GB966776A - Refractory compacts and their manufacture - Google Patents

Abstract

<PICT:0966776/C1/1> Powdered compositions consisting essentially of 20-53% Si, 40-65% Mo, 1-19% N, and 5-20% ZrO2, ZnO or Cr2O3 are used to manufacture shaped objects by heating under pressure until a substantially homogeneous sintering and alloying occurs and allowing the so-formed object to cool to room temperature. Starting materials specified are silicon nitride, molybdenum disilicide and elemental molybdenum. Up to 5% of inert diluents, e.g. Al, Mn, Ca, Mg, Cu and Ni may be present as elements or oxides. As described, these starting materials as powders are milled in the presence of benzene (water and 1-5% NaOH are also mentioned), dried and screened. Pre-ground dry ZrO2 is then added and the whole blended to give a mixture having a particle size predominantly of 1-3 micron. Acceptable products are formed where the particle size is up to 75 microns of which 75% are less than 5 microns. Die nibs for hot metal extrusion are manufactured by placing the composition at 16 (Fig. 2), in a bore 9 in a cylindrical graphite mould 10 having a base plate 11 through which a core piece 12 extends, tamping with plunger 17 and placing the assembly in a hydraulic press. 1000 p.s.i. is applied at room temperature and the temperature raised to 1200 DEG C. in 8 minutes thereupon the pressure is raised to 2000 p.s.i. and heating continued to 1600 DEG C. in 5 minutes. The pressure is again raised to 3000 p.s.i., the composition "soaked" for 30 minutes when the temperature is raised to 1650 DEG C. in 1 minute and the pressure to 4000 p.s.i. After 5 minutes the pressure and temperature are discontinued. The shaped objects have high lubricity and toughness and when used in die nibs for extruding metals, no lubricant is required. The composition may be first partly reacted and alloyed, pulverized and then re-sintered to form the desired compact. Specifications 924,414, 966,774 and 966,775 are referred to.ALSO:<PICT:0966776/C6-C7/1> Powdered compositions consisting essentially of 20-53% Si, 40-65% Mo, 1-19% N, and 5-20% ZrO2, ZnO or Cr2O3 are used to manufacture shaped objects by heating under pressure until a substantially homogeneous sintering an alloying occurs and allowing the so formed object to cool to room temperature. Starting materials specified are silicon nitride, molybdenum disilicide and elemental molybdenum. Up to 5% of inert diluents, e.g. Al, Mn, Cr, Mg, Cu and Ni may be present as elements or oxides. As described, these starting materials as powders are milled in the presence of benzene (water and 1-5% NaOH are also mentioned), dried and screened. Pre-ground dry ZrO2 is then added and the whole blended to give a mixture having a particle size predominantly of 1-3 microns. Acceptable products are formed where the particle size is up to 75 microns of which 75% are less than 5 microns. Die nibs for hot metal extrusion are manufactured by placing the composition at 16, Fig. 2, in a bore 9 in a cylindrical graphite mould 10 having a base plate 11 through which a core piece 12 extends, tamping with plunger 17 and placing the assembly in a hydraulic press. 1000 p.s.i. is applied at room temperature and the temperature raised to 1200 DEG C. in 8 minutes thereupon the pressure is raised to 2000 p.s.i. and heating continued to 1600 DEG C. in 5 minutes. The pressure is again raised to 3000 p.s.i., the composition "soaked" for 30 minutes when the temperature is raised to 1650 DEG C. in 1 minute and the pressure to 4000 p.s.i. After 5 minutes the pressure and temperature are discontinued. The shaped objects have high lubricity and toughness and when used in die nibs for extruding metals no lubricant is required. The composition may be first partly reacted and alloyed, pulverized and then resintered to form the desired compact. Specifications 924,414, 966,774 and 966,775 are referred to.