When stainless steel can’t meet the requirements, superalloys are needed. Superalloys offer better heat and corrosion resistance. They are used to make engine components and chemical processing equipment. Manufacturers mainly use the investment casting process to produce these parts.
What Are High-Performance Alloys?
High-performance alloys, also called superalloys, are metal materials. They maintain excellent properties even under high temperatures, high pressure, and in highly corrosive environments.
They have the following characteristics:
- Heat Resistance: They keep high strength and resist deformation at temperatures up to 80% of their melting point.
- Oxidation & Corrosion Resistance: They form a stable, dense oxide layer that protects them at high temperatures or in various corrosive chemicals.
- Fatigue Resistance: They can withstand repeated heating and cooling cycles, or repeated stress cycles, without developing cracks or failing.
- Microstructural Stability: Their internal microstructure does not undergo harmful changes even after long-term exposure to high temperatures.
The table below simply compares superalloys with standard stainless steels:
| Performance indicators | Superalloy (e.g., Inconel 718) | Austenitic stainless steel (e.g., 304 stainless steel) |
| Maximum applicable temperature | Approximately 980°C-1200°C | Approximately 870°C |
| High-temperature strength | Extremely high. Maintains high strength at 800°C | Decreases rapidly with increasing temperature |
| Oxidation resistance | Extremely excellent. Forms Al₂O₃ or Cr₂O₃ protective films | Good. But prone to oxide scale at high temperatures |
| Corrosion resistance | Excellent. Resists various acids, alkalis, and salt spray corrosion | Good. But prone to pitting in chloride environments |
| Typical applications | Turbine blades, aerospace engine components | Chemical containers, pipelines, household appliances |
Nickel-Based Alloys
These alloys use nickel as the base element, typically over 50%. They are strengthened by adding elements like chromium, molybdenum, niobium, titanium, and aluminum.
Key Properties:
- Unmatched High-Temperature Performance: They retain the highest level of strength at extreme heat. This is achieved through two main mechanisms: solution strengthening and precipitation strengthening.
- Excellent Corrosion Resistance: Chromium provides outstanding resistance to oxidation. Molybdenum and tungsten further enhance the ability to withstand corrosive, reductive environments.
- Good Weldability and Formability: Many nickel-based alloys are easier to weld and process compared to other superalloys. This allows for the manufacture of complex structural components.
Applications:
- Aerospace: Turbine blades, guide vanes, combustion chambers, turbine discs. This is the most representative application for nickel-based alloys.
- Power Generation: Hot-section components, steam generator tubes, heat exchangers.
- Chemical Processing: Valves, pumps, reactors.
- Automotive: Turbocharger turbines and exhaust valves.
Note: Casting nickel-based alloys requires extremely precise control over melting and solidification. We use vacuum melting and vacuum pouring. This prevents gas porosity and element loss. It ensures high material purity. Our shell-making technology and gating system design also provide excellent control over the casting’s grain structure and directional solidification.
Cobalt-Based Alloys
Cobalt serves as the base element, typically accounting for over 40% of the composition. They are strengthened by adding elements like chromium and tungsten. They can outperform nickel-based alloys in certain specific properties.
Key Properties:
- Excellent Thermal Fatigue & Hot Corrosion Resistance: They last longer in environments with repeated heating and cooling cycles. They also resist corrosive media like sulfides more effectively.
- Superior High-Temperature Wear Resistance: Hard carbide particles spread evenly throughout the base material. This makes them the top choice for high-temperature wear applications.
- Relatively Lower High-Temperature Strength: Their strength generally falls below that of advanced nickel-based alloys above approximately 1040°C. However, their outstanding thermal fatigue resistance compensates for this.
Applications:
- Aerospace: Guide vanes, combustion chamber liners, seals. This is the most representative application for cobalt-based alloys.
- Medical Implants: Artificial joints (e.g., hips, knees).
- Industrial Wear Parts: High-temperature valves, valve seats, wear plates, cutting dies.
- Glass Manufacturing: Forehearths, crucibles, and forming tools for glass melting furnaces.
Note: Casting cobalt-based alloys is difficult because they have a very high melting point and can react with mold materials. We have extensive experience in selecting ceramic shell materials. We match the shell material to the alloy’s pouring temperature to prevent harmful reactions. Our heat treatment processes maximize the alloy’s wear resistance and high-temperature performance.
Special Corrosion-Resistant Alloys
These alloys are used in highly corrosive chemical environments. Many are based on nickel or cobalt.
Key Properties:
- Broad Corrosion Resistance: They resist various strong acids, alkalis, and chloride stress corrosion cracking, including attacks from hydrochloric, sulfuric, hydrofluoric, and phosphoric acids.
- Excellent Pitting & Crevice Corrosion Resistance: They contain high levels of chromium, molybdenum, and nitrogen. This makes them particularly stable in chloride-rich environments.
- Good Mechanical Properties: They maintain high strength and toughness at room and moderate temperatures.
Applications:
- Chemical Processing: Reactors, heat exchangers, agitators, piping systems.
- Marine & Offshore: Seawater pumps, propellers, ship thrusters, offshore platform components.
- Oil & Gas: Downhole tools, valves, flanges, pipelines.
- Pollution Control: Scrubbers and fans in flue gas desulfurization systems.
Note: For these alloys, the casting’s density and surface quality are crucial for corrosion resistance. We provide precision post-treatment processes, including pickling and passivation. This ensures the casting surface forms a complete and stable passive film.
Why Partner with QD?
Precision Melting Control:
We fully use Vacuum Induction Melting and Electroslag Remelting technologies. This allows precise control of alloy composition. It minimizes gas content and impurity elements. This ensures high material purity.
Advanced Shell System:
We scientifically select high-purity materials like zircon sand, fused silica, and alumina. This is based on the chemical properties and pouring temperatures of different alloys. A stable shell means less metal-mold reaction, higher dimensional accuracy, and cleaner casting surfaces.
Customized Heat Treatment:
We have comprehensive heat treatment equipment and a process database for solutions like solution and aging treatment. We create a customized heat treatment plan for each alloy and component. We precisely control temperature, time, and cooling rate. This achieves the required mechanical properties.
When your project faces extreme temperatures, corrosion, or wear challenges, consider QD your reliable manufacturing partner.
FAQ
1. What is the typical lead time for superalloy castings?
Superalloy castings require complex processes. Their production cycle is usually longer than that of standard carbon or stainless steel castings. The typical lead time is 8 to 14 weeks. The exact time depends on the part complexity and inspection requirements.
2. How do you ensure the castings are free of internal defects?
All our critical castings must undergo Non-Destructive Testing. This includes Radiographic Testing, Liquid Penetrant Testing, and Ultrasonic Testing.
3. What material certification documents can we receive?
We provide a complete Material Test Report. This includes chemical composition analysis, mechanical property test results, and NDT reports. These documents ensure your castings meet specifications.
4. What are the maximum and minimum casting sizes QD can handle?
We specialize in producing precision castings weighing from 0.1 kilograms to 400 kilograms. For special requirements outside this range, we can evaluate them on a case-by-case basis and provide the optimal technical solution.
5. Can we provide our own design and material specifications?
Yes, absolutely. We welcome customer-provided drawings and specifications. Our team will work with you to optimize the design for better castability and guaranteed performance.