How does SLM compare to casting in strength and durability for superalloys?

Microstructure and Density

SLM produces a fine and uniform microstructure with rapid solidification rates, which results in higher strength compared to traditional casting. However, casting methods such as vacuum investment casting or directional casting can create fully dense structures, especially when followed by hot isostatic pressing (HIP). SLM parts may require HIP to eliminate residual porosity and achieve equivalent density levels.

Mechanical Strength and Fatigue Performance

Due to rapid cooling, SLM parts often show higher tensile strength but slightly lower fatigue resistance than cast components. With proper post-treatment—such as heat treatment and HIP—SLM-built superalloys like Inconel 600 and Hastelloy X can match or exceed the fatigue strength of equiaxed cast parts. Directionally solidified and single-crystal castings still provide superior creep resistance for turbine hot-section components.

Dimensional Accuracy and Design Flexibility

SLM offers greater flexibility for complex designs and tight tolerances. Casting is ideal for large components and traditional geometries, while SLM excels at producing internal cooling channels and lattice structures. Finish machining—such as EDM and CNC machining—is often required for both processes to finalize critical areas.

Application Considerations

When long-term durability and creep resistance are required, cast superalloys—especially those produced through single crystal casting—remain unmatched. However, for rapid prototyping, lightweight structures and near-net-shape production, SLM provides substantial manufacturing advantages. In many cases, hybrid manufacturing combines SLM pre-forms with casting or forging followed by post-process treatments to achieve optimal performance.