Ni-BASED SUPER-HEAT-RESISTANT ALLOY FOR AIRCRAFT ENGINE CASES, AND AIRCRAFT ENGINE CASE FORMED OF SAME

Abstract

Provided are a Ni-based heat resistant superalloy for aircraft engine cases excellent in high-temperature characteristic such as tensile characteristics and low-cycle fatigue characteristics in a high-temperature range and also excellent in workability, and an aircraft engine case formed of the same. The Ni-based heat resistant superalloy has composition containing, by mass, Co: 4.0 to 11.0%, Cr: 12.0 to 17.0%, Al: 2.0 to 4.0%, Ti: 2.0 to 4.0%, Al+Ti: 4.6 to 6.7%, Mo: more than 5.5 to 10.0%, W: more than 0 to 4.0%, B: 0.001 to 0.040%, C: 0.02 to 0.06%, Zr: 0 to 0.05%, Mg: 0 to 0.005%, P: 0 to 0.01%, Nb: 0 to 1.0%, Ta: 0 to 1.0%, and Fe: 0 to 2.0%, and the balance of Ni with inevitable impurities, and is suitable for aircraft engine cases.

1 . A Ni-based heat resistant superalloy having a composition consisting of, by mass,
 Co: 4.0 to 11.0%,   Cr: 12.0 to 14.8%,   Al: 2.0 to 4.0%,   Ti: 2.0 to 4.0%,   Al+Ti: 4.6 to 6.7%,   Mo: more than 5.5 to 10.0%,   W: more than to 4.0%,   B: 0.001 to 0.040%,   C: 0.02 to 0.06%,   Zr: 0.005 to 0.05%,   Mg: up to 0.005% (including 0%),   P: up to 0.01% (including 0%),   Nb: up to 1.0% (including 0%),   Ta: up to 1.0% (including 0%),   Fe: up to 2.0% (including 0%), and   the balance of Ni with inevitable impurities,   wherein a difference between solvus temperature T 1  of an M 6 C carbide and solvus temperature T 2  of a γ′ phase (T 1 −T 2 ) calculated from thermodynamic calculation based on the composition of the Ni-based heat resistant superalloy by CALPHAD method satisfies −30° C.≤(T 1 −T 2 )≤+40° C., and   wherein the Ni-based heat resistant superalloy has a tensile strength at 750° C. of at least 1000 MPa according to ASTM E21 using test specimen.   
     
     
         2 . The Ni-based heat resistant superalloy according to  claim 1 , wherein the number of cycles to failure in a low-cycle fatigue test in a total strain range of 0.6% at 750° C. is at least 1.0×10 5 . 
     
     
         3 . The Ni-based heat resistant superalloy according to  claim 1 , wherein in the composition, Al+Ti is 5.2 to 6.7% by mass. 
     
     
         4 . An aircraft engine case formed of the Ni-based heat resistant superalloy according to  claim 1 .