Ni-based Superalloy Phase Transformation Creep Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nickel-base superalloys used in jet engine turbine disks face limitations in operating temperature due to creep deformation above 700°C, where diffusion-mediated processes and γ segregation along superlattice stacking faults reduce their strength and resistance to shearing.
Innovation Solution
Incorporating specific amounts of eta and chi phase formers, such as titanium, tantalum, and tungsten, to promote shear-induced solid-state transformations from the γ′ phase to the eta and chi phases, inhibiting γ segregation and twin/ribbon formation, thereby enhancing creep strength at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the operating temperature is increased to improve efficiency and reduce emissions, then the efficiency increases and emissions are reduced, but the materials start to plastically deform through creep deformation above 700°C
Solution Approach 1:
The patent changes the chemical composition parameters of the superalloy by specifying precise ranges of alloying elements (Co: 17-20 wt%, Cr: 9-11 wt%, Al: 5.5-6.5 wt%, Ti: 2.5-3.5 wt%, Ta: 4-6 wt%, Mo: 2-4 wt%, W: 2-4 wt%, Nb: 1-1.5 wt%, Hf: 0.25-0.5 wt%) to achieve improved creep resistance at high temperatures through compositional optimization
Solution Approach 2:
The patent creates a composite microstructure consisting of γ phase matrix with γ′ precipitates and controlled stacking fault characteristics, combining multiple phases and structural features to achieve both high temperature strength and creep resistance
2Strength
If the γ′ phase precipitate volume is increased to improve high temperature strength, then the strength at 700°C increases, but diffusion-mediated creep processes and γ segregation along stacking faults become more prevalent above 700°C
Solution Approach 1:
The patent modifies the local structure within the γ′ precipitates by controlling stacking fault characteristics and γ segregation behavior, creating different properties within the precipitate structure itself rather than uniformly changing the entire material
Solution Approach 2:
The patent changes the chemical composition parameters to control γ segregation along stacking faults, specifically adjusting the ratios of γ-forming elements (Co, Cr, Mo, W, Nb, Hf) to γ′-forming elements (Al, Ti, Ta) to prevent detrimental segregation and maintain creep resistance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The local phase transformation strengthening mechanism significantly improves creep properties by doubling the energy required for dislocation nucleation and suppressing nanotwinning and ribbon formation, allowing the superalloy to maintain strength and resistance above 700°C, thus extending the operating temperature and efficiency of jet engines.
Implementation Method 1
promote shear-induced solid-state transformations from the γ′ phase to the eta and chi phases
Implementation Method 2
diffusion-mediated processes, such as the development of superlattice intrinsic stacking faults (SISFs) or superlattice extrinsic stacking faults (SESFs)
Implementation Method 3
heating the superalloy above 700° C. to local phase transformation strengthen the superalloy
Data Source
AI summary
A local phase transformation strengthened nickel-base superalloy includes at least 8.0 wt % eta phase formers; at least 7.0 wt % of chi phase formers; less than 12 wt % chromium; at least 18 wt % cobalt; and aluminum. A ratio of eta phase formers:aluminum is (3.2-3.4):1. The eta phase formers can include titanium, tantalum, hafnium, and niobium. The chi phase formers include tungsten and molybdenum. When the superalloy is subjected to elevated temperatures, these levels of components promote eta and chi phase formation along superlattice stacking faults, thereby resulting in a local phase transformation at the stacking faults, which strengthens the superalloy and inhibits creep deformation.