热等静压对第三代单晶高温合金DD33显微组织和持久性能的影响

对第三代DD33单晶高温合金进行标准热处理、热等静压以及不同制度的后续固溶和时效处理,并在850℃/650 MPa和1100℃/170 MPa条件下进行高温持久性能实验,使用金相显微镜(OM)、扫描电子显微镜(SEM)和X射线三维成像技术(XCT)等手段观察和表征不同状态的样品,研究了热等静压和热处理对这种合金显微组织和持久性能的影响。结果表明：铸态DD33单晶高温合金经过适当的热等静压和后续热处理工艺后,样品的组织形貌(γ′相尺寸、体积分数与立方化程度)与标准热处理态基本相同。与标准热处理态合金相比,热等静压处理后合金显微孔洞的体积分数和尺寸均显著降低,其体积分数从0.0190%降低到0.0005%,最大孔等效直径从36.9 μm减小到14.2 μm。在850℃/650 MPa和1100℃/170 MPa条件下热等静压后的样品持久寿命均显著延长。这表明,适当的热等静压和热处理能消除合金内部的显微孔洞缺陷,使其持久性能显著提高。

Effect of Hot Isostatic Pressing on Microstructure of a Third-Generation Single Crystal Superalloy DD33

The third generation DD33 single crystal superalloy was subjected to standard heat treatment and hot isostatic pressing respectively, and then to different post-solution and -aging treatments. Hereafter, the effect of hot isostatic pressing and heat treatment on the microstructure and durability of the alloy were investigated by means of high-temperature endurance tests at 850℃/650 MPa and 1100℃/170 MPa, as well as metallographic microscope (OM), scanning electron microscope (SEM) and X-ray three-dimensional imaging (XCT). The results show that after proper hot isostatic pressing and subsequent heat treatment, the as-cast DD33 single crystal superalloys present more or less the same microstructure of (γ' phase size, volume fraction and cubic degree) as those subjected to standard heat treatment. Compared with the standard heat treated alloy, the volume fraction and size of the micropores of the alloy decreased significantly after hot isostatic pressing, from 0.0190% to 0.0005%, and the maximum equivalent diameter of the micropores decreased from 36.9 μm to 14.2 μm. The durable life of the alloy subjected to hot isostatic pressing was significantly prolonged when testing by 850℃/650 MPa and 1100℃/170 MPa. These results show that proper hot isostatic pressing and heat treatment can eliminate the micro voids, therewith, improve the durability of the alloy.