Studies of oxide reduction during sintering of Cr alloyed PM steel by coupled experimental and diffusion simulations

• Oxide reduction in Cr alloyed PM steel has been simulated experimentally by measuring the oxygen loss from powders when exposed to a heating cycle, by photo acoustic spectroscopy (PAS) and by thermogravimetric analysis (TGA). Pressed samples were heated in dry hydrogen gas using a defined, slow, heating rate up to 1300oC. The oxides in the powder are reduced by the hydrogen gas. From the PAS curves distinct reduction temperatures are observed, that can be correlated to the type of oxide by comparing with thermodynamic calculations of the oxide stabilities. The experimental results were analyzed by diffusion simulations that involve a description of the diffusion controlled oxide reduction. It is shown how the calculated rate of oxygen diffusion in the samples, compared with the experimental results, has been applied as a tool for increased understanding of the reduction during sintering.

Nyckelord

Acoustic spectroscopy

Chromium alloys

Diffusion

Photoacoustic spectroscopy

Sintering

Thermogravimetric analysis

Diffusion controlled

Dry hydrogen

Heating cycles

Hydrogen gas

Oxide reduction

Oxygen diffusion

Reduction temperatures

Thermodynamic calculations

Powder metallurgy

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