PSI - Issue 20

Yakovleva S.P. et al. / Procedia Structural Integrity 20 (2019) 190–197 Yakovleva S.P. et al. / Structural Integrity Procedia 00 (2019) 000–000

192

3

rigidity of diamond grains fixing in a binder, a mixture of powders of iron-carbon alloys with different hardness levels was used in its composition (table 1).In mixtures the percentage of components was changed: the content of soft powder P1 in them was 20, 30 and 40 %, the rest is P2 solid powder, commonly used for spraying. Diamond powder brand А 7 К 80 500/400 was introduced into the matrix powders at a rate of obtaining 100% of their content in a non-porous compact. This powder is a collection of diamond grains of different shapes (Fig. 1); well-developed cutting edges of grains favor abrasive properties of composites.

Table 1. The chemical composition of the binder powders (%) and their microhardness. Powder C Si Ni Mn Cr Mo

В

Fe

H, MPa

P1 P2

0.05-0.12

≤ 0.2

7-10

-

16-20 32-37

≤ 0.5

-

res.

1800 6900

3.5-5.5

1.0-2.5

-

1.5-4.0

-

1.3-2.0 res.

The explosive pressing was carried out according to a cylindrical loading scheme, which makes it possible to obtain compacts that are sufficiently homogeneous in their properties by Buzjurkin et al. (2010), Buzjurkin et al. (2002). Regimes differing in impact power were used, for which the diameter D of the explosive backfill ( D 1 = 45 and D 2 = 50 mm) was varied. The compacted samples were subjected to short-term high-temperature heating in three modes at temperatures of 600, 800 and 900 o C. Analytical complex studies were conducted by standard methods. The metallographic analysis was performed on Neophot-32 and Axio Observer D1m microscopes. The microhardness of the phases was measured using a PMT-3 instrument at a load of 2 N. The structure and fracture surfaces were investigated on a Stemi 2000 С stereoscopic microscope and on a JSM-6480 LV JEOL scanning electron microscope. Granulometric analysis and study of the static strength of diamond grains in the initial state and after recovery were carried out due to the standard methods in accordance with GOST 9206-80.

a

b

c

d

Fig. 1. Diamond powder А 7 К 80 500/400 brand (a), macrosurface of DMC fracture (b) and areas with diamond particles on the non-etched DMCmicrosections up to (c) and after heat treatment at 900° C (d). The composition of the DMC matrix: 40% P1 powder and 60% P2 powder. Explosive pressing at D 2 = 50 mm. Arrows indicate diamond grains in DMC.