Page 11 - НАЦІОНАЛЬНА АКАДЕМІЯ НАУК УКРАЇНИ
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particle size of SiC, the temperature of heating of the samples immediately before
surface modification by laser. It was revealed that with increasing linear energy of the
laser beam, the thickness of the modified layer increases and the volume content of
SiC particles in it increases. With an increase in linear energy of more than
1100 J/cm, SiC particles intensively dissolve in the aluminum melt, which affects the
characteristics of the layer. Therefore, it was accepted that the linear heat is optimal
in the range of 740 ... 1100 J/cm. At a linear energy of 740 J/cm, the uniform
distribution of SiC particles over the thickness of the modified layer is retained only
to a depth of less than 0.9 mm, while at 1100 J/cm - up to 1.1 mm.
At a linear energy of 1100 J / cm, with an increase in the particle size of SiC
from 50 to 150 μm, the thickness of the modified layer increases from 0.75 to
1.5 mm, and their volumetric content in it increases from 16 to 20.5%.
X-ray spectral and X-ray phase analysis of the layers modified with SiC
particles confirmed the presence of silicon carbide particles and aluminum carbides in
them. The mechanism of the formation of laser-modified (by SiC particles) surface
layers on aluminum alloys is disclosed. It has been established that in the upper zone
of the modified layer, where the melt temperature is the highest, globular Al4SiC4
particles and needle-shaped Al 4C 3 particles in the lower zone are formed due to
aluminum diffusion into the SiC surface layer. When the aluminum content in the
surface layer of SiC particles reaches 8 ... 10 wt.%, due to stress, the resulting
particles of aluminum carbides are separated from the surface of SiC particles and
distributed by the convective flows throughout the volume of the modified layer.
It was established that during friction, the wear resistance of laser-modified
layers depends on the following factors: the chemical composition of the aluminum
alloy, the volume content of SiC particles in the modified layer, the linear energy of
the laser beam, the overlap width of the laser tracks, and the direction of abrasive
wear.
Assessing the effect of the chemical composition of aluminum alloys (АМг1,
АD35, В95) on the wear resistance of laser-modified (by SiC particles) layers, it was
found that with an increase the zinc content in the alloy, the wear resistance of these