CX stainless steel is one type of martensitic precipitation-hardening (PH) stainless steel powder. It is often branded as EOS stainless steel CX, and sometimes classified in research context as a 12Cr-9Ni-2Al type alloy.

It is a tooling-grade stainless steel characterized by having a good corrosion resistance combined with high strength and hardness. It is typically used for plastic injection molding tools and rubber molding tools.

Its solution annealing normally takes 30 minutes at 850 °C followed by rapid air cooling to room temperature.

CX powder produced by gas atomization, but also can by PREP for better sphericity and lower hollow particles, typically is used in additive manufacturing, particularly Laser Powder Bed Fusion (LPBF) and electron bean melting.