Manufacture of near-net shape titanium alloy articles from metal powders by sintering at variable pressure

Abstract

The process includes (a) mixing a titanium hydride powder having a particle size of ≦150 μm with alloying metal powders (master alloys or elemental metal powders) having a particle size in the range of {fraction (1/15)}-⅖ of the maximal particle size of titanium hydride powder, (b) compacting the resulting powder mixture by molding at the pressures of 400-1000 MPa, (c) heating up to the sintering temperature of the predetermined alloy composition at variable pressures in a furnace chamber: initial heating to 400° C. in vacuum of less than 10 −2 Pa, then, heating to a temperature range of 400-900° C. with the pressures up to 10 4 Pa, which is controlled by hydrogen being emitted by the decomposition of titanium hydride contained in the compacted powdered alloy, and finally, heating to over 900° C. to the sintering temperature at the pressure continually decreasing to the starting vacuum level, and (d) sintering. Heating to the sintering temperature is performed at the rate of 10-15 grad/min. The new technology allows the purity and mechanical properties of sintered titanium alloys and the manufacture of near-net shape sintered titanium articles to be controlled by a cost-effective method.

We claim:  
     
         1 . The manufacture of near-net shape titanium alloy articles includes: 
 (e) mixing a titanium hydride powder having a particle size of <150 μm with alloying metal powders (master alloys and/or elemental powders) having particle sizes in the range of {fraction (1/15)}-⅖ of the maximal particle size of said titanium hydride powder,    (f) compacting the obtained powder mixture by molding at the pressure of 400-1000 MPa,    (g) heating to the sintering temperature of the predetermined alloy composition at variable pressures in the furnace chamber: initially heating to 400° C. in vacuum of less than 10 −2  Pa, then, heating in a range of 400-900° C. at pressure up to 10 4  Pa controlled by hydrogen being emitted due to the decomposition of titanium hydride contained in the compacted powdered alloy, and finally, heating to over 900° C. to the sintering temperature at the pressure continually decreasing to the starting vacuum level, and,    (h) sintering.    
     
     
         2 . The manufacture of near-shape titanium alloy articles according to  claim 1 , wherein the heating to the sintering temperature is performed with the rate of 10-15 grad/min.