Influence of elements powder pre-alloying technology on microstructure and property of sintered alloy-steel

In order for elaborating the function of alloying elements to raise the strength of ferrous-base sintered alloy material and to speed-up the development of the corresponding products with median/high strength in our country three kind of powders were used to prepare the sintered alloy-steel containing 2%Ni, 1.5%Cu, 0.5%Mo and 0.4%C, which were admixed powder, partially(diffusely) prealloyed powder and fully prealloyed powder. The powder's compacts were sintered at 1150℃ in vacuum atmosphere. The results show that the structure depends on the microchemistry, the change in microchemistry bring about the complex structure; the nonuniform microstructure is observed in the specimen made from admixed powder, which consists of pearlite, ferrite and martensite; the microstructure of the specimen made from partially prealloyed powder consists of pearlite, ferrite, martensite and bainite. The microstructure of specimen made from fully prealloyed powder consists of carbide particles in ferrite matrix and characterizes by a dimple ductile fracture; the mechanical properties are raised a lot for the compacts made from partially prealloyed powder and fully prealloyed powder, as the quenched samples their tensile strength σ_b were 968MPa and 1027MPa respectively, while impact toughness α_k are 26J/cm 2 and 30J/cm 2 respectively.