The heat treatment process for high-temperature alloys refers to a metal thermal processing technique in which high-temperature alloy materials undergo heating, holding, and cooling in a solid state to achieve the desired microstructure and performance. In recent years, two heat treatment processes have been extensively and systematically studied: solution heat treatment and aging heat treatment.
Solution Heat Treatment involves heating the alloy to the complete dissolution temperature of precipitated phases, ensuring that all non-uniformly distributed precipitates dissolve fully into the matrix. This strengthens the solid solution, improves toughness and corrosion resistance, eliminates residual stress, facilitates further processing, and prepares the material for subsequent aging treatment, ensuring uniform precipitation of strengthening phases.
Aging Heat Treatment entails heating and holding the alloy within the temperature range where the strengthening phases precipitate, allowing these phases to uniformly precipitate and distribute, along with carbides. This process enhances the alloy's hardness and strength.
Heat Treatment of GH4145 High-Temperature Alloy
GH4145 is a nickel-based, age-hardening alloy with [Ni₃(Al, Ti, Nb)] as its primary strengthening phase. It is mainly used for high- and intermediate-pressure inner cylinder flange bolts in 300MW and 600MW steam turbines. After prolonged high-temperature operation, these bolts undergo changes in microstructure and dislocation configuration, along with precipitation of strengthening phases, leading to creep and reduced long-term performance.
To restore performance, bolts with a post-operation hardness of 333 HBW were subjected to recovery heat treatment using a solution + dual aging process:
Solution treatment: 1130℃ × 1h, oil quenching
First aging: 845℃ × 24h, air cooling
Second aging: 707℃ × 20h, air cooling
After this treatment, the bolt hardness was reduced to within the required standard range. Although there was a slight decrease in strength, both plasticity and toughness improved significantly, demonstrating the effectiveness of the recovery heat treatment process.
Heat Treatment of GH4169 High-Temperature Alloy
GH4169 is a Nb-containing high-strength nickel-chromium-iron-based superalloy, primarily used for high-temperature components in aerospace engines. The heat treatment process significantly affects the microstructure and properties of cold-rolled GH4169 blades.
A softening treatment was performed at 970–995°C, followed by intermediate and solution aging treatments:
Intermediate treatment: 900℃, air cooling
Solution aging treatment: 1010℃, air cooling → 720℃ × 8h, furnace cooling → 620℃ × 8h, air cooling
The softening treatment significantly reduced hardness, facilitating the second cold rolling process. When treated at 995℃, optimal softening was achieved without adverse effects on the alloy's microstructure. After cold rolling, softening treatment had little impact on mechanical properties, whereas intermediate treatment and final solution aging heat treatment played a decisive role in determining mechanical properties.
Development Trends in High-Temperature Alloy Heat Treatment
High-temperature alloys undergo heat treatment under strictly controlled heating and cooling conditions to modify their microstructure, optimizing performance and service life. As new high-temperature alloy materials emerge and higher performance demands arise, heat treatment processes remain indispensable. Current development trends include:
1.Integration of Heat Treatment with Alloy Design – Optimizing alloy composition alongside heat treatment and other processing techniques to achieve the best performance matching.
2.Computational Simulation & Process Innovation – Using computer modeling to analyze alloy deformation and heat treatment behavior. Process control systems are being enhanced, with simultaneous development of new equipment and innovative heat treatment techniques.
3.Phase Transformation Studies – The relationships and mechanisms governing phase transitions among precipitates during service and heat treatment remain unclear and require further research.
4.Optimization of Quenching Media – Investigating appropriate quenching media and improving quenching processes will be a key focus of future research.
5.Expansion of Vacuum Heat Treatment – Vacuum heat treatment, which offers oxidation-free, decarburization-free, and low-distortion advantages, is expected to see wider application in aerospace and other industries.
6.Plasma Surface Treatment – Plasma surface modification techniques, including ion nitriding, ion nitrocarburizing, and ion carburizing, offer benefits such as wear resistance, minimal distortion, improved appearance, and no blind spots. These methods will become increasingly popular in high-temperature alloy applications.
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We specialize in the R&D and production of titanium alloys, high-temperature alloys, high-entropy alloys, and refractory metals, including tungsten, molybdenum, tantalum, niobium, zirconium, titanium, and nickel.
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