Performance Benefits in Sintered Steels with Extra-Fine Nickel Powder

摘要

Extra-fine Ni powder has been shown to improve the distribution of Ni-rich phases in sintered steel compared to standard admixed Ni powder. Agglomerate-free powders have been obtained with conventional low-shear mixing. Finer Ni particle size resulted in a higher diffusion rate of Ni at conventional sintering conditions, with a corresponding increase in microindentation hardness of the surrounding steel microstructure. Extra-fine nickel powder forms martensite in sintered steels with furnace cooling. Hardenability measurements were made on both Ni and Ni-Cu alloy samples of variable thickness and cooled in an industrial furnace equipped with accelerated cooling. Recent work on Ni-Cu steels has shown that the distribution of Cu is influenced by the distribution of Ni. Improved Ni-Cu distribution and smaller Ni-Cu-rich phases obtained with extra-fine Ni powder compared to standard Ni powder resulted in sintered samples having smaller and more consistent dimensional change from die size.