Metallurgical and Materials Transactions A

, Volume 26, Issue 5, pp 1273–1286 | Cite as

Influence of heat treatments on microstructure, mechanical properties, and corrosion resistance of weld alloy 625

  • F. Cortial
  • J. M. Corrieu
  • C. Vernot-Loier
Welding and Joining


The effects of heat treatments of the industrial type (eight-hour hold times at temperatures between 600 °C and 1000 °C) on the structural, mechanical, and corrosion resistance characteristics of weld alloy 625 have been studied. During the heat treatment, the mean concentration ratios of Nb, Mo, Si, Cr, Ni, and Fe elements between the interdendritic spaces and dendrite cores show little evolution up to 850 °C. Beyond that temperature, this ratio approximates 1, and the composition heterogeneity has practically disappeared at 1000 °C. An eight-hour heat treatment at temperatures between 650 °C and 750 °C results in increased mechanical strength values and reduced ductility and impact strength linked to the precipitation of body-centered tetragonal metastable intermetallic γ″ Ni3Nb phase in the interdendritic spaces. An eight-hour treatment in the temperature range between 750 °C and 950 °C has catastrophic effects on all mechanical characteristics in relation with the precipitation, in the interdendritic spaces, of the stable orthorhombic intermetallic δ Ni3(Nb, Mo, Cr, Fe, Ti) phase. At 1000 °C, the ductility and impact strength are restored. However, the higher the heat treatment temperature, the weaker the mechanical strength. Heat treatments have no effect on the pitting resistance of weld alloy 625 in sea water. The comparison of the results of this study on weld alloy 625 with those previously obtained on forged metal 625 shows that heat treatments below 650 °C and above 1000 °C are the sole treatments to avoid embrittlement and impairment of the corrosion resistance characteristics of alloy 625.


Material Transaction Weld Metal Impact Strength Heat Treatment Temperature Lave Phase 


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Copyright information

© The Minerals, Metals & Material Society 1995

Authors and Affiliations

  • F. Cortial
    • 1
  • J. M. Corrieu
    • 1
  • C. Vernot-Loier
    • 1
  1. 1.Centre d’Etude des Structures et Matériaux NavalsDGA/DCN INDRETLa MontagneFrance

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