Fe-29Ni-17Co (Kovar alloy) powder mixes were obtained by mixing nickels and cobalt powders with reduced and carbonyl iron powder respectively, and sintered Fe-29Ni-17Co samples were prepared by pressing the powder mixes and sintering at different temperatures. Microstructure and properties of the sintered Fe-29Ni-17Co samples were investigated in accordance with the types of the iron powders and sintering temperature. The results show that sintered Fe-29Ni-17Co samples prepared from the carbonyl iron powder have higher relative density and better comprehensive performance. After sintered at 1250 ℃ for 2 h in H2 atmosphere, relative density of 97.51 % (8.11 g·cm-3) was obtained for samples prepared from the carbonyl iron powders, which is 1.4 % higher than that from reduced iron powders. Hardness and tensile strength of the samples prepared from carbonyl iron powders reach 84.6HRB and 533.8 MPa, respectively, and thermal conductivity, average thermal expansion coefficient (20~400 ℃) and electrical resistivity are 16.45 W·m-1·K-1, 4.71×10-6 K-1 and 0.38 Ω·cm, respectively. More uniform austenite distribution was observed in the sintered samples prepared from carbonyl iron powders, and there have less martensite transformation after low temperature treatment.
DownLoad: