246 Prakt. Met. Sonderband 38 (2006) 
composition on the corrosion behavior of hardmetals [1-5,11], this result suggests that the Mi 
higher corrosion resistance observed in Ni-binder hardmetals compared to the Co-binder HY 
is not only due to the higher redox potential of Ni but it is further enhanced by the higher 
amount of W and Ta present in Ni. Cutting tests to evaluate the performance of the HF 
investigated hardmetals are currently being performed. ; 
4. SUMMARY 
We investigated the effect of both binder composition and a nitridation surface treatment AB 
on the microstructure of (W,Ti)C-(Ta,Nb)-based hardmetals. The characteristics of Th 
see : . . e 
diffusion surface layers in hardmetals may be controlled by an appropriate choice of tech 
binder. The main conclusions are: Las 
e the binder metal does not affect the binder mean free path and the grain size micı 
distribution of the hard phases within the bulk; only 
e the thickness of the surface layer is strongly affected by the binder composition; seg) 
e the nitridation treatment does not affect the chemical composition of the binder; Cry: 
e round-edged WC grains may be obtained by a suitable selection of the binder system, dire 
which could improve toughness and increase resistance to cracking propagation. sligt 
e The amount of dissolved elements from the hard phases in the binder can be 
increased by the substitution of the binder metal. 1. 1 
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