Study On Technologies And Properties Of Y₂O₃ Reinforced Cr-Ni Matrix Composite

Ni-base superalloys which develop from Ni80Cr20 were important alloy of the high-temperature materials used in gas turbines. Oxide Dispersion Strengthened (ODS) superalloys was produced by mechanical alloying process followed by conventional processing and heat treatment processes. ODS superalloys was one of the new high-temperature composites, which shows good hot strength properties at about 700°C and at temperature as high as 90% of theirs melting point. The excellent properties of ODS superalloys are due to the very fine dispersion of stable, incoherent oxide particles. These particles act as barriers to the movement of dislocations.In this paper, Ni80Cr20 superalloy and Y₂O₃/Cr-Ni composites powder were prepared by mechanically alloying, which produced the composite by the powder metallurgy method. The weight percent of Y₂O₃ are 0.3%, 0.4%, 0.6%, 0.8%, 1.0% and1.2%. High temperature simulation for mechanical properties was carried out based on the Larson-Miller equation.Comparing the Y₂O₃/Cr-Ni composites prepared by this method with the Ni80Cr20 superalloy prepared by this method and the Y₂O₃/Cr-Ni composites prepared by conventional powder metallurgy method, we could find:1. The experiment suggested that the Vicker's hardness was approximately proportional to the heat treatment parameter P after the simulation, no matter the Y₂O₃/Cr-Ni composites prepared by mechanically alloying method or that prepared by the conventional powder metallurgy method. This shows that the Larson-Miller equation is applicable for the lifespan design of the Y₂O₃/Cr-Ni composite, which would reduce the experiment and production cost of this kind of composites greatly.2. The experiment suggested that the Y₂O₃/Cr-Ni composites prepared by mechanically alloying method showed good mechanical performance at either room temperature or high temperature. At room temperate, the tensile strength of the Y₂O₃/Cr-Ni composite containing 0.8% weight fraction of Y₂O₃ is 52% higher than 20CrNi alloy, their hardness is 43% higher than 20CrNi alloy, at the same time, their elongation and reduction in area both decreased by 30% or so than 20CrNi alloy. After heat treatment at 1200°C for 40 hour, the tensile strength of the Y₂O₃/Cr-Ni composite containing 0.8% weight fraction of Y₂O₃ is 87% higher than 20CrNi alloy, their hardness is 54% higher than 20CrNi alloy, and their elongation and reduction in area are both 20% lower than 20CrNi alloy.3. The experiment also showed that, at room temperature, the tensile strength of the Y₂O₃/Cr-Ni composite prepared by mechanically alloying method is 22% higher than that prepared by the conventional powder metallurgy method, their hardness is 43% higher than that prepared by the conventional powder metallurgy method; on the other hand, after heat treatment at 1200°C for 40 hour, the hardness of the Y₂O₃/Cr-Ni composite prepared by mechanically alloying method is 16% higher than the Y₂O₃/Cr-Ni composite prepared by the conventional powder metallurgy method.