Method of producing a highly dense semifinished product or component

Abstract

A component or semifinished product is produced of a material of the group comprising molybdenum, molybdenum alloy, tungsten and tungsten alloy with an average relative density of >98.5% and a relative core density of >98.3%. The material is sintered to a relative density D, with 90%<D<98.5% and a proportion of the closed pores with respect to the overall porosity of >0.8 and also hot-isostatically pressed at a temperature 0.40 to 0.65×solidus temperature and under a pressure of from 50 to 300 MPa. Components produced in this way, used for example as electrodes, have much improved service life characteristics.

1 . A method of producing a component or semifinished product from a material of the group comprising molybdenum, molybdenum alloy, tungsten and tungsten alloy with an average relative density of >98.5% and a relative core density of >98.3%, the method which comprises the following steps: 
 preparing a powder with a particle size according to Fisher of from 0.5 to 10 μm;    pressing the powder under a pressure of 100 to 500 MPa;    sintering at a temperature of 0.55 to 0.92 ×solidus temperature, to form a sintered body with relative density D, with 90%<D<98.5%;    hot-isostatic pressing, substantially without utilizing a can, at a temperature of 0.40 to 0.65 ×solidus temperature and under a pressure of 50 to 300 MPa; and forming with a degree of forming φ, with 15%<φ<90%.    
     
     
         2 . The method according to  claim 1 , which comprises forming a component or a semifinished product with an average grain number of >100 grains/mm 2  in a deformed state thereof.  
     
     
         3 . The method according to  claim 1 , prior to hot-isostatic pressing, subjecting the sintered body to additional forming, with a degree of forming of 2%<φ<60%.  
     
     
         4 . The method according to  claim 1 , wherein the sintered body has a proportion of closed pores with respect to an overall porosity of >0.8.  
     
     
         5 . The method according to  claim 1 , which comprises forming a component or a semifinished product of K-doped tungsten (AKS-W) having a K content of 5 to 70 μg/g.  
     
     
         6 . The method according to  claim 1 , wherein the forming step comprises radially forging or rolling to produce a rod.  
     
     
         7 . The method according to  claim 6 , which comprises forming the rod with a diameter of from 15 to 55 mm.  
     
     
         8 . The method according to  claim 6 , which comprises producing a lamp electrode with the rod.  
     
     
         9 . The method according to  claim 8 , which comprises integrating the lamp electrode in a short arc lamp.