Influence of Melt Superheating Treatment on Solidification Characteristics and Rupture Life of a Third-Generation Ni-Bas
- PDF / 2,462,716 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 91 Downloads / 145 Views
Influence of Melt Superheating Treatment on Solidification Characteristics and Rupture Life of a Third-Generation Ni-Based Single-Crystal Superalloy HAIJUN SU, HAIFENG WANG, JUN ZHANG, MIN GUO, LIN LIU, and HENGZHI FU The influence of melt superheating treatment on the melt properties, solidification characteristics, and rupture life of a third-generation Ni-based single-crystal superalloy was investigated to reveal the critical temperature range of melt structure evolution and its effect on rupture life. The results showed that the viscosity of superalloy decreased but the surface tension increased with increasing superheating temperature. Two characteristic temperature points where the melt viscosity and undercooling degree suddenly change were determined to be 1600 C and 1700 C, respectively. Similarly, the stability of the solidification interface firstly improved and then weakened with increasing superheating temperature. The dendrite arms were well refined and the segregation was reduced at 1700 C. In addition, the rupture life obtained at 1100 C and 137 MPa increased by approximately 30 pct, approaching the rupture life of the corresponding superalloy containing 2 pct Ru, with increasing superheating temperature from 1500 C to 1700 C. When the melt was further heated to 1800 C, the rupture life decreased. The evolutions of solidification characteristics and rupture life with increasing melt superheating temperature were attributed to changes in the melt structure. https://doi.org/10.1007/s11663-018-1256-1 The Minerals, Metals & Materials Society and ASM International 2018
I.
INTRODUCTION
NI-BASED single-crystal superalloys possess outstanding high-temperature mechanical properties under extreme working environments; hence such superalloys have been widely used to manufacture turbine blades of aircraft and land gas turbine engines.[1,2] Recently, refractory elements have been added to Ni-based single-crystal superalloys to increase the liquidus and working temperatures in order to meet the demand of higher inlet gas temperature in turbine engines.[3–5] However, when refractory elements are introduced, the costs and densities of superalloys are greatly enhanced. Further, excess of refractory elements can cause severe segregation and promote the formation of harmful phases,[6] thereby deteriorating the mechanical properties and increasing subsequent solution heat treatment costs. At present, it has been well verified that appropriate melt superheating treatment can effectively reduce
HAIJUN SU, HAIFENG WANG, JUN ZHANG, MIN GUO, LIN LIU, and HENGZHI FU are with the State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi an, 710072, P.R. China. Contact e-mail: [email protected] Manuscript submitted September 2, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
the segregation and dendrite arm spacing, and improve the long-term strengths of superalloys.[7,8] Moreover, melt superheating treatment can change the morphologies of precipitation phases and control phase selectio
Data Loading...
