Bonding Evolution with Sintering Temperature in Low Alloyed Steels with Chromium Articles uri icon

publication date

  • May 2009

start page

  • 161

end page

  • 173

issue

  • 2

volume

  • 41

international standard serial number (ISSN)

  • 0350-820X

electronic international standard serial number (EISSN)

  • 1820-7413

abstract

  • At present, high performance PM steels for automotive applications follow a processing route that comprises die compaction of water-atomized powder, followed by sintering and secondary treatments, and finishing operations. This study examines Cr-alloyed sintered steels with two level of alloying. In chromium-alloyed steels, the surface oxide on the powder is of critical importance for developing the bonding between the particles during sintering. Reduction of this oxide depends mainly on three factors: temperature, dew point of the atmosphere, and carbothermic reduction provided by the added graphite. The transformation of the initial surface oxide evolves sequence as temperature increases during sintering, depending on the oxide composition. Carbothermic reduction is supposed to be thecontrolling mechanism, even when sintering in hydrogen-containing atmospheres. The effect of carbothermic reduction can be monitored by investigating the behavior of the specimens under tensile testing, and studying the resultant fracture surfaces.