Page 11 - Stanochny park

METALWORKING EQUIPMENT AND TOOLS

Technique, materials and equipment
The deposition of a copper coating on a ShKh15 steel
substrate was carried out on a DIMET-404 gas-dynamic setup
using a mechanical mixture of corundum (Al2O3) and copper
particles as supplied [4]. A copper coating was applied
to the surface of samples measuring 4 x 20 x 23.8
mm at a temperature of 450 °C and 270 °C with a
thickness of up to 1 mm. The surface of the coated
samples with an area of 95.2 mm2 was processed
on a grinding machine to a metal layer thickness of
≈450 μm and burned in with sandpaper.
Wear testing of coated specimens was
carried out in tandem with a counterbody made of
ShKh15 steel with dimensions of 8 x 25 x 80 mm
on a stand for reciprocating motion of conjugated
MT-8 specimens [5]. The reversible type of
movement of samples of a friction pair is one of the
most difficult, it allows more contrast to reveal the
advantages or disadvantages of one or another type of
processing of structural materials.
Technical characteristics of the friction machine: average sliding speed in a friction pair -
0.1 - 0.4 m / s; moving sample stroke - 1 - 40 mm; the greatest load on a pair - 1250 N; engine
speed - 930 rpm; power consumption - 1.1 kW; the greatest friction force - 25 kgf; overall
dimensions of the machine, mm: length - 1150, width - 940, height - 990; machine weight -
200 kg.
Two samples were used for testing, one of which was a sample with a smaller friction
surface – coated steel. This sample was stationary and a load was applied to it. The second sample
(counterbody) was located at the bottom, made of ShKh15 steel and performed reciprocating
movements relative to the stationary sample with an average sliding speed of 0.19 m / s and its
movement was 0.04 m. The tests were carried out with a stepwise increase in the load of 1.0;
2.0; 2.5; 3.0; 3.5; 4.0; 4.5; 5.0; 5.5; 6.0 6.5; 7.0; 8.0; 9.0; 10.0 with running-in in the range
of 0.2 - 1.0 kgf. The test time is 1 hour at each load level.
The surface profile of the counterbody and copper coating before and after tests was
investigated using a TIME TR 200 profilograph-profilometer according to the international standard
ISO 4287 with an assessment of the microroughness value by Ra, Rz, Rt. On the
surface of the counterbody, the surface microgeometry was investigated in two
directions, namely, parallel (PR) and perpendicular (PD) to the sample movement.
The hardness of the counterbody was measured on a microhardness meter
HMV-2 (SHIMADZU) at a load of 0.1 kg according to the Vickers method
[GOST 2999-75] with automatic recalculation of the Rockwell value (HRC).
The hardness of the copper coating for each spraying mode was determined
on three reference specimens at a load of 0.025 kg.
The hardness of the copper coating applied at a low airflow temperature
is 138.5 HV 0.025 / 10, which is ≈25 units more than that of the copper
coating sprayed at 450 °C, which is 113.6 HV 0.025 / 10. The difference
in the hardness of the coating is due to the processes of return (rest)
taking place in the deformed metal when it is heated [5].
The hardness of counterbodies made of ShKh15 steel and subjected
to heat treatment is in the range of 56.0 - 58.5 HRC.
Analysis of the results of measuring the parameters of the surface
profile of samples with copper coating shows that, in accordance with GOST
2789 - 59, a copper coating applied at an airflow temperature of 450 °C,
after mechanical treatment has 9 - 11 purity classes. A similar mechanical
treatment of a copper coating sprayed at a lower temperature of the air
flow (270 °C) is accompanied by the formation of a higher quality surface
- grade 11 cleanliness, which may be associated with a higher hardness of
the coating metal.

Stanochniy park 11