Research On The Microstructure And Properties Of The Fe-1.1Ni-0.5Mo-0.5/1.5Cr Sintered Alloy

Compacting pressure, content of Cr, addition quantity of reduced iron powder and effect of Cr content on sintered alloy tissue and performance have been systematically analyzed with respect to the pre alloy Fe-1.1Ni-0.5Mo-0.5/1.5Cr prepared by inert gas atomization, in which the sintered alloy is produced by applying sinter-hardening process and formability of the pre-alloy matrix powders is improved by adding reduced iron powder with heterotypic particles.The study demonstrates the inferior formability of applying the pre-alloy Fe-1.1Ni-0.5Mo-0.5/1.5Cr from atomization machines. Increase of compacting pressure favors the further compact of alloy powder, raise the density of compacts, strengthen the hardness and intensity of sintering alloy, but results easily in compacts break if it is too high and eventually deteriorates the performance of sintering alloy. There are a large amount of pores in the sintering alloy tissue having mainly martensitic structure, which explains the very low intensity. Experiment datas show that the overall mechanical performance is equivalent for compacting pressure600MPa and800MPa. There are obvious drawbacks like crack and fault on sample surface for800MPa, concluding that the optimal compacting pressure is600MPa. With that value, the overall mechanical performance of Cr0.5is better than that of Crl.5, the density of sintered state is6.88g/cm3, hardness41HRC and tensile strength202MPa.Formality of alloy powders can be improved and production cost reduced by adding reduced iron powder. It is shown that adding them in pre-alloy powders Fe-1.1Ni-0.5Mo-0.5Cr ameliorates the formability of alloy powders, improves the density and intensity of alloy and stability of the size. With the increase of quantity of the reduced iron powder, the density of sintered alloy increases and then decreases and the intensity and strength decreases slightly. The overall performance is the best and the size is stable with the reduced iron powders as high as30%, in which the density is7.07g/cm3, hardness42HRC, and tensile strength635MPa.The experiment uses sample from technology being mainly composed of martensitic structure the hardness, which is mainly related to the percentage of carbon quality in martensitic structure. It also affects indirectly the plasticity and toughness of the martensite. With different content of graphite and research on its effect with respect to the performance of sintered alloy Fe-1.1Ni-0.5Mo-0.5Cr, it is discovered that the density, hardness and intensity of the sintered alloy increase first and then decrease when having more and more carbon. Furthermore, as the value is0.6, the overall mechanical performance is optimal, with sintered density to be7.08g/cm3, intensity44HRC, and tensile strength638MPa.