Tag: powders

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%.

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 […]

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Boron Carbide Density

The density of boron carbide (B4C) is 2.51 x 103kg/m3.

Boron carbide is an extremely hard, low-density ceramic and covalent material, which ranks third behind diamond and cubic boron nitride. Its high hardness makes it suitable as an abrasive. It is also used to make tools, nozzles and nuclear reactor neutron absorbers.

The density of B4C is a function of the melting point and the thermal expansion coefficient. It is a very good control material for high-temperature reactors because of its high thermal neutron capture cross section and the fact that the reaction rates and irradiation are uniform throughout the absorber.

Phase constitution, morphology and stoichiometry of synthesized powders were investigated by X-ray diffraction and field-emission scanning electron microscopy (FESEM). The effect of heating temperature and starting composition on phase constitution, morphology as well as stoichiometry were also determined.

A series of boron carbide powders were synthesized at 1900 degC from precursor mixtures with different molar ratios of B2O3/C. The stoichiometric B4C powders had an average grain size of 300 nm. The powders exhibited a highly uniform crystalline structure and showed a strong crystal symmetry between the carbon and boron atoms.

During heat treatment, the powders underwent a combination of liquid-solid and gas-solid reactions, resulting in fine-sized and elongated platelet B4C powders. These powders are characterized by a relatively large pore volume and an indentation resistance of 40000 BHN, which is comparable to diamond. In addition, they are wear-resistant and semiconductive.

The density of boron carbide (B4C) is 2.51 x 103kg/m3.Boron carbide is an extremely hard, low-density ceramic and covalent material, which ranks third behind diamond […]

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