Microstructural development and solidification cracking susceptibility of Cu deposits on steel: Part II—use of a Ni interlayer

The tool and die industry is interested in depositing Cu onto steel using direct metal deposition techniques in order to improve thermal management of mold dies manufactured from steel alloys. However, Cu is a known promoter of solidification cracking in steel. Ni, however, is known to improve weldability of Cu containing alloys and steel. The goal of this work was to identify the range of Ni concentrations necessary to eliminate solidification cracking in Steel–Cu deposits and understand the cracking susceptibility through analysis and modeling of microstructural development. A wide range of Steel–Ni–Cu deposits, containing up to 75 wt% Ni, and Ni–Cu deposits were fabricated using the Gas Tungsten Arc Welding (GTAW) process with cold wire feed. The Ni–Cu and Fe–Ni deposits were found to be crack free over the entire concentration range. However, Ni concentrations of up to 75 wt% were insufficient to eliminate cracking when subsequent layers of Cu were deposited. Therefore, to ensure crack free deposition of Cu onto Steel, the concentration of the interlayer must be 100 wt% Ni. The resultant microstructures were characterized by various microscopy techniques to understand the influence of Ni and Cu on solidification cracking of Steel. Additionally, solidification modeling was undertaken to determine the amount of terminal Cu rich liquid and solidification temperature range that would form under non-equilibrium solidification conditions.