Creep behaviour and microstructure evolution in Super 304H–P92 heterogeneous welds

ABSTRACT

The paper deals with results of long-term stress rupture tests on “cross-weld“ specimens made of Super 304 H – P92 heterogeneous welds. Stress rupture tests were carried out at temperatures of 625°C and 650°C up to 20,000 hours to rupture. Creep rupture strength and WSF values of Super 304 H – P92 welds for 10,000 hours at both 625°C and 650°C were calculated. The preferential location of failure was the intercritical part of the heat affected zone in P92 steel. Hardness of both base materials did not show significant changes during creep exposure at both 625°C and 650°C. However, gradual hardening of the weld metal occurred. Metallographic studies were performed in individual parts of heterogeneous welds. A special attention was paid to precipitation reactions in both base materials and heat affected zones. A residual content of vanadium in Super 304 H steel affected precipitation processes. Vanadium partly substituted niobium in the modified Z-phase ((V,Nb)CrN).

KEYWORDS:

• Heterogeneous welds
• stress rupture tests
• creep rupture strength
• heat affected zones
• microstructure evolution
• minor phases
• modified Z-phase

Acknowledgments

This paper was supported by the TACR agency under Grant “TK03020055 Research on creep behaviour and verification of brittle-fracture properties of austenitic steels for thermal power plant blocks with USC steam parameters” and by the Student grant competition project “SP2023/049 The influence of production parameters and operating conditions on the microstructure and utility properties of metallic materials”. R.P. gives thanks for financial support from the project no. 00424/2022/RRC funded by the Moravian-Silesian Region “Support for gifted students of doctoral studies at VŠB-TUO”.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Moravian-Silesian Region, Czech Republic [00424/2022/RRC]; Technology Agency of the Czech Republic [TK03020055]; Vysoká Škola Bánská - Technická Univerzita Ostrava [SP2023/049].