Structure and Properties of Heat-Resistant Alloys NiAl–Cr–Co–X (X = La, Mo, Zr, Ta, Re) and Fabrication of Powders for Additive Manufacturing

Abstract

The NiAl–Cr–Co–X alloys were produced by centrifugal self-propagating high-temperature synthesis (SHS) casting. The effects of dopants X = La, Mo, Zr, Ta, and Re on combustion, as well as the phase composition, structure, and properties of the resulting cast alloys, have been studied. The greatest improvement in overall properties was achieved when the alloys were co-doped with 15% Mo and 1.5% Re. By forming a ductile matrix, molybdenum enhanced strength characteristics up to the values σucs = 1604 ± 80 MPa, σys = 1520 ± 80 MPa, and εpd = 0.79%, while annealing at T = 1250 ℃ and t = 180 min improved strength characteristics to the following level: σucs = 1800 ± 80 MPa, σys = 1670 ± 80 MPa, and εpd = 1.58%. Rhenium modified the structure of the alloy and further improved its properties. The mechanical properties of the NiAl, ZrNi5, Ni0.92Ta0.08, (Al,Ta)Ni3, and Al(Re,Ni)3 phases were determined by nanoindentation. The three-level hierarchical structure of the NiAl–Cr–Co+15%Mo alloy was identified. The optimal plasma treatment regime was identified, and narrow-fraction powders (fraction 8–27 µm) characterized by 95% degree of spheroidization and the content of nanosized fraction <5% were obtained.

The Effect of Dopants on Structure Formation and Properties of Cast SHS Alloys Based on Nickel Monoaluminide

“…Submicron-sized NiAl precipitates were detected inside the interdendritic layers. As demonstrated by Aheiev et al [31], tantalum localization along the boundaries of the major phase grains had a positive effect on strength properties and increased plastic strain at room temperature. Stringed precipitates of α-Cr were also revealed in the NiAl matrix.…”

“…Microdoping with molybdenum and niobium (the base+MoNb alloy) obtained by elemental synthesis enhances resistance to viscoplastic deformation at temperatures above 800 • C due to the formation of the Cr 0.5 Mo 0.5 and Cr 0.7 Mo 0.3 phases [31,32]. High-level mechanical properties were attained at 900 • C for the studied samples after HIP: σ ucs = 615 ± 9 MPa; σ ys = 488 ± 7 MPa; and ε pd = 62.2 ± 1.4 %.…”

Optimizing microstructure and mechanical properties of NiAl-9Mo alloy by Zr addition and suction casting process

“…According to Vickers hardness measurements, the suction-cast A3 alloy has a harder surface than the as-cast A3 alloy, with microhardness values of 396 HV and 630 HV, respectively. The microstructure of suction-cast alloy is well refined [11], with narrow eutectic cell sizes [10,12,15], which retains a more even distribution of the Heusler phase formed at the cell boundary, and fine grain strengthening and the second phase strengthening that cooperate in conjunction to improve the alloy's hardness.…”

“…Researchers added Mo to NiAl alloy to create a pseudo-binary eutectic structure in order to improve its characteristics. The room temperature fracture toughness of NiAl-xMo (x =7.8-16) alloy steadily increased with the increase of Mo content, and the room temperature plasticity and fracture toughness of NiAl-Mo alloy were both enhanced [8][9][10][11][12][13][14][15]. One of *Corresponding author: e-mail address: qiyihui@lnut.edu.cn **Corresponding author: e-mail address: wangyongsll@163.com them, NiAl-9Mo alloy, also performs well at high temperatures [9,10,16].…”

Effect of Copper on Microstructure and Performance of WC/NiAl/TiC Composite Coatings by Laser Cladding

“…The NiAl-based material is prepared and investigated to develop various applications, including directed solidification, [3] casting, [4] mechanical alloying methods, [5] and additive manufacturing. [6] The intermetallic compounds of NiAl are characterized by a B2 crystal structure and exhibit a combination of capabilities derived from both metallic and ceramic materials. These characteristics include high thermal conductivity, antioxidant properties, and high-temperature corrosion resistance.…”