Microstructure and hardness evolution of ERNiCrMo-3 deposited metal during aging at 750 °C

The microstructure and hardness evolution of ERNiCrMo-3 deposited metal exposed at 750 degrees C have been investigated in this study. In the as-welded sample, the MC/TiN, Laves, and delta phase can be found in the interdendritic regions, but only MC/TiN phase located at the grain boundaries. After the aging treatment, additional M23C6 carbides can be observed at the grain boundaries and nanosized gamma '' particles formed in the matrix. Both delta phase and gamma '' phase were found to possess one certain orientation relationship and semi-coherent interfaces with the matrix, which are responsible for the hardening of the deposited metal during the initial stage of aging. With the increase in aging time from 10 to 100 h, gamma '' phase coarsens, but needle-like delta phase becomes denser and longer, which contributes to the successive hardening.

Automated summary

The study found that delta phase and gamma'' phase in ERNiCrMo-3 deposited metal have certain orientation relationships and semi-coherent interfaces with the matrix, leading to hardening during the initial aging stage. As aging time increases from 10 to 100 hours, gamma'' phase coarsens while needle-like delta phase becomes denser and longer, contributing to continuous hardening.