Effect of mechanical activation of WC-based powder on the properties of sintered alloys

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 23 No. 1 2021 a b Fig. 4. CDD size ( a ) and microdistortion ( b ) calculated for WC phase depending on the milling time Figure 5 shows X-ray images of sintered samples. It can be seen that in all alloys there are WC and Co re fl ections, and in addition, the presence of the W 2 C phase in the initial powder resulted in the formation of Co 3 W 3 C carbide, whose relative content does not exceed 16 ± 5 %. Fig. 6 shows the dependence of the lattice parameter and the degree of the WC phase tetragonality on the time of the powder mechanical activation; they change insigni fi cantly and are in good agreement with the literature data (ICDDPDF2 65-4539) [25]. Figure 7 shows SEM images of the structure of sintered samples and the grain size distribution. Pores are visible in the structures, the WC-phase grains have an irregular geometric shape (light areas), the W 2 C phase (gray areas) is distributed mainly around the WC-phase grains. WC grains and the W 2 C phase are uniformly distributed throughout the sintered sample. The average WC-phase grain size decreases with increasing machining time from 1.1 μ m ( σ = 0.6 μ m) to 0.8 μ m ( σ = 0.3 μ m) (at 300 s of powder machining). Figure 8 shows the porosity of sintered samples depending on the time of the powders mechanical activation. It shows that at 10 s of processing the porosity is 11.6 ± 0.2 %, at 30 s of activation the porosity has a minimum value of 7.8 ± 1 % due to the destruction of agglomerates, and then begins to increase to 13.6 ± 1.5 % at longer processing. Fig. 5. XRD patterns of sintered samples depending on the milling time of powder