Влияние легирующих добавок молибдена и рения на структуру и свойства литого сплава NiAl–Cr–Co

A centrifugal SHS casting technology was used to obtain NiAl–Cr–Co–(X) alloys where X = 2.5÷15.0 wt.% Mo and up to 1.5 wt% Re. The study covers the effect of modifying additives on the combustion process as well as the phase composition, structure, and properties of cast alloys. Alloying up to 15 % Mo and 1.5 % Re provided the highest improvement of properties in relation to the base alloy in terms of overall performance. Molybdenum formed a plastic matrix and improved strength properties to the following values: uniaxial compressive strength σ ucs = 1730±30 MPa, yield strength σ ys = 1560±30 MPa, plastic component of deformation e pd = 0.95 %, and annealing at t = 1250 °С improved them to: σ ucs = 1910±80 MPa, σ ys = 1650±80 MPa, e pd = 2.01 %. Rhenium modified the alloy structure and improved its properties to: σ ucs = 1800±30 MPa, σ ys = 1610±30 MPa, e pd = 1.10 %, and annealing further improved them to: σ ucs = 2260±30 MPa, σ ys = 1730±30 MPa, e pd = 6.15 %. The mechanical properties of the NiAl, (Ni,Cr,Co) 3 Mo 3 C, Ni 3 Al, (Cr, Mo) and MoRe 2 phases, as well as the hypothetical Al(Re,Ni) 3 phase, were determined by the nanoindentation method. According to the Guinier–Preston structural transformation, local softening upon annealing at t > 850 °С increases the proportion of plastic deformation during compression tests due to the lost coherence of the boundaries of nanosized plate-shaped Cr-based precipitates with a supersaturated solid solution. A hierarchical three-level structure of the NiAl–Cr– Co–15%Mo alloy was established: the first level is formed by β-NiAl dendritic grains with interlayers of molybdenum-containing phases (Ni,Co,Cr) 3 Mo 3 C and (Mo 0.8 Cr 0.2 ) x B y with a cell size of up to 50 μm; the second one consists of strengthening submicron Cr(Mo) particles distributed along grain boundaries; the third one is coherent nanoprecipitates of Cr(Mo) (10–40 nm) in the body of β-NiAl dendrites. The cast alloy mechanical grinding techniques were used to obtain a precursor powder with an average particle size of D av = 33.9 μm for subsequent spheroidization.