Effect of hot isostatic pressing on porosity of wire-arc directed energy deposited TZM/NbZr1 bimetallic structure

This study examined the effectiveness of hot isostatic pressing (HIP) in reducing porosity in TZM-NbZr1 bimetallic structures produced via wire-arc directed energy deposition (DED). Different HIP conditions and a combined HIP and heat treatment (HT) were evaluated. Porosity decreased from 4% in the as-built state to 3.05% at 1200°C and 1% at 1500°C, with further reduction to 0.01% after HIP at 1800°C followed by HT. Plastic deformation influenced pore size and shape, with lower temperatures causing micro-cracks, while the combined HIP and HT process eliminated cracks and porosity through dynamic recrystallization. Higher temperatures also promoted Mo diffusion from TZM to NbZr1.