Cobalt Alloy Powder Composition for High-Temperature Creep
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Solution Overview
Problem
Cobalt-based alloy materials lack sufficient mechanical properties compared to precipitation-strengthened nickel-based alloy materials, particularly in high-temperature applications, and do not achieve the same level of creep durability and tensile strength as γ′ phase precipitation-strengthened nickel-based alloys.
Innovation Solution
A cobalt-based alloy powder and sintered body with a specific composition, including carbon, boron, chromium, iron, nickel, tungsten/molybdenum, titanium, zirconium, niobium, tantalum, hafnium, vanadium, silicon, manganese, nitrogen, and cobalt, with segregated cells of average size between 0.15 μm and 4 μm, which enhances precipitation strengthening and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cobalt-based alloy materials use conventional compositions and processing methods, then they achieve basic mechanical properties, but they cannot reach the mechanical property levels (creep durability and tensile strength) of γ′ phase precipitation strengthened nickel-based alloy materials
Solution Approach 1:
The invention changes the chemical composition parameters of the cobalt-based alloy by precisely controlling the content ranges of key elements: C (0.05-0.30 mass%), Cr (10-30 mass%), Ni (5-30 mass%), Fe (3-15 mass%), W (3-12 mass%), Mo (3-12 mass%), and specific alloying elements (Ti, Zr, Nb, Ta, Hf, V totaling 0.1-2.0 mass%). These parameter changes enable the alloy to achieve mechanical properties equivalent to or exceeding γ′ phase precipitation strengthened nickel-based alloys.
Solution Approach 2:
The invention creates a composite microstructure within the cobalt-based alloy by combining multiple strengthening mechanisms: precipitation strengthening from carbide phases (formed by C with Cr, Mo, W, and other alloying elements), solid solution strengthening from Cr, Ni, Fe, and other elements in the cobalt matrix, and grain boundary strengthening. This composite approach enables the alloy to reach the required mechanical property levels for high-temperature turbine applications.
2Strength
If cobalt-based alloy materials are designed for high-temperature strength, then they achieve improved mechanical properties, but their cost increases due to higher material costs compared to nickel-based alloy materials
Solution Approach 1:
The invention optimizes the composition parameters to balance performance and cost by setting specific content ranges: Cr (10-30 mass%) for corrosion resistance and carbide formation, Ni (5-30 mass%) for solid solution strengthening, Fe (3-15 mass%) as a cost-effective strengthening element, and W (3-12 mass%) + Mo (3-12 mass%) for high-temperature strength. This parameter optimization achieves γ′ phase precipitation strengthened nickel-based alloy equivalent performance at lower material cost.
3Strength
If cobalt-based alloy materials use higher carbon content to enhance precipitation strengthening, then they achieve improved mechanical properties, but their corrosion resistance deteriorates
Solution Approach 1:
The invention precisely controls the carbon content parameter within 0.05-0.30 mass% to achieve optimal precipitation strengthening while maintaining corrosion resistance. Simultaneously, it controls Cr content at 10-30 mass% to ensure sufficient corrosion resistance and forms carbide precipitates through the synergistic interaction of C with Cr, Mo, and W, achieving both strength and corrosion resistance requirements.
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 cobalt-based alloy material achieves mechanical properties equivalent to or exceeding those of precipitation-strengthened nickel-based alloys, including a 100,000-hour creep durable temperature of 875°C or higher and a tensile proof stress of 500 MPa or more at room temperature, making it suitable for high-temperature turbine components.
Implementation Method 1
researches have been made about precipitation strengthening by a carbide phase
Data Source
AI summary
A Co based alloy powder includes between 0.08% and 0.25% mass of carbon, 0.1% mass or less of boron, between 10% and 30% mass of chromium, 5% mass or less of iron, and 30% mass or less of nickel; the iron and the nickel in a total amount of 30% mass or less; includes at least one of tungsten and molybdenum in a total amount of between 5% and 12% mass; includes at least one of titanium, zirconium, niobium, tantalum, hafnium, and vanadium in a total amount of between 0.5% mass and 2% mass; includes 0.5% mass or less of silicon, 0.5% mass or less of manganese, and between 0.003% and 0.04% mass of nitrogen; and includes cobalt and impurities as the balance of the powder. Crystal grains included in the cobalt-based alloy powder have segregated cells; the cells have an average size of between 0.15 μm and 4 μm.