Susceptibility to Solidification Cracking in High Chromium Nickel-Base Filler Metals for Nuclear Power Application

This paper presents a comparative study on the solidification behavior and weld solidification cracking susceptibility in a series on high-Cr, Ni-base welding filler metals with nuclear power application. One heat of ERNiCrFe-7A (alloy 52M), three heats of ERNiCrFe-13 (alloy 52MSS), one heat of ERNiCr-3 (alloy 82) ant two heats of ERNiCrFe-15 (alloy 52i) were tested using both the Transvarestraint test and the Cast Pin Tear test (CPTT). The solidification behavior in these filler metals was studied using thermodynamic simulations and a newly developed experimental procedure. The latter accurately replicates solidification process in fusion welds of Ni-base alloys and is based on the patented technique for Single Sensor Differential Thermal Analysis (SS DTA^TM).

It was found that alloy 82 has the widest solidification range, followed by the two heats of alloy 52i, the three heats of alloy 52MSS, and alloy 52M. Alloys 82 and 52i also had the widest eutectic temperature range. The interdendritic eutectic constituent formed in weld metal of alloys 82, 52i, and 52MSS was enriched in Nb and resulted from a eutectic reaction at the end of solidification.

The CPTT ranked the tested alloys from least to most susceptible as follows: 52i-B, 82, 52M, 52i-A, 52MSS-C, 52MSS-B, and 52MSS-A. The Transvarestraint test provided similar ranking with the exception of alloy 52i-B that was found more susceptible than 82 and 52M. No direct correlation was found between the solidification and eutectic temperature ranges of the tested alloys and their solidification cracking susceptibility, Figure 1. Crack healing by liquid backfilling was found in all tested alloys.