Grain Size Control in Forged Superalloy Components
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Solution Overview
Problem
Current methods for producing forged superalloy articles often result in non-uniform grain sizes, leading to reduced low cycle fatigue resistance and mechanical properties, as they struggle to simultaneously achieve coarser grains for creep resistance and finer grains for fatigue resistance within a single component.
Innovation Solution
A method involving the formation of a fine-grained billet through powder consolidation, followed by forging at a subsolvus temperature to achieve high total strains, and subsequent heat treatments to pin grain boundaries and control grain size, allowing for differential grain sizes within regions of the component during supersolvus processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional forging is performed to achieve desired component shape, then manufacturing efficiency is improved, but non-uniform grain sizes are produced reducing overall mechanical properties
Solution Approach 1:
The patent applies preliminary action by performing subsolvus heat treatment on the hub region before the final supersolvus heat treatment. This preliminary thermal processing establishes a fine-grained microstructure in the hub that is then protected during the subsequent supersolvus treatment, ensuring uniform grain size control throughout the manufacturing process while maintaining production efficiency.
Solution Approach 2:
The patent implements dynamic control of heat treatment parameters by using different temperature-time profiles for different regions. The process dynamically adjusts thermal conditions: subsolvus temperatures for the hub to maintain fine grains, and supersolvus temperatures for the rim to achieve coarse grains, thereby achieving uniform grain size control without sacrificing manufacturing efficiency.
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
This approach effectively suppresses grain growth, enabling precise control of grain size and enhancing mechanical properties such as creep resistance and low cycle fatigue resistance in specific regions of the component, particularly beneficial for gas turbine engine components.
Implementation Method 1
subsequent heat treatments to pin grain boundaries and control grain size
Implementation Method 2
gamma double-prime (γ′′) precipitation-strengthened nickel-based superalloys
Data Source
AI summary
Components and methods of processing such components from precipitation-strengthened alloys so that the components exhibit desirable grain sizes following a supersolvus heat treatment. The method includes consolidating a powder of the alloy to form a billet having an average grain size. The billet is then forged at a temperature below the solvus temperature to form a forging having an average grain size of not coarser than the grain size of the billet. The billet is then forged at a total strain of at least 5%, after which at least a portion of the forging is heat treated at a temperature below the solvus temperature to pin grains within the portion. The entire forging can then be heat treated at a temperature above the solvus temperature of the alloy without coarsening the grains in the portion.