Enhanced cracking resistance and deposition of alloy 36 via accelerated cooling and TiC addition during wire arc additive manufacturing

The sensitivity of the single-phase, low thermal expansion (LTE) alloy 36 (Fe-36Ni) to intergranular cracking hinders its processability during additive manufacturing. This study investigates the effect of accelerated cooling via a CO2 jet and the addition of TiC particles on the cracking susceptibility of the LTE36 alloy during wire-arc additive manufacturing (WAAM). Results show that accelerated cooling reduces inter-pass deposition times and the susceptibility to cracking due to increased heat dissipation. A crack-free microstructure was achieved only with the addition of TiC particles, which pinned the high-angle grain boundaries and induced tortuosity, thereby limiting grain growth and mitigating intergranular cracking. Mechanical performance was restored compared to the cracked condition, and the critical LTE property of the as-deposited LTE36 alloy was improved due to the enhanced ferromagnetic character of the alloy. Therefore, the combined approach effectively mitigated intergranular cracking while retaining the LTE behaviour during WAAM of the LTE36 alloy.