Haynes282耐热合金铸态组织及锻后析出相研究

RESEARCH ON AS-CAST MICROSTRUCTURE AND PRECIPITATION AFTER FORGING OF HAYNES282 HEAT-RESISTING ALLOY

Haynes282合金是700℃超超临界发电机组高温段转子和气缸等构件的首选材料。Haynes282合金铸件组织控制和锻件析出相调控,是相关产品生产工艺制定的难点。以Haynes282为研究对象,通过金相、SEM、EDS等方法,对Haynes282合金电渣重熔后的铸态组织以及锻造后的析出相特性进行系统表征。结果表明,Haynes282合金的枝晶尺寸对冷速非常敏感;电渣锭心部的二次枝晶臂间距要大于表层的,分别为72μm和56μm。枝晶臂和枝晶间元素Al、Cr、Co的偏析系数接近1,元素Mo和Ti的偏析系数较大,Ti的偏析系数超过了1. 7;铸锭心部的偏析比表层略大。经过1 150℃均匀化8 h的热处理和锻造,基本消除了合金中的元素偏析;锻后在晶界上断续分布的第二相主要为富Mo和Cr的M_(23)C_6。

Haynes282 alloy is the preferred material for components such as rotor and cylinder in high temperature section of 700 ℃ ultra-supercritical generating set.Microstructure control of Haynes282 alloy casting and precipitation phase control of forgings are the difficulties in the production process of related products.The as-cast structure and precipitated phase characteristics of Haynes282 alloy after ESR were systematically characterized by metallography,SEM and EDS.The results show that the dendrite size of Haynes282 alloy is very sensitive to the cooling rate,and the secondary dendrite arm spacing in the core of electroslag ingot is larger than that in the surface layer,which is 72 and 56 μ m,respectively.The segregation coefficients of dendritic arm and interdendritic elements Al,Cr and Co are close to 1.The segregation coefficients of Mo and Ti are larger,the latter is more than 1.7.The center segregation coefficients of ingot is slightly larger than that in the surface.The elements segregation in the alloy was basically eliminated by heat treatment and forging at 1 150 ℃for 8 hours,and the second phase distributed intermittently on the grain boundary after forging was mainly M23C6 with rich Mo and Cr.