Three-Phase Controlled Expansion Superalloys with Oxidation Resistance

Abstract

Due to their low coefficients of thermal expansion, lNCOLOY@ alloys 903, 907 and 909 have contributed to improved efficiency in many aircraft engines designed since the mid '70's. The application of these Cr-free superalloys was, however, limited by inadequate oxygen environment resistance. The alloys were susceptible to both general oxidation and SAGBO (Stress Accelerated Grain Boundary Oxygen) embrittlement. Until just recently development efforts had focused on improving SAGBO resistance, but had ignored general oxidation resistance.* Compositions shown are in weight % unless stated otherwise.

Precipitation behaviour of β and γ′ in high Al low thermal expansion superalloy

“…As shown in Table 1 in Ref. 7 and Fig. 2 in this study, the formation of b consumes much Al; therefore, an Al depleted zone can form around b phase.…”

“…[1][2][3][4][5][6][7][8] However, as has been observed in another high Al low thermal expansion superalloy, EXP. alloy 4005, both NiAl type b and Ni 3 Al type c9 phases are Al enriched as shown in Table 1, 7 which indicates that the precipitation of b and c9 phases should be correlated. The precipitation of c9 phase assures the good creep and strength properties at high temperatures, which have been widely investigated in many superalloys.…”

“…In comparison with conventional low coefficient of thermal expansion (CTE) alloys, it contains higher Al (5?4 wt-%), which leads to the precipitation of both NiAl type b phase and Ni 3 Al type c9 phase in the Co-Ni-Fe based c matrix. [1][2][3][4][5][6][7][8] Most of the investigations in IN783 alloy are focused on the precipitation of b phase as well as its effect on mechanical properties. [1][2][3][4][5][6][7][8] However, as has been observed in another high Al low thermal expansion superalloy, EXP.…”

“…[1][2][3][4][5][6][7][8] Most of the investigations in IN783 alloy are focused on the precipitation of b phase as well as its effect on mechanical properties. [1][2][3][4][5][6][7][8] However, as has been observed in another high Al low thermal expansion superalloy, EXP. alloy 4005, both NiAl type b and Ni 3 Al type c9 phases are Al enriched as shown in Table 1, 7 which indicates that the precipitation of b and c9 phases should be correlated.…”

Thermal Stability of Inconel Alloy 783 at 593�C and 704�C

“…It has a specially designed austenitic matrix for good hot/cold workability, fine Ni 3 Al-type gamma prime for high strength, and inter-and intra-granular NiAl-type beta phase for good SABGO and general oxidation / corrosion resistance [2,3]. This study presents a comparative * INCONEL and INCOLOY are the registered trademarks of the Special Metals Family of Companies thermal stability of alloys 783 and 909 at 593°C and 704° C. The materials were high temperature tensile tested following extended high exposure.…”