Ni-Based Welding Alloy High-Temperature Strength and Crack Prevention
Solution Overview
Problem
Conventional Ni-based alloys face challenges in achieving both high strength and weldability at temperatures between 700 to 800°C, with existing materials either lacking sufficient strength or experiencing weld cracks due to thermal stress and solidification segregation.
Innovation Solution
A Ni-based alloy composition with specific mass percentages of C, Co, Cr, Al, Mo+W, and B is developed, optimizing the solid solution temperature and precipitation amount of the γ′ phase to enhance high-temperature strength and weldability, preventing harmful phase formation and ensuring phase stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the strength of Ni-based alloy is increased through precipitation strengthening, then high-temperature strength is improved, but weldability deteriorates due to low ductility and thermal stress
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ranges of alloying elements (Al: 2.0-4.0%, Ti: 0.05-0.20%, Nb: 0.05-0.20%, V: 0.05-0.20%, C: 0.03-0.10%) to adjust the precipitation behavior of γ′ phase. By optimizing these parameters, the alloy achieves high-temperature strength through controlled γ′ precipitation while maintaining sufficient ductility and weldability, resolving the contradiction between strength improvement and manufacturability deterioration
Solution Approach 2:
The patent employs composite material principles by creating a multi-element alloy system that combines Ni base with carefully selected additions of Al, Ti, Nb, V, C, Cr, Co, and Mo. This composite composition enables synergistic effects where different elements contribute to strength mechanisms (γ′ precipitation, solid solution strengthening, dispersion strengthening) while collectively maintaining weldability, thus resolving the strength-weldability contradiction
2Ease of manufacture
If the solid solution temperature of γ′ phase is lowered to improve weldability, then ease of manufacture is improved, but high-temperature strength deteriorates due to insufficient γ′ phase precipitation
Solution Approach 1:
The patent uses parameter changes by optimizing the Al content (2.0-4.0%) and adding multiple microalloying elements (Ti, Nb, V, C) to control the γ′ phase precipitation characteristics. This composition design allows the alloy to maintain adequate γ′ precipitation at service temperatures (700-800°C) for high-temperature strength while having a lower solid solution temperature (840°C or lower) for improved weldability, thus resolving the contradiction between manufacturability and high-temperature performance
3Strength
If conventional alloying is used to achieve sufficient strength at 700-800°C, then high-temperature strength is improved, but harmful phases are generated due to solidification segregation, reducing reliability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ranges of multiple elements to suppress harmful phase formation. The optimized Al content (2.0-4.0%), combined with Ti (0.05-0.20%), Nb (0.05-0.20%), V (0.05-0.20%), and C (0.03-0.10%), creates a composition that promotes beneficial γ′ precipitation while suppressing harmful phase formation during solidification and service, thus resolving the contradiction between strength and reliability
Solution Approach 2:
The patent converts the potential harm of solidification segregation into a benefit by using controlled microalloying additions. The small amounts of Ti, Nb, V, and C that might otherwise form harmful segregated phases are instead used to create fine, controlled precipitation of beneficial γ′ and other strengthening phases, transforming the segregation issue into a strength enhancement mechanism while maintaining phase stability
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 achieves high-temperature strength and excellent weldability, preventing weld cracks and maintaining material integrity at 700 to 800°C, suitable for applications in power-generating plants and high-temperature components.
Implementation Method 1
a weld crack possibly generates when the γ′ phase precipitates during the welding or cooling
Implementation Method 2
A large thermal stress generates in the metal material during cooling, since it shrinks during the solidification
Implementation Method 3
at a temperature of 700 to 800° C., which is a service temperature, a structural change occurs due to atom diffusion
Data Source
AI summary
A Ni-based alloy for a welding material including, by mass, 0.001 to 0.1% of C, 18 to 25% of Co, 16 to 20% of Cr, 2.5 to 3.5% of Al, 9.0 to 15.0% of Mo+W, 0.001 to 0.03% of B and the balance being Ni and inevitable impurities.