Continuous in situ functionally graded silicon nitride materials

Functionally graded materials can enhance the performance of components under demanding operating conditions, although the development of residual stresses across the gradient and scaling up the manufacturing process to mass production present some limitations. To overcome these problems, we present a one-step approach for processing continuous functionally graded silicon nitride (Si3N4) materials from a sole homogeneous powder composition, using spark plasma sintering as a densification technique. Through the control of the temperature profile within the compact, specimens with a continuous variation of α- and β-phase content, as well as grain size, were achieved. A continuous gradation of mechanical properties, in particular, hardness and toughness, were measured in these specimens. This approach offers unprecedented opportunities to design custom-made Si3N4 components by taking advantage of the particularities of field-assisted sintering methods.