Abstract
Eight investment castings of Inconel 713C superalloy were fabricated, varying in the melt-pouring temperature, from 1400 to 1520 °C, and CoAl2O4 inoculant content, 0 or 5 wt.%, in the primary coat. Their influence on grain size on tensile and creep properties was investigated. The best combination of yield stress (815 MPa) and elongation (A4 = 7.65%) at ambient temperature was obtained in surface-modified castings poured from 1520 °C. The longest time to rupture was for the unmodified castings (76.8 h) poured from 1520 °C, while for the modified variant, the time to rupture was lower around, 7.4 h, which was still a satisfactory value. During tensile testing, microcracks were formed in large eutectic γ′, carbides and borides, due to the accumulation of stress at interfaces with the matrix. During creep, N-type rafting of γ′ precipitates and phase transformation MC + γ → γ′ + M23C6 took place.
Highlights
Precipitation-strengthened nickel-based superalloys are widely used in the manufacturing of turbine blades and vanes, which operate in hot sections, both in turbochargers of combustion engines and turbofan jet engines (Ref [1, 2])
The creep properties of castings tested at 982 °C and 151.8 MPa as a function of melt-pouring temperature are presented in Fig. 7(a) and (b)
The main conclusions of the research are: (a) The compound CoAl2O4 is suitable for surface modification of IN713C castings
Summary
Precipitation-strengthened nickel-based superalloys are widely used in the manufacturing of turbine blades and vanes, which operate in hot sections, both in turbochargers of combustion engines and turbofan jet engines (Ref [1, 2]). Grain refinement by the addition of inoculants has several benefits, namely a substantially easy operation, no change in production equipment and a very good refining effect (Ref [13, 14]). It has been reported (Ref 13, 15-18) that inoculants have a favorable influence on grain refinement and low-temperature mechanical properties. The main aim of this research was to determine the influence of the melt-pouring temperature and the CoAl2O4 inoculant in the prime coat of the shell mold on the structure and mechanical properties of IN713C superalloy castings
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