Nickel-Based Alloy Composition for Additive Manufacturing Cracking Resistance
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Solution Overview
Problem
Nickel-based superalloys manufactured through additive manufacturing processes face challenges in achieving a balance between high strength, low density, and resistance to hot cracking and strain-age cracking, with existing alloys being difficult to process and having insufficient structural integrity.
Innovation Solution
A nickel-based alloy composition is developed with tailored chemistry to enhance resistance to hot cracking and strain-age cracking, optimized through the Alloys-by-Design method, which balances alloying elements to achieve a desired microstructural architecture and improved processability, incorporating specific weight percentages of elements like aluminum, titanium, niobium, and tantalum to minimize γ′ precipitation and promote a stable chromia scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional nickel-based superalloys are used for additive manufacturing, then high strength and creep resistance can be achieved, but hot cracking and strain-age cracking resistance deteriorate
Solution Approach 1:
The patent modifies the chemical composition parameters of nickel-based superalloys by controlling the content of alloying elements (Al: 1.5-4.5%, Ti: 1.1-3.4%, Nb: 0.0-4.0%, Ta: 0.0-5.2%, W: 0.9-6.6%, Mo: 0.0-3.0%, Co: 0.0-24.0%, Cr: 12.5-20.6%) to achieve an optimal balance between strength and cracking resistance. This parameter optimization reduces γ′-phase precipitation that causes strain-age cracking while maintaining high strength properties.
Solution Approach 2:
The patent creates a composite microstructure consisting of multiple phases (γ matrix, γ′ precipitates, and chromia scale) with specific volume fractions and distributions. The γ′-phase strengthened alloy combines the strength benefits of precipitate hardening with the cracking resistance provided by controlled microstructural architecture and stable chromia protective scale.
2Strength
If high γ′ content is used to achieve high strength, then creep resistance improves, but strain-age cracking susceptibility increases
Solution Approach 1:
The patent optimizes the composition parameters of γ′-forming elements (Al, Ti, Nb, Ta) to control the volume fraction and distribution of γ′ precipitates. By maintaining specific ratios and total content levels, the alloy achieves adequate γ′ content for creep resistance while preventing excessive precipitation that would lead to strain-age cracking.
3Ease of manufacture
If alloy chemistry is optimized for hot cracking resistance, then processability improves, but strength and creep resistance may deteriorate
Solution Approach 1:
The patent adjusts the chemical composition parameters to reduce hot cracking susceptibility by controlling elements that affect solidification behavior and microstructural development. Simultaneously, strength-enhancing elements are maintained at levels that ensure high strength while enabling additive manufacturing processability.
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 alloy exhibits improved resistance to hot cracking and strain-age cracking, maintaining structural integrity while offering high strength, creep resistance, and oxidation resistance, enhancing its suitability for additive manufacturing processes.
Implementation Method 1
This can be achieved by having a sufficiently high ratio of chromium to titanium to form a stable and continuous protective chromia scale
Implementation Method 2
Hot cracking occurs during the last stages of solidification process with a strong dependence on alloy chemistry
Implementation Method 3
Strain-age cracking occurs because of two principal factors: residual strain and γ′ precipitation
Data Source
AI summary
A nickel-based alloy composition consisting, in weight percent, of: 1.5 to 4.5% aluminium, 1.1 to 3.4% titanium, 0.0 to 4.0% niobium, 0.0 to 5.2% tantalum, 0.9 to 6.6% tungsten, 0.0 to 3.0% molybdenum, 0.0 to 24.0% cobalt, 12.5 to 20.6% chromium, 0.02 to 0.15% carbon, 0.001 to 0.015% boron, 0.0 to 0.1% zirconium, 0.0 to 3.0% rhenium, 0.0 to 2.0% ruthenium, 0.0 to 3.0% iridium, 0.0 to 0.5% vanadium, 0.0 to 1.0% palladium, 0.0 to 1.0% platinum, 0.0 to 0.5% silicon, 0.0 to 0.1% yttrium, 0.0 to 0.1% lanthanum, 0.0 to 0.1% cerium, 0.0 to 0.003% sulphur, 0.0 to 0.25% manganese, 0.0 to 0.1 magnesium, 0.0 to 5.0% iron, 0.0 to 0.5% copper, 0.0 to 1.0% hafnium, the balance being nickel and incidental impurities, wherein the following equations are satisfied in which WAl, WTi, WNb, WTa and WW are the weight percent of aluminium, titanium, niobium, tantalum and tungsten in the alloy respectively0.65≤0.3WNb+0.15WTa3.6≤WAl+0.5WTi+0.3WNb+0.15WTa≤5.7WTa+0.92WW≤6.1