Effect of cyclic loads on fatigue behavior of Ni–Cr–B–Si cladding on 316L(N) SS using PTA process

316L(N) stainless steel (SS) components in Sodium-Cooled Fast Reactors (SFRs) are hardfaced with NiCrBSi alloy in order to avoid self-welding. Hardfacing is performed by the plasma transferred arc welding (PTA) process, as it gives lesser dilution. Cyclic loads are acting at the substrate/cladding interface due to varying thermal expansion coefficients of the two materials. These cyclic loads may lead to fatigue cracking in the cladding. It is very important to study the fatigue characteristics of hardfaced specimens due to these cyclic loads. In the present work, 316L(N) SS is hardfaced with NiCrBSi alloy using the PTA process, and cyclic loads are applied upon the specimens in high cycle fatigue tests at a stress ratio of 0.1 and a frequency of 15 Hz. This work aims to find out the fatigue behavior of the cladding on these specimens. The fatigue limit decreases by 20% for the hardfaced specimens compared to the base metal. There are no fatigue cracks on the cladding up to a cyclic load of 280 MPa, and the cladding remains bonded with the substrate. However, cracks are visible in the cladding for loads above 280 MPa, and debonding is observed. Hardfacing of NiCrBSi on 316L(N) SS by the PTA process is suitable for use where the cyclic stress on SFR components is below 280 MPa.