The preparation of TiC dispersion strengthened tungsten alloy via freeze-drying method

Abstract

First time, TiC dispersion strengthened tungsten powder was prepared by freeze-drying method. The aqueous solution containing dispersant (Polyvinyl Pyrrolidone (PVP)+ Methacrylic Acid (MA)), ammonium metatungstate (AMT) and TiC particles was sprayed into liquid nitrogen. After vacuum drying, the amorphous precursor powder was obtained. Rapid cooling and vacuum drying made precursors have unique fishbone like porous structure. After calcining and reduction, the W-TiC powder was obtained. The W-TiC powder made by freeze-drying method had small size, near-spherical appearance and well chemical activity. After being sintered by spark plasma sintering (SPS), small size sintered W-0.2/1.0(wt%) TiC alloys with significantly improved mechanical properties were obtained. The microstructure and fracture surface of the W-TiC alloys showed that TiC particles were evenly distributed in the grain interiors and boundaries. With the TiC content increasing to 1%, no obvious particle agglomeration was detected. Uniformity of TiC dispersion was attributed to the combination of dispersant (PVP + MA) and rapid cooling. Based on the successful preparation of small sintered samples, 1.0 kg W-0.2TiC powder was prepared to verify the possibility of mass production by the same method. After medium frequency induction sintering and hot rolling, W-0.2TiC plate with 60% deformation was successfully prepared. Obtained W-0.2TiC plate had strength of more than 1700 MPa and a ductile brittle transition temperature (DBTT) of about 200 °C.