Cold-Rolled Ni-Cr-Ti-Al Seal Alloy for 900°C Stability
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Solution Overview
Problem
Current seal members made from general-purpose Ni-base alloys lose high-temperature strength at temperatures above 800°C due to phase changes, and adding Co to enhance strength compromises workability and increases costs, while maintaining sealing properties at 900°C is challenging.
Innovation Solution
A γ′ precipitation-hardening cold-rolled band material with a specific composition (Ni: 40-62%, Cr: 13-20%, Ti: 1.5-2.8%, Al: 1.0-2.0%, Nb: 2.0% or less, Ta: 2.0% or less, B: 0.001-0.010%, W: 3.0% or less, Mo: 2.0% or less, and optional elements like Co and Cu) that maintains γ′ phase stability and mechanical strength even at 900°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If general-purpose Ni-base alloys are used for seal members, then high-temperature strength is maintained up to 800°C, but the seal property is reduced at temperatures above 800°C due to phase changes (γ′ phase transforms to δ phase or disappears)
Solution Approach 1:
The invention changes the compositional parameters of the Ni-base alloy by precisely controlling the amounts of Ni (40-62%), Cr (13-20%), Ti (1.5-2.8%), and Al (1.0-2.0%) to stabilize the γ′ phase at high temperatures. This parameter optimization prevents the phase transformation that occurs in general-purpose alloys, maintaining seal property at temperatures above 800°C.
Solution Approach 2:
The invention creates a composite microstructure consisting of the Ni-base matrix with stabilized γ′ phase precipitates. This composite structure maintains its integrity at high temperatures, providing both strength and sealing capability where conventional single-phase materials fail.
2Strength
If Co is added to enhance high-temperature strength, then creep strength is improved, but workability in cold rolling deteriorates and cost increases
Solution Approach 1:
The invention optimizes the compositional parameters by controlling Ni (40-62%), Cr (13-20%), Ti (1.5-2.8%), and Al (1.0-2.0%) to achieve high-temperature strength without requiring excessive Co addition. This parameter optimization maintains cold rolling workability while providing the necessary creep strength at 900°C.
3Quantity of substance
If Ni amount is decreased to reduce cost, then manufacturing cost is reduced, but γ′ phase stability deteriorates at high temperatures
Solution Approach 1:
The invention optimizes the compositional parameters by precisely controlling Ni (40-62%), Cr (13-20%), Ti (1.5-2.8%), and Al (1.0-2.0%) to stabilize the γ′ phase at high temperatures. This parameter optimization maintains phase stability even with reduced Ni content compared to conventional alloys, achieving cost reduction without sacrificing high-temperature performance.
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 solution effectively suppresses the disappearance of fine precipitates, maintaining sealing properties and mechanical strength over long-term high-temperature exposure, with enhanced creep strength and workability without excessive Co addition.
Implementation Method 1
a γ′ precipitation-hardening cold-rolled band material
Implementation Method 2
γ′ phase or γ′′ phase, which are a precipitation phase providing high-temperature strength at 800° C. or more, changes to δ phase not contributing to high-temperature strength
Data Source
AI summary
A seal member includes a γ′ precipitation-hardening alloy, in which the γ′ precipitation-hardening alloy has a component composition of, in mass %: Ni: from 40 to 62%; Cr: from 13 to 20%; Ti: from 1.5 to 2.8%; Al: from 1.0 to 2.0% (provided that Ti/Al: 2.0 or less); Nb: 2.0% or less; Ta: 2.0% or less (provided that Nb+Ta: from 0.2 to 2.0%); B: from 0.001 to 0.010%; W: 3.0% or less; and Mo: 2.0% or less (provided that Mo+(1/2)W: from 1.0 to 2.5%), and optionally, C: 0.08% or less; Si: 1.0% or less; Mn: 1.0% or less; P: 0.02% or less; and S: 0.01% or less, with the balance being Fe and inevitable impurities, and in which the seal member has a hardness of 250 Hv or more, and includes a cold-rolled microstructure obtained by a cold rolling.