MICROSEGREGATION AND SOLIDIFICATION CRACKING OF AN HR-160 WELD OVERLAY

The solidification behaviour (microsegregation, secondary phase format ion, solidification temperature range) of a Haynes HR-160 weld overlay deposited on 2.25 Cr-IMo steel by gas metal arc welding has been exam ined. Results of differential thermal analysis and various microscopy techniques conducted on an all-weld-metal sample indicate the overlay terminates solidification at approximate to 1290 degrees C by the form ation of a (Ti-S)-rich second phase distributed semi-continuously alon g grain boundaries. The semi-continuous morphology of the second phase , combined with an increase in the solidification temperature range in duced by the second phase, promoted solidification cracking in the ove rlay deposit. Electron probe microanalysis (EPMA) was used to reveal p atterns of elemental segregation within the weld overlay. The EPMA dat a was used with basic solidification theory to estimate values for equ ilibrium distribution coefficients of major alloying elements and the values are found to be similar to results previously reported for Inco loy 909.