Effect of reducing agents on the sintering of chromium alloyed PM steels

• The control of the surface chemistry during sintering is the key factor for the successful and efficientproduction of PM parts, especially for powders containing elements with high affinity to oxygen such as chromium.The effect of different reducing agents was investigated by performing sintering trials on water atomized steel powder pre-alloyed with 3 wt.% Cr with and without the addition of graphite as well as using atmospheres with varying hydrogen content. The use of thermal analysis and photoacoustic spectroscopy in combination with results from fractographic investigation showed that oxide reduction is enhanced with the presence of hydrogen even if the main reduction mechanism is the carbothermal reactions. Oxides rich in Cr, Mn and Si were formed during sintering for all appliedconditions. The findings are summarized in a simple model describing the enclosure of oxides during the sinter-neckdevelopment and the changes in surface chemistry during the process.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Annan materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Other Materials Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

oxide enclosure

Cr-prealloyed powder

Oxide reduction

sintering atmosphere

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