Nickel-Based Superalloy Grain Refinement via CrFeNb
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Solution Overview
Problem
Nickel-based superalloys produced by selective laser melting often exhibit anisotropic columnar grain structures due to high temperature gradients and cooling rates, leading to adverse mechanical properties and reduced service life.
Innovation Solution
A method involving ball milling and drying of IN718 alloy powder with a CrFeNb alloy powder as a grain refiner, followed by selective laser melting, to transform the grain structure from columnar to equiaxed, thereby improving mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective laser melting is used to produce nickel-based superalloy, then high density and good forming quality can be achieved, but anisotropic columnar grain structure is produced leading to poor mechanical properties
Solution Approach 1:
The patent applies preliminary action by adding a grain refiner alloy powder to the metal powder before selective laser melting. This grain refiner is prepared in advance and mixed with the base alloy powder, serving as a nucleating agent that promotes equiaxed grain formation during the melting process, thereby preventing the development of anisotropic columnar grains while maintaining high forming quality
Solution Approach 2:
The patent changes the microstructural parameters by controlling the particle size distribution of the metal powder (D10-D90 ratio) and adjusting the composition of the grain refiner alloy. These parameter changes enable the transformation from columnar to equiaxed grain structure, improving mechanical properties while preserving the high density and forming quality achieved through selective laser melting
2Productivity
If high temperature gradient and high cooling rate are generated during selective laser melting, then rapid solidification is achieved, but anisotropic columnar grain structure is produced
Solution Approach 1:
The grain refiner alloy powder acts as an intermediary substance that mediates between the high temperature gradient/cooling rate conditions and the desired equiaxed grain structure. The grain refiner particles serve as nucleation sites that promote uniform grain growth, counteracting the tendency toward columnar grain formation caused by the steep temperature gradients inherent in selective laser melting
Solution Approach 2:
The patent changes the thermal-microstructural parameters by optimizing the particle size distribution of the metal powder (specifically the D10-D90 ratio) and the composition of the grain refiner. These parameter adjustments enable the system to achieve rapid solidification while promoting equiaxed grain growth, thereby maintaining both high productivity and grain structure uniformity
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 method achieves yield strengths of at least 710 MPa and tensile strengths of at least 1010 MPa at room temperature, with significant improvements after heat treatment, enhancing the alloy's overall mechanical performance without introducing impurity elements.
Implementation Method 1
subjecting the mixed powder obtained in step (1) to a selective laser melting to obtain the nickel-based superalloy
Implementation Method 2
selective laser melting
Implementation Method 3
the grain refiner being a CrFeNb alloy powder... promote the formation of equiaxed grains
Data Source
AI summary
Disclosed are a nickel-based superalloy formed by selective laser melting and a preparation method thereof. In the method, CrFeNb alloy powder is used as a grain refiner, and its element composition is within the composition range of a nickel-based superalloy powder to ensure that the prepared nickel-based superalloy has the same element composition with the original alloy; the grain size in the nickel-based superalloy could be refined by the addition of CrFeNb alloy powder, such that the anisotropic columnar grain structure in the alloy is transformed to equiaxed grain structure, thereby improving mechanical properties of the alloy.