What High-Temperature Alloys Are Most Commonly Used in SLM 3D Printing?
Nickel-Based Superalloys: The Primary Workhorses
Nickel-based superalloys dominate SLM (Selective Laser Melting) for high-temperature applications due to their excellent strength, creep resistance, and weldability. The most common and well-characterized alloys include:
Inconel 718: The most prevalent 3D-printed superalloy. It offers an outstanding combination of high strength up to ~650°C, good fatigue resistance, and excellent processability. Its relatively slow age-hardening response minimizes cracking risk during printing, making it ideal for a wide range of aerospace and oil and gas components.
Inconel 625: Prized for its superb corrosion and oxidation resistance rather than ultimate strength. It is readily printable and used for static components, ducting, and heat exchangers in aggressive environments, including marine and chemical processing applications.
Haynes 282 & CM247LC: These represent more advanced, higher-temperature-capability alloys. While more challenging to print due to crack sensitivity, optimized SLM parameters and post-processing make them suitable for turbine blades and combustor components that operate beyond the limits of Inconel 718.
Cobalt-Chromium Alloys for Wear and Biocompatibility
Cobalt-based alloys are another major category, valued for exceptional wear resistance, biocompatibility, and high-temperature stability.
CoCrMo (ASTM F75): Extremely common in both aerospace for wear parts and in medical for implants. Its high hardness and corrosion resistance make it a standard for SLM-printed turbine seal segments, dental frameworks, and orthopedic implants.
Haynes 188: A cobalt-nickel-chromium-tungsten alloy offering outstanding oxidation resistance and good strength up to ~1100°C. It is used for aerospace combustor liners and other high-heat static components.
Titanium Alloys for Specific High-Strength Applications
While their maximum use temperature (~600°C) is lower than superalloys, titanium alloys are crucial for high strength-to-weight ratio applications.
Ti-6Al-4V (Grade 5): The most common titanium alloy in all additive manufacturing. It is extensively used for lightweight, high-strength aerospace components like brackets, housings, and some compressor parts. Its printability is excellent.
Ti-6Al-2Sn-4Zr-2Mo (Ti-6242): Offers better creep resistance and higher temperature capability than Ti-6Al-4V, making it suitable for more demanding engine components.
Specialized Stainless Steels and Refractory Metals
For specific temperature ranges and properties, other alloys are employed:
17-4PH & 15-5PH: Precipitation-hardening stainless steels are commonly printed for applications requiring high strength, good corrosion resistance, and temperatures up to ~315°C, such as tooling and certain engine housings.
Refractory Metals (e.g., Tantalum, Tungsten): Used in extreme environments (e.g., >2000°C) for rocket nozzles or furnace components. SLM processing of these materials is highly specialized due to their extremely high melting points.
Key Considerations for SLM Processability
The "common use" of an alloy in SLM is heavily influenced by its weldability and susceptibility to cracking. Alloys with high aluminum and titanium content (for gamma-prime strengthening) are often prone to solidification and strain-age cracking during the rapid thermal cycles of printing. Therefore, widely used SLM alloys like Inconel 718 and 625 are often "weldable" variants. Successful printing of more advanced alloys typically requires meticulous parameter optimization, pre-heating of the build plate, and mandatory post-process Hot Isostatic Pressing (HIP) and heat treatment to achieve required properties.
