Prakt. Met. Sonderband 38 (2006) 241 
/ of fcc 3 um, respectively, and subsequent polishing using aqueous diamond suspension 
ce the (MD-Chem OPS). 
dmetal Morphological parameters such as average grain size, binder mean free path, and volume 
eferred fraction were determined by quantitative image analyses techniques based on automatic 
iced by and semi-automatic digital image evaluation with a software commercially available. SEM 
of the cross-section micrographs were randomly taken of several gauge areas of the bulk of 
ed e.g. selected specimens. Due to the irregular shape of the particles, we considered the Ferret 
1 strain diameter as a measure of the maximum length of all phases. The volume fraction for each 
of the constituent is given by their area fraction V, = A, according to [14]. 
/ide an Cross-section samples for transmission electron microscopy (TEM) investigations were 
nitrided prepared using a sandwich technique. The samples were cut into two pieces and glued 
e most face-to-face using an epoxy resin (Araldite). Slices of about 0.4 mm in thickness were cut 
sed to from the samples using a wheel cutting machine. Further thinning was carried out by 
mechanical polishing (diamond lapping-film) and dimple grinding with 1um disc down to a 
Thus, sample thickness of about 20 pum. Finally, the specimens were thinned to electron 
of the transparency by Ar’ ion milling in a precision ion polishing system (PIPS) with main 
ides in parameters such as tension and current set at 4 keV and 16 mA, respectively. 
, grain TEM/STEM in combination with energy dispersive X-ray analysis (EDX) was employed in 
> of the order to determine the elements that diffused from the hard phases e.g. Ti and W and 
re and dissolved in the metallic matrix. The size of the hard phases in the nitrided layer was 
rnative determined from TEM micrographs. 
> could a 
Sample Approximate composition Binder Treatment Thickness of fcc- 
d by a P (Wt. %) (wt. %) rich layer 
binder A 60WC-30(Ti, Ta,Nb)C-10Co 100% Co 
ly B 60WC-30(Ti,Ta,Nb)C-10Co 100% Co N, 8.0 um 
M/EDX ; 60WC-30(Ti,Ta,Nb)C-10Ni 100% Ni 
I. 60WC-30(Ti,Ta,Nb)C-10Ni 100% Ni r 4.0 um 
E 60WC-30(Ti,Ta,Nb)C-10(Co+Ni) 50% Co+50% Ni 
F 60WC-30(Ti, Ta,Nb)C-10(Co+Ni) 50% Co+50% Ni N; 6.0 um 
G 60WC-30(Ti,Ta,Nb)C-10(Co+Ni) 50% Co+50% Fe 
H 60WC-30(Ti,Ta,Nb)C-10(Co+Ni) 50% Co+50% Fe N, 27.0 um 
S0OWC-30(Ti,Ta,Nb)C-10(Co+Ni) 50% Ni+50% Fe 
J 60WC-30(Ti,Ta,Nb)C-10(Co+Ni) 50% Ni+50% Fe N2 14.0 um 
eA Table 1. Composition, sintering conditions of the samples. and average thickness of the outer-surface layer. 
mm, 
phase 
s were 3. RESULTS AND DISCUSSION 
ding to 
/olume 3.1 Microstructure of non-nitrided hardmetals 
The bulk microstructure of the non-nitrided hardmetal samples A, C, E, G, and | (Table 1) 
is characterized by a homogeneous distribution of prismatic WC and rounded y-phase 
grains embedded in the various matrices studied (Fig.1). Quantitative image analyses 
lectron showed that the binder system does not affect the binder mean free path and the average 
: SEM grain size of the hard phases in the bulk (Table 2). The distribution of values of binder 
3 ere mean free path is characterized by a broad dispersion around the average value. 
m an