Grain Size Control in Laser Additive Manufacturing of Turbine Disks
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Solution Overview
Problem
Gas turbine engine disks face challenges due to radial temperature and stress gradients, requiring different mechanical properties in rim and hub regions, with existing additive manufacturing techniques failing to effectively control grain size for optimal creep resistance and fatigue performance.
Innovation Solution
The method involves additively manufacturing turbine disks with bimodal radial grain size distributions by controlling laser power and scan speed in laser powder bed fusion, resulting in larger grains in the rim region for high temperature creep resistance and smaller grains in the hub region for high fatigue resistance, using processes like selective layer melting and laser powder bed fusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single grain size is used throughout the disk, then manufacturing is simplified, but the disk cannot simultaneously achieve optimal creep resistance in the rim and fatigue resistance in the hub
Solution Approach 1:
The patent applies local quality by creating different grain sizes in different regions of the disk. The rim region is engineered with larger grains to optimize creep resistance under high temperature conditions, while the hub region is engineered with smaller grains to optimize fatigue resistance under high stress conditions. This regional differentiation of microstructural properties directly resolves the contradiction between achieving optimal reliability in both regions versus maintaining uniform manufacturing simplicity.
Solution Approach 2:
The patent utilizes parameter changes by modifying laser processing parameters (power, scan speed, hatching distance) during additive manufacturing to control grain size in different regions. By dynamically adjusting these processing parameters, the system achieves different grain sizes in the rim and hub regions without requiring separate manufacturing processes, thus resolving the contradiction between tailored microstructural properties and manufacturing complexity.
2Manufacturing precision
If laser power is increased, then melting and fusion are improved, but grain size increases which reduces fatigue resistance
Solution Approach 1:
The patent resolves this contradiction by dynamically changing laser parameters during manufacturing. In the hub region where fatigue resistance is critical, the system uses lower laser power and/or faster scan speeds to produce smaller grains. In the rim region where high temperature performance is critical, the system uses higher laser power to produce larger grains with better creep resistance. This spatial variation of processing parameters resolves the contradiction between fusion quality and fatigue resistance.
3Productivity
If scan speed is increased, then manufacturing productivity is improved, but grain size decreases which may compromise creep resistance
Solution Approach 1:
The patent resolves this contradiction by dynamically changing scan speed during manufacturing. In the hub region where fatigue resistance is critical, the system uses higher scan speeds to produce smaller grains. In the rim region where high temperature performance is critical, the system uses lower scan speeds to produce larger grains with better creep resistance. This spatial variation of processing parameters resolves the contradiction between productivity and 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
This approach enables the creation of functionally graded structures with tailored mechanical properties, enhancing creep performance and fatigue resistance in turbine alloys, as demonstrated by manipulating grain sizes in Inconel 718 coupons.
Implementation Method 1
forming a first fused rim region of the layer of alloy powder with the first grain size by scanning the first fused rim region with a laser at a first laser power and a first scan speed
Implementation Method 2
forming a second fused hub region of the layer of alloy powder with the second grain size by scanning the second fused hub region with the laser at a second laser power and a second scan speed
Data Source
AI summary
An additively manufactured alloy component has a first portion formed of the alloy and having a first grain size, and a second portion formed of the alloy and having a second grain size smaller than the first grain size. In an embodiment, the alloy component is an alloy turbine disk, the first portion is a rim region of the alloy turbine disk, and the second portion is a hub region of the alloy turbine disk. The first and second grain sizes may be achieved by controllably varying the laser power and/or scan speed during additive manufacturing.