Method of making agglomerated cemented carbide powder mixtures
The present invention relates to a method of making an agglomerated powder mixture by wet milling a powder mixture containing hard constituent powder(s) based on carbides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and/or W and greater than about 15 wt-% binder phase powder(s) of Co and/or Ni as well as pressing agents and spray drying said slurry. By adding to said powder mixture before milling in addition from about 0.05 to about 0.50 wt-% of a complex forming and/or pH-decreasing/increasing additive such as triethanolamine, hydroxides or acids and a thickener in an amount of from about 0.01 to about 0.10 wt-% agglomerates with excellent flow properties are obtained.
1. Method of making an agglomerated powder mixture comprising:
forming a slurry by wet milling a powder mixture containing hard constituent powder(s) based on carbides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and/or W and greater than about 15 wt-% binder phase powder(s) of Co and/or Ni as well as pressing agents and adding to said powder mixture before milling additionally from about 0.05 to about 0.50 wt-% of triethanolamine and a thickener in an amount of from about 0.01 to about 0.10 wt-%; and
drying said slurry to form the agglomerated powder mixture.
2. A method claim 1 wherein said thickener is one or more of cross-bonded acrylate emulsions, hydrophobic modified-hydroxyethyl cellulose (HM-HEC), hydrophobic modified-ethyleneoxide-urethane (HEUR), styrene-maleic anhydride copolymers, xanthan polysaccharide and ethylhydroxyethyl cellulose (EHEC), alone or in combination.
3. A method of claim 1 wherein said powder mixture contains from about 20 to about 30 wt-% binder phase powders.
4. A method of claim 1 wherein said hard constituent comprises WC.
5. A method of claim 1 wherein drying is by spray drying.
6. A method of claim 1 wherein the agglomerated powder mixture has an agglomerate size distribution with a span, S=d97/d03<1.2, where d97=the agglomerate size below which 97% of the agglomerates is found and d03=the agglomerate size below which 3% of the agglomerates is found.