The solidification behaviour (microsegregation, secondary phase formation, solidification temperature range) of a Haynes HR-160 weld overlay deposited on 2.25 Cr-IMo steel by gas metal arc welding has been examined. 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 formation of a (Ti-S)-rich second phase distributed semi-continuously along grain boundaries. The semi-continuous morphology of the second phase, combined with an increase in the solidification temperature range induced by the second phase, promoted solidification cracking in the overlay deposit. Electron probe microanalysis (EPMA) was used to reveal patterns of elemental segregation within the weld overlay. The EPMA data was used with basic solidification theory to estimate values for equilibrium distribution coefficients of major alloying elements and the values are found to be similar to results previously reported for Incoloy 909.