NbC-BASED CERMET PRODUCTION COMPARISON: L-PBF ADDITIVE MANUFACTURING VERSUS CONVENTIONAL LPS POWDER METALLURGY

Abstract

The production of carbide parts (cermet) by additive manufacturing, such as laser powder bed fusion (L-PBF), has been a great challenge due to the complex optimization of process parameters to improve density, porosity, microcracks or abnormal growth of grains and obtain a microstructure as homogeneous as possible. This work aims to compare the evolution of the microstructure when using the conventional route of powder metallurgy, i.e., liquid phase sintering (LPS) with the L-PBF direct additive manufacturing process, considering the NbC-based carbide material. Sample compositions were prepared in w/%, samples were compacted under 50–125 MPa, without polymeric binders, and they were sintered under a vacuum at temperatures of 1330 °C and 1370 °C. For the L-PBF process, a vibrating device made it possible to improve the fluidity of the mixtures of three alloys, NbC–30Co, NbC–30Ni and NbC–30(Co, Ni). The mixtures exhibited low sphericity, low fluidity and compressibility, which were improved with a roller compactor. Thin powder mixture deposition layers were evenly applied and well distributed across the powder bed to avoid defects and cracks during sintering. The L-PBF process parameters varied including a power of 50–125 W and a laser scanning speed of 25–125 mm·s–1. Different microstructures, identified with a light microscope (LM) and a scanning electron microscope (SEM), and properties obtained with the two processes, direct (L–PBF) and indirect sintering (LPS), were compared.