Abstract
The effect of test temperature on the hardness (HV) of fine-graind sintered compacts with the average crystal grain size of 0.10-0.35 μm, which were prepared from ultrafine powders of 0.02 μm, was investigated for Fe, Co, Ni, Fe-Co, Fe-Ni, Co-Ni and Fe-Co-Ni systems. The test temperature dependence of Hv for the Fe sintered com-pact was compared with those of medium or coarse-grained sintered compacts of 0.82-3.5 μm.
The results obtained were as follows: (1) The order of Hv observed at room temperature among the alloy systems did not change in general at the higher test temperatures. (2) The Hv of Fe fine-grained compacts decreased sharply at about 500 K, which was much lower than that (about 800 K) for coase-grained compacts of 3.5 μm. This was attributed to the fact that creep deformation easily occurs even at such low temperatures for fine-grained compacts.
