Studies On Preparation And Mechanical Properties Of γ'-phase Reinforced Nickle Matrix Composite

Nickel-base superalloys have excellent properties at high temperature.It is important materials in the manufacturing of modern aircraft engines,rocket engines and gas turbines.Most of the nickel-base superalloys were developed on the basis of the Cr20-Ni alloy.Oxide Dispersion Strengthened(ODS) nickel-base composites have superior properties at high temperature,which is paid more attention in the aerospace industries.Theγ'-phase depositions precipitated through aging treatment could improve the heat resistance of composites at middle temperature.Therefore,oxide particles andγ'-phase precipitates working together were thought could to expand the application temperature range of nickel-base superalloys.Theγ'-phase strengthened nickel-base superalloys were made by powder-metallurgy using Cr20-Ni alloys as matrix.We studied the effects of Al addition in nickel-base superalloys.We Also studied the effects of yttrium oxide particles inγ'-phase strengthened nickel-base superalloys.The high temperature performance of the composites were simulated according to Larson-Miller parameter equations.The experiments show:1.Aging parameters influence the quantity and shape of theγ'-phase precipitates.Improper treatment time and temperature would degrade the strengthening effects ofγ'-phase precipitates.We found that aging at 760℃for 24 hours could bring in the best effect to the materials.We also found that Al has weaker solution strengthening effect than Cr has if it only works as a solid solution element in the matrix.2.The mechanical properties ofγ'-phase strengthened nickel-base superalloys decreased rapidly at high temperature.For example,when the heat simulation parameter was 31825,the hardness ofγ'-phase strengthened nickel-base superalloys was only 170HV at high temperature,while it was 337HV at room temperature.The hardness decreased by 50%.However,the Hardness ofγ'-Y₂O₃/NiCrAl composite only decreased by 31%,which indicates that the composite has better heat resistance,theγ'-Y₂O₃ dispersions working together has stronger strengthening effect.3.The test results of heat simulation are well agreed to Larson-Miller parameter equations.It shows that Larson-Miller parameters equations are accurate and applicable for the simulation of these composite materials,which can greatly reduce the costs of testing or manufacturing of similar materials.