Binder Jet Printing of a Low-Cost Tool Steel Powder

Abstract

Water atomization is a commonly used process to inexpensively produce large volumes of powders for press-and-sinter powder metallurgy. While the resulting powder particles are typically irregularly shaped and relatively coarse, adjustments to the atomization parameters can yield particles that are finer in size and nominally spherical, thereby facilitating their potential for application in additive manufacturing (AM). Thus, the objective of this research was to investigate the viability of water atomized D2 tool steel powder in the context of binder jet printing (BJP). Builds were printed, cured, de-bound, and sintered under various conditions to assess densification behaviour. Optimal sintering conditions for maximum density (98.5% theoretical) without significant distortion or grain coarsening were determined to be 1250°C for 30 min under high vacuum. Printed samples underwent a standard heat treatment process for wrought D2 and performed comparably to the wrought counterpart. Heat-treated BJP samples retained key microstructural features imparted by the printing process such as carbide clusters within large grains and intergranular lamellae of eutectic carbides and prior austenite, whereas the wrought microstructure was largely homogenous with fine grains and carbides.