Materials that can maintain a fine-grained structure at high temperatures mainly include microalloyed steel containing Ti, Nb, and V; powder metallurgy steel; heat-resistant alloys (such as Inconel 718); and ceramic matrix composites. These materials effectively suppress grain coarsening at high temperatures through the characteristics of precipitated phases pinning grain boundaries or their own absence of grain structure.
1. Microalloyed Steel (Mainstream Choice)
Ti-containing steel (e.g., H13+Ti): Ti forms highly stable TiC, which is almost insoluble below 1200°C, pinning grain boundaries for a long time and exhibiting the strongest resistance to grain growth;
Nb-containing steel (e.g., H13+Nb): NbC dynamically precipitates during recrystallization, preventing grain engulfment and making it suitable for temperature fluctuation conditions;
V-containing steel (e.g., H13+V): VC exists stably in the 600–900°C range, providing moderate pinning force at a lower cost.
Mechanism: Zener pinning effect – fine, dispersed second-phase particles physically hinder grain boundary migration.
2. Inherently Fine-Grained Steel
Al-Killed H13: AlN is generated through Al deoxidation, pinning grain boundaries in the early stages of heating to prevent excessive austenite grain growth;
Fine-Grained 4Cr5MoSiV1: Deoxidation and cooling rates are controlled during the smelting process to ensure a fine and uniform original microstructure (grain size 5–8).
Features: High cost-effectiveness, suitable for new mold manufacturing, no need to add expensive alloys.
3. Powder Metallurgy Steel (High-End Applications)
PM-H13: Utilizes powder metallurgy technology, achieving an original grain size of 8–10, with extremely uniform carbide distribution, exhibiting far superior resistance to high-temperature coarsening compared to traditional steels;
ASP-23: High-speed steel, containing high levels of V and Mo, with an ultrafine microstructure and abundant dispersed carbides, exhibiting excellent high-temperature resistance.
Advantages: Good isotropy, fatigue life is more than 30% higher than traditional steel, suitable for precision molds in medical, optical, and other fields.
4. Heat-resistant alloys (ultra-high temperature applications)
|
Material |
Maximum service temperature |
Fine grain retention mechanism |
|
Inconel 718 |
1100°C |
γ' phase (Ni₃Al) dispersion strengthening, inhibits grain boundary migration |
|
Haynes 230 |
1150°C |
Solid solution strengthening + carbide precipitation, excellent creep resistance |
|
Stellite 6 |
1000°C |
Carbide network support, strong microstructure stability |
Note: High cost, difficult to process, usually used for partial replacement of critical components.
5. Ceramic Matrix Composites (Frontier Direction)
SiC/SiC, Al₂O₃/ZrO₂: These composites have no metallic grain structure, can withstand temperatures above 1400°C, and exhibit almost no thermal deformation.
Applications: Used as wear-resistant parts such as nozzle liners and flow dividers, in combination with metal matrices.
Trend: Expanding from aerospace to high-end mold manufacturing, representing a future development direction.
