Ni-Based Hot-Forging Die Alloy for Oxidation-Resistant Strength
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Solution Overview
Problem
Ni-based heat-resistant super alloys used in hot forging dies exhibit high-temperature compressive strength but suffer from oxidation resistance issues, leading to surface deterioration and shape degradation due to nickel oxide scaling during cooling in air.
Innovation Solution
A Ni-based alloy composition with specific ranges of W, Mo, Al, Cr, Ta, S, rare-earth elements, Zr, Hf, Ti, Nb, Co, C, and B is developed to enhance high-temperature compressive strength while improving oxidation resistance and suppressing scale formation and precipitation of harmful phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Ni-based heat-resistant super alloys are used in hot forging dies to achieve high-temperature compressive strength, then the die can operate at high temperatures (1000°C or more), but oxidation resistance deteriorates causing nickel oxide scale formation and scattering during cooling in air
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the Ni-based alloy. Specifically, it limits Al to 5.0-7.5% and Cr to 0.5-3.0% to prevent excessive oxide scale formation, while adding rare-earth elements (0.003-0.05%) and Zr (0.03-0.1%) to modify oxide characteristics and improve adhesion. This compositional parameter optimization resolves the contradiction between maintaining high-temperature strength and improving oxidation resistance.
Solution Approach 2:
The patent creates a composite material system by combining Ni-based super alloy with specific additions of rare-earth elements and Zr. This composite approach leverages the high-temperature strength of the Ni-based matrix while the rare-earth and Zr additions form a protective oxide layer composite that adheres better to the substrate, preventing scale scattering and improving overall oxidation resistance.
2Reliability
If Al and Cr content are increased to improve oxidation resistance, then oxidation protection is enhanced, but high-temperature compressive strength decreases
Solution Approach 1:
The patent optimizes the parameter range of Al to 5.0-7.5% and Cr to 0.5-3.0%, avoiding excessive additions that would harm strength. Within these controlled ranges, the alloy achieves sufficient oxidation resistance through the synergistic effect of these elements forming protective oxides, while maintaining high-temperature compressive strength through the Ni-based matrix and other strengthening elements.
Solution Approach 2:
The patent introduces rare-earth elements and Zr as intermediary substances that mediate between the metal matrix and the oxide scale layer. These intermediaries modify the oxide formation process and improve adhesion between the oxide layer and the metal substrate, enabling effective oxidation protection at lower Al and Cr content levels, thus preserving high-temperature strength.
3Ease of operation
If the die is heated to high temperature for forging poor workability materials, then workability of the material improves, but the die surface oxidizes and scales scatter causing environmental deterioration and shape degradation
Solution Approach 1:
The patent converts the harmful oxidation process into a beneficial protective mechanism. By controlling the composition to form a stable, adherent oxide layer containing rare-earth and Zr oxides, the normally harmful oxidation that causes scale scattering is transformed into a protective barrier that prevents further oxidation and eliminates scale scattering, thus protecting both the die and the working environment.
Solution Approach 2:
The patent modifies the chemical composition parameters to change the oxidation behavior of the die surface. The specific additions of rare-earth elements (0.003-0.05%) and Zr (0.03-0.1%), combined with controlled Al and Cr content, alter the oxidation kinetics and oxide morphology to produce a stable, non-scattering oxide layer that protects the die during high-temperature operation.
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 high-temperature compressive strength and excellent oxidation resistance, preventing environmental and shape deterioration in hot forging processes, as demonstrated by reduced scale scattering and increased Charpy impact values.
Implementation Method 1
oxidation resistance, preventing environmental and shape deterioration in hot forging processes, as demonstrated by reduced scale scattering
Data Source
AI summary
Provided are a Ni-based alloy for hot die having a high high-temperature compressive strength and a good oxidation resistance and being capable of suppressing the deterioration in the working environment and the shape deterioration, and a hot forging die made of the Ni-based alloy for hot die. The Ni-based alloy for hot die comprises, in mass %, W: 7.0 to 15.0%, Mo: 2.5 to 11.0%, Al: 5.0 to 7.5%, Cr: 0.5 to 3.0%, Ta: 0.5 to 7.0%, S: 0.0010% or less, one or two or more selected from rare-earth elements, Y, and Mg in a total amount of 0 to 0.020%, and the balance of Ni with inevitable impurities. In addition to the composition described above, one or two elements selected from Zr and Hf can further be contained in a total amount of 0.5% or less.