alloy, which was obtained in the course of direct laser growth, containing chemical elements in the weight percentage ratio: nickel from 56.6 to 59.3, titanium from 3.4 to 4.9, aluminum from 2.1 to 2.9, chromium from 15.3 to 17.9, molybdenum from 5.2 to 8.7, cobalt from 8.8 to 9.9, tungsten from 0.8 to 3.1, carbon from 0.04 to 0.09, a distinctive feature of which is that its original chemical composition of high-purity elements ensures the achievement of high mechanical properties at room temperature.

[0015] The novelty and inventive step of the proposed invention lies in the synergistic effect of several factors: the chemical composition of the alloy, the high purity of the claimed elements, and the production method—direct laser deposition. Using the direct laser deposition process, alloy ingots with a high relative density and a defect-free structure were obtained, which undoubtedly has a positive effect on the mechanical properties of the alloy.

[0016] The invention is illustrated by the following materials:

[0017] Fig. 1 - Particle morphology and size distribution of powders (a) R41 and (b) R80.

[0018] Fig. 2 - External appearance (a) and macrostructure (b) of gradient superalloy R41 / P80 produced by direct laser growth.

[0019] Fig. 3 - Microhardness profile of gradient superalloy R41 / P80 depending on the P80 content.

[0020] Fig. 4 - Stress-strain curves (a) and mechanical properties (b) of different layers of gradient superalloy R41 / P80.

[0021] The proposed alloy composition was obtained using a mixture of Rene 41 (R41) and Rene 80 (R80) alloy powders in different concentrations. The powders were obtained by inert gas atomization. The powder particles had a predominantly spherical morphology (Fig. 1). Some particles contain satellites on the surface and spherical pores. The particle size distribution of the powder shows that the particle size is in the range of 40-110 μm. The average particle sizes were ~65 and ~75 μm for R41 and R80, respectively. The chemical composition of the alloy was analyzed by energy-dispersive X-ray spectroscopy (EDS), and the carbon content was analyzed using a METEK-200 analyzer. The actual composition of the powders (in wt.%) is presented in Table 1.

[0022] Table 1 - Chemical composition of powders R41 and R80 (weight %)

[0023] Ni Ti Al Cr Mo Co W Zr Si Fe B C P R41 55.6 2.9 1.8 18.9 9.8 10.3 - - 0.4 0.1 0.010 0.100 0.020 R 80 60.2 5.4 3.2 14.4 4.1 8.5 3.8 0.03 0.2 0.1 0.015 0.028 0.015

[0024] A DED-LB setup based on an LS-3 Yb fiber laser (IPG Photonics, Oxford, MA, USA), an LRM-200iD_7L industrial robot (Fanuc, Oshino-mura, Japan), and an FLW D30 laser welding head (IPG Photonics, Oxford, MA, USA) was used to create an alloy with a smoothly varying composition along the height. Powders were continuously fed into a coaxial four-stream SO12 nozzle via a Metco Twin 150 pneumatic powder feed system (Oerlikon, Freienbach, Switzerland). The growth strategy consisted of gradually increasing the R80 powder concentration in the range from 0% to 100% in 20% increments every 30 mm in the powder mixture. Thus, the alloy sample measuring 16×16×200 mm3 contained six layers with different R41 / R80 powder ratios (Fig. 2). The microstructure of the gradient heat-resistant alloy was studied in the middle of each layer.Primary microstructural characterization was performed on etched (HCl:HNO3 in a ratio of 3:1) surfaces using a Leica Dmi8 optical microscope (Leica Microsystems, Wetzlar, Germany). Detailed microstructural characterization was performed using a Tescan MIRA3 LMH scanning electron microscope (SEM) (Tescan, Brno, Czech Republic) equipped with an Ultim Max 65 energy-dispersive spectroscopy (EDS) detector and a C-Nano electron backscatter diffraction (EBSD) detector (Oxford Instruments NanoAnalysis, Abingdon, UK). EBSD images of 1 × 1 mm2 in size were acquired with a step size of 1 μm. For in-depth analysis, a Thermo Scientific™ Talos F200X G2 S / TEM transmission electron microscope with a 4-segment EDX equipped with an energy-dispersive spectrometer (EDS) detector (FEI Corporation, Hillsboro, OR, USA) was used.Samples for TEM analysis were prepared by standard two-jet electropolishing of mechanically pre-thinned 100 nm foils in a mixture of 90% C4H9OH and 10% HclO4 at 20 V and room temperature. The pore fraction, grain size, and particle size / fraction were quantified using at least five images in the Digimizer (version 6) program. Phase diagrams were calculated using the Thermo-Calc 2022b program with the TC-Python library for automation of calculations in Python. Calculations were performed using the TCHEA4 high-entropy alloys database under equilibrium cooling and nonequilibrium crystallization conditions according to the Gulliver-Scheil model. Vickers microhardness measurements were performed on a Future-Tech FM-310 Vickers microhardness tester (Future-Tech Corp., Kawasaki, Japan) with a load of 300 g (Fig. 3). At least 20 measurements were taken per data point. Tensile tests were performed on an Instron 5882 universal testing machine (Instron, Canton, OH, USA).At least three specimens were obtained. Specimens measuring 12 × 5 × 2 mm3, cut from the middle of each layer in the vertical direction, were tested at room temperature with an initial strain rate of 1×10. −3 With −1 (Fig. 4).

[0025] The implementation of the invention is explained by an example of the process of obtaining a gradient heat-resistant alloy using powders of nickel alloys Rene 41 (R41) and Rene 80 (R80) by the method of direct laser growth in the following examples with different variants of the ratio of their powder fractions, presented in Table No. 2.

[0026] A DED-LB system based on an LS-3 Yb fiber laser, an LRM-200iD_7L industrial robot, and an FLW D30 laser welding head was used to create an alloy with a smoothly varying composition along the height. Powders were fed into a coaxial four-stream SO12 nozzle through a Metco Twin 150 pneumatic powder feed system. The deposition strategy consisted of gradually increasing the R80 powder concentration by 20% every 30 mm in the powder mixture in the range from 0% to 100%. Thus, an alloy sample measuring 16 × 16 × 200 mm 3 contains several layers with different ratios of R41 / R80 powders.

[0027] Table 2 - Concentrations of the main components in different layers of gradient heat-resistant alloy R 41 / R 80, (weight%)

[0028] Layer designation R41 / R80 powder ratio Concentrations of major elements, % Tensile strength, MPa Plasticity, % Ni Ti Al Cr Mo Co W WITH 20% R80 80% / 20% 56.6 3.4 2.1 17.9 8.7 9.9 0.8 0.09 1019 35,4 40% R80 60% / 40% 57.5 3.9 2.4 17.1 7.5 9.5 1.5 0.07 1081 19,1 60% R80 40% / 60% 58.4 4.4 2.6 16.2 6.4 9.2 2.3 0.06 1063 19,7 80% R80 20 % / 80% 59.3 4.9 2.9 15.3 5.2 8.8 3.1 0.04 1057 16,7

[0029] The examples in Table 2 reveal the effect of the concentration of R80 powder in a mixture with R41 powder on the tensile strength and relative elongation of the alloys. The state of the alloy corresponding to the R80 content of 20% was determined - with the distribution of high-purity chemical elements in the weight percentage ratio: nickel 56.6, titanium 3.4, aluminum 2.1, chromium 17.9, molybdenum 8.7, cobalt 9.9, tungsten 0.8, carbon 0.09, possessing the highest ductility of 35.4% at an acceptably high tensile strength of 1019 MPa at room temperature (Fig. 4).

Claims

A graded heat-resistant nickel-based alloy containing titanium, aluminum, chromium, molybdenum, cobalt, tungsten, carbon and nickel, characterized in that it contains components in the following ratio, wt. %: nickel from 56.6 to 59.3; titanium from 3.4 to 4.9; aluminum from 2.1 to 2.9; chromium from 15.3 to 17.9; molybdenum from 5.2 to 8.7; cobalt from 8.8 to 9.9; tungsten from 0.8 to 3.1; carbon from 0.04 to 0.09, Moreover, the alloy has a plasticity of 35.4% and a tensile strength of 1019-1081 MPa.

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