γ′相对高钨镍基高温合金拉伸和持久变形行为的影响

Effect ofγ’-phase on Tensile and Stress Rupture Deformation Behavior of High W-containing Ni-based Superalloys

对K416B高钨高温合金进行固溶和时效处理以调整其中γ′相的形貌使其具有两种尺寸,研究了铸态和热处理态合金的拉伸和持久变形行为。结果表明,铸态K416B合金中的γ′相在基体中分布均匀,其平均尺寸为200 nm,能有效阻碍位错在基体中运动从而使其屈服强度提高。在热处理态的K416B合金中析出了两种γ′相,其尺寸分别为1μm和100 nm。在热处理态K416B合金的室温拉伸过程中全位错剪切大尺寸初生γ′相和以Orowan机制绕过小尺寸二次γ′,使其屈服强度降低。在高温下二次γ′相更容易粗化而使γ基体的宽度增大,促进位错剪切γ′相而使持久应变速率提高。同时,在持久变形过程中纳米级W6C颗粒在γ-γ′相界面弥散析出消耗大量W元素降低γ-γ′两相的错配度,使合金的强化水平下降而导致其持久寿命大幅度降低。

Ni-based superalloys with high W content are widely used to fabricate gas turbine blades because of their high temperature mechanical properties and lower cost.Theγ′-phase is the most important strengthening phase in Ni-based superalloys,which affects the deformation behavior during tensile process.Although the influence ofγ′-phase has been studied extensively,there are few investigations on the deformation mechanism of K416B superalloy with different morphologies ofγ′-phase.Hence,the effect ofγ′-phase morphology on the mechanical behavior of K416B superalloy was assessed in the present work.The average size ofγ′-phase scattered in the as-cast alloy was about 200 nm,which could impede the mobility of dislocations in the matrix so that the yield strength increased.After heat treatment,two sizes ofγ′-phase precipitated from the matrix,the size of them were 1μm and 100 nm respectively.During room temperature tensile deformation of the alloy after being subjected to heat treatment,dislocations could fully share the primaryγ′-phase particles,and even detour the secondaryγ′-phase particles per Orowan mechanism,therewith the yield strength of the alloy decreased.The life of as-cast K416B is longer than that of the heat-treatment counterpart.It can be interpreted that the secondaryγ′-phase particles coarsened rapidly during the durable test.Additionally,the precipitation of nano W6C particles along theγ-γ′interface depleted tungsten in the alloy,which reduced the mismatch betweenγandγ′phases,resulting in the damage of the durable life of K416B alloy.