Microstructural characterisation and hardness assessment of wire arc cladded Hastelloy C276 on creep resistant steel P91

Abstract

A new structure with nickel-based Hastelloy C276 alloy cladding on creep resistant steel P91 was developed in this study for nuclear applications. The microstructure, including precipitation and grain size, boundaries, orientation and hardness distribution of cladding structures with/without post heat treatment were explored using a range of microscopy techniques and hardness testing. The results show that the as-cladded structure exhibits highly hierarchical heterogeneity, which is mainly related to the remarkably coarse-grained microstructure in the heat-affected zone on the steel side, and typically columnar dendrites formed on the Hastelloy side. After tempering heat treatment, the specimen exhibits re-orientated grains and homogenized microstructure. Meanwhile, the ratio of high angle grain boundaries (HAGBs) in steel regions significantly increases, and the hardness values turn even distribution. This study achieves a sound metallurgical bonding between two structural materials and offers insights into the development of dissimilar metal components with in-site specific properties.

Keywords

• Steel-nickel metal cladding
• Interface
• Grain features
• Microhardness