微观组织调控提高GH3625合金管材在高温KCl-MgCl2熔盐环境下的耐腐蚀性能

Corrosion Resistance Enhancement of GH3625 Alloy Tube in High-Temperature KCl-MgCl2 Molten Salt Environment via Microstructure Tailoring

摘要:

采用EBSD、XRD、SEM和EDS等手段研究了含不同比例孪晶的微观组织对GH3625合金管材在高温（600~800 ℃）KCl-MgCl₂熔盐中腐蚀行为的影响。结果表明，随着退火温度的升高，GH3625合金管材等轴晶组织中退火孪晶界的比例增加，且在相同腐蚀温度下合金中孪晶界比例越高，其耐高温KCl-MgCl₂熔盐腐蚀性能越好；同时，随着腐蚀温度的升高，同一组试样的耐高温KCl-MgCl₂熔盐腐蚀性越差。此外，在晶粒尺寸相同的条件下，GH3625合金管材中退火孪晶界比例越高，其耐高温KCl-MgCl₂熔盐腐蚀性能也越好，这主要归因于高密度稳定的退火孪晶界本身具有优异的抗腐蚀能力以及包含孪晶界的三叉晶界打断了原有大角度晶界网络的连通性，抑制了晶界的腐蚀。

Abstract:

The effect of microstructure with different twin boundary fraction on the corrosion behavior of GH3625 alloy tube in high-temperature (600–800 ℃) KCl-MgCl₂ molten salt was investigated using EBSD, XRD, SEM, and EDS. The results show that with the increase in annealing temperature, the proportion of annealing twin boundaries in the equiaxed grains of GH3625 alloy tube is increased. Consequently, the higher the proportion of twin boundaries in the alloy at the same corrosion temperature, the better its high-temperature resistance to KCl-MgCl₂ molten salt corrosion. Furthermore, as the temperature increases, the corrosion resistance of a given set of samples to KCl-MgCl₂ molten salt deteriorates. In addition, at a constant grain size, an increased fraction of annealing twin boundaries correlates with enhanced corrosion resistance of GH3625 alloy tubes in KCl-MgCl₂ molten salt at high temperature. This is mainly attributed to the excellent intrinsic corrosion resistance of high-density stable annealing twin boundaries, coupled with the fact that the triple junction containing twin boundaries breaks the connectivity of the original high-angle grain boundary network, thereby suppressing the corrosion of the grain boundaries.