PSI - Issue 36

Ihor Koval et al. / Procedia Structural Integrity 36 (2022) 51–58 Ihor Koval et al. / Structural Integrity Procedia 00 (2021) 000 – 000

54 4

microstructures of alloys 1-4 with the indicated research spectra in different structures elements, the EDS spectrum results in binder and line distribution are presented. Chemical composition of structure elements is shown in Tables 2-5. In alloy 1 (10% (wt.) binder), containing 7.5% wt. of nano Ni, the microstructure consists mainly of small carbide grains with a core/rim structure, most core being of the triangular or rectangular shapes, similar to that of carbide grains formed in alloys based on tungsten carbide. As it is shown by Brieseck (2010), in tungsten carbide-based alloys, the grains of triangular and rectangular shape have sizes being in 1.5…3 times larger than those of polygonal shape and by 1.9 GPa lower microhardness. Thus, in the studied alloys the microstructure of the maximum polygonal shape, up to the rounded one, is needed to be obtained.

Fig. 2. SEM image alloy 1 (a) with spectrum points, line distribution, EDS result in binder (b).

Table 2. Chemical composition of structure elements in alloy 1.

Core

Rim

Binder

Homogeneous carbide grain

Element

wt%

at%

wt%

at%

wt% 8.08

at%

wt%

at%

C

19.60 50.83 17.27 51.60

29.85

12.86 50.71

41.19 40.73

Ti Cr Ni

71.12 46.24 50.50 37.84 14.47 13.41

1.52 0.78 2.58 4.41

0.91 0.41 0.86 0.75

1.74 3.31

1.20 2.02 4.10 3.23

12.06 10.29 58.69 44.36

3.96

2.93

15.64

10.25

Nb

10.62 16.56

1.98 4.73

0.95 1.14

6.70

2.77 2.12

W

10.13

As it is seen on the Table 2, not only a significant amount of niobium, tungsten is concentrated in the rim, but also binder metals, which form with titanium a complex solid solution (Ti,Nb,W,Ni,Cr)C, being treated as the barrier at the diffusion of nickel and chromium into the carbide grain and the reverse diffusion of carbide metals in binder