Structural phase evolution with temperature of non-conventional particles in PIM

Some inorganic natural powders may be interesting to manufacture complex shapes by powder injection moulding (PIM). However, these powders may evolve chemical and physically with temperature during the manufacturing processes, inducing blusters and geometrical irregularities, particularly loss of circularity. These imperfections were associated to gas liberation and dimensional variations during the debinding and sintering treatments and not to feedstocks’ fluidity. Natural powders for manufacturing products by PIM must be previously calcined before conformation, in order to eliminate possible chemical reactions and phase transformation during debinding and sintering. To highlight the effect of the calcination process in the final quality of the sinter, a complex geometrical testing-probe was developed. After sintering, calcined and non-calcined powders have similar mechanical properties (σ0calcined=111 MPa, σ0non-calcined=93 MPa, Weibull modulus = 10). The use of a feedstock of the natural calcined powders leads to PIM products with high geometrical reproducibility and good surface finishing.