Havnes282耐热合金组织与性能研究

发布时间：2018-01-12 15:21

本文关键词：Havnes282耐热合金组织与性能研究　出处：《昆明理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：Haynes282合金是时效强化型镍基高温合金,由于蠕变强度高、高温组织稳定性好以及较好的热加工性能,而被选作700℃先进超超临界火电机组汽轮机转子候选材料之一。汽轮机转子材料要求在700℃下具有较高的高温强度、组织稳定性、抗氧化性和焊接性等,为保证Haynes282合金在700℃蒸汽参数下的使用寿命,研究其在700℃甚至更高温度下长期时效及不同应力持久过程中的组织演变和力学性能变化就显得尤为重要。实验研究了固溶处理、700℃和750℃长期时效以及700℃持久过程中的组织变化规律,并测试了合金室温冲击、拉伸和700℃高温拉伸等力学性能,探讨了组织变化对力学性能的影响。H282合金热处理为固溶+二次时效处理,固溶温度对合金的最终性能影响较大。因此文中主要对合金的固溶处理工艺进行实验选择。随着固溶温度的升高,H282合金中未溶碳化物含量、尺寸均减小,力学性能逐渐降低。最终确定H282合金的最佳热处理制度为1120℃/2h/AC+1010℃/2h/AC+788℃/8h/AC。H282合金700℃、750℃时效态主要析出相为M23C6相、MC相、γ'相。M23C6相富Cr、Mo元素,主要沿晶界分布,少量分布在晶内及孪晶端。随时效时间的延长,M23C6相含量逐渐增加,晶界M23C6相粗化长大呈连续的链状,且750℃变化较快。MC相主要分布在晶内,为富Ti、Mo的一次相,呈块状,尺寸较大。700℃长期时效过程中,组成元素变化较小,750℃时效时形态和成分有所变化。丫'相是合金的主要强化相,含量较高,主要成分为Ni、Al、Ti,750℃5000h时析出量约为18.9%。γ'相的粗化长大规律符合Ostwald熟化机制,根据γ'相颗粒尺寸得到其在700℃、750℃的动力学长大方程。表明700℃时效时,γ'相长大缓慢,时效温度升高,长大速率加快。700℃、750℃时效过程中,合金力学性能变化趋势相同。时效后,冲击功迅速下降,硬度迅速升高。随时效时间的延长,冲击功和硬度变化趋于稳定。这是因为,时效后晶界碳化物连续分布,成为裂纹形成和扩展的通道,弱化晶界,造成冲击功下降,同时γ'相的析出强化作用明显,硬度迅速上升,时效时间延长,丫'相粗化长大,强化作用降低,硬度增加趋势变缓。持久强度是衡量H282合金能否作为700℃先进超超临界火电机组汽轮机转子材料的重要标准,因此对合金进行700℃持久实验。实验结果表明H282合金持久强度较高,700℃10万小时外推强度大于100MPa,满足合金设计要求。微观组织分析发现应力的施加对γ'相形貌、分布无较大影响,对M23C6相形貌有一定影响。持久过程中裂纹主要在晶界形核产生,并沿着晶界碳化物扩展,造成合金断裂失效。
[Abstract]:Haynes282 alloy is aging strengthened nickel based superalloy, due to creep of high strength, high temperature stability and good heat organization, good processing performance, and was selected as the 700 C Advanced ultra supercritical thermal power unit steam turbine rotor of steam turbine rotor material. The material requirements of high strength, high at 700 DEG C tissue stability, oxidation resistance and weldability, in order to ensure the service life of Haynes282 alloy at 700 DEG C steam parameters, on the 700 C or higher temperature under different stress and long-term aging microstructure evolution and mechanical properties in the process of lasting energy change is particularly important. Experimental study on the solid solution treatment, microstructure evolution and 700 C 750 C and 700 C long term aging process, and test the impact and tensile alloy at room temperature, 700 degrees high temperature tensile mechanical properties, discusses the impact of organizational change on the mechanical properties. Heat treatment for H282 alloy solid solution + two aging treatment, solid solution temperature on the final properties of alloy influence. Therefore this paper focuses on the alloy process experiment. With the increase of the solution temperature of undissolved carbide content in H282 alloy, the size decreased, the mechanical properties decreased gradually. Finally the optimum heat treatment system of H282 alloy is 1120 DEG /2h/AC+1010 DEG /2h/AC+788 DEG /8h/AC.H282 alloy 700 DEG, 750 DEG C aging precipitates of M23C6 main phase, MC phase,.M23C6 phase gamma 'rich Cr, Mo elements, mainly distributed along the grain boundaries, a small amount of the distribution in the grain and twin side. As the aging time prolonged the content of M23C6 phase increases gradually, the grain boundary of M23C6 phase coarsening in a continuous chain, and 750 C.MC rapid change is mainly in the grain, is rich in Ti, Mo a, a massive, large size.700 C long-term aging process, elements of change Small changes in morphology and composition of 750 ageing. Y 'phase alloy is the main strengthening phase, higher content of major components of Ni, Al, Ti, 5000h 750 degrees when the precipitation amount is about the coarsening phase of 18.9%. gamma' growth Ostwald mechanism, according to the size of the particles' gamma at 700 degrees, 750 degrees dynamic growth equation. That 700 ageing, y 'growth is slow, aging temperature increasing, the growth rate accelerated.700 C, 750 C in the aging process, changes in mechanical properties of the alloy after aging. The same trend, the impact energy decreased rapidly, the hardness increases rapidly. With the prolonging of aging time. The impact of changes in the work and the hardness tends to be stable. This is because the aging of grain boundary carbide continuous distribution channels become, crack formation and expansion of the weakening of grain boundaries, the impact of power down, while gamma' phase precipitation strengthening effect is obvious, the hardness of the rapid rise in the aging time, ah. Coarsening, strengthening effect decreased, hardness increased gradually slows down. Lasting strength is a measure of H282 alloy can be used as 700 C Advanced ultra supercritical thermal power unit steam turbine rotor material standard, so the 700 C lasting experiment was carried out on the alloy. The experimental results show that the H282 alloy with high strength and lasting 100 thousand hours, 700 C extrapolation strength greater than 100MPa, to meet the design requirements. The alloy microstructure analysis found that applied to gamma 'morphology stress, influence the distribution, has a certain effect on the M23C6 morphology. In the process of persistent crack mainly in grain boundary nucleation, and along the grain boundary carbide expansion caused by alloy fracture failure.

【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG132.3

【引证文献】