Effect of Post-Fabrication Heat Treatments on the Microstructure of WC-12Co Direct Energy Depositions

Abstract

Laser-Directed Energy Deposition (L-DED) is an additive manufacturing technique that has lately been employed to deposit coatings of cemented carbides, such as WC-Co. During deposition, complex microstructural phenomena usually occur, strongly affecting the microstructural and mechanical behavior of the coatings. Post-fabrication heat treatments (PFHTs) may be applied to homogenize and strengthen the microstructure; nevertheless, to the best of the authors’ knowledge, just a few papers deepened the effect of these treatments on cemented carbides fabricated by additive manufacturing. This work evaluates the influence of four PFHTs on the microstructural evolution and hardness of L-DED WC-12Co. For each treatment, different combinations of solubilization time and temperature (between 30 and 180 min and from 400 °C to 700 °C, respectively) were adopted. The microstructure was investigated by optical and scanning electron microscopy equipped with energy-dispersive spectroscopy, whereas the mechanical properties were determined by Vickers hardness measurements. Based on the results, high microstructural heterogeneity in terms of WC particles, η-phase structures, and Co distribution was observed in the sample in the as-built condition. Some cracking defects were also observed in the samples, irrespective of the heat treatment conditions. Finally, a finer microstructure and a lower amount of brittle ternary η-phase, together with an increase in hardness (1030 ± 95 HV10), were found for the highest dwelling times (180 min) and for solubilization temperatures in the range of 500–600 °C.

Evaluation of Austenitic Stainless Steel ER308 Coating on H13 Tool Steel by Robotic GMAW Process

“…Various surface modification processes are used, depending on the specific end application. These processes may include welding arc technologies such as gas metal arc welding (GMAW) [19], gas tungsten arc welding (GTAW) [20], cold metal transfer (CMT) [21,22], plasma transferred arc (PTA) [22,23], and high-energy processes such as laser technologies [24][25][26] or additive manufacturing (AM) [27,28].…”