Stainless Steel Powder for Additive Manufacturing (AM) Applications

Stainless steel is a group of iron-base alloys that contain sufficient chromium to form a stable passive film on the surface (passivate). This makes them corrosion resistant and a good choice for applications in aqueous environments.

SS powders are available in different shapes and particle sizes for additive manufacturing (AM) applications. The range includes basic austenitic, martensitic and ferritic grades with a chromium content of 12 to 30%.

Particle size and shape of 316L powder are an important factor in the suitability of the powder for AM. These properties are also critical for the fabrication of parts with a smooth, flat and well-defined surface finish.

To assess the effect of powder size and shape on rheology, the as-received and spheroidized powders were measured for flowability using a Freeman Technology-FT4 powder rheometer. Additionally, stability tests were carried out in a 25 mm x 25 mm vessel to measure bulk and flow properties.

The relationship between the particle size and shape and the powder rheology was studied with a number of methods, including SEM-EDX, inductively coupled plasma optical emission spectroscopy and electron backscattered diffraction. The chemistry of the powders was also determined using ICP spectroscopy, and the microstructure of the powder was assessed by X-ray diffraction.

The tensile properties of parts produced from the experimental powders were compared to those from commercial and arc-sprayed powders. The parts exhibited similar tensile strength and elongation values, but the arc-sprayed powder specimens showed significant work hardening to a UTS of 974 MPa with an elongation to fracture of 18%.