Page 13 - НАЦІОНАЛЬНА АКАДЕМІЯ НАУК УКРАЇНИ
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fixed abrasive, the erasure of all phases of the modified layer occurs layer-by-layer
almost uniformly over the entire friction surface. In this case, there were no deep
traces of abrasion and avulsion caused by the grasp of the abrasive wheel with the
sample surface. This is due to the increased hardness of the matrix around the SiC
grains, which is micro-reinforced with dispersed carbides Al 4C 3, Al 4SiC 4, and
therefore less prone to plastic flow as prerequisites for avulsion.
The low wear resistance of the alloy laser-modified by SiC particles during
friction with a non-fixed abrasive is since free abrasive falling into the gaps between
solid SiC particles easily destroys the soft matrix, releasing them. After this, the
particles are pulled out without a special effort by a rubber circle. The wear resistance
under friction with a non-fixed abrasive depends on the distance between the SiC
particles because the modified surface of the aluminum alloy is destroyed primarily
around these particles.
Since the work purpose was to replace galvanic chrome plating, it was found
that laser modification under friction with a rigidly fixed abrasive increases the wear
resistance of the output alloy by 40-95 times, and galvanic chrome plating only by
35 times, however, in case of friction with non-fixed abrasive, laser modification was
not very effective. Therefore, was justified the choice of another method of surface
hardening. This method turned out to be the method of thermal spraying, as one of
the most productive and simple to implement.
Therefore, the structure and wear resistance of the thermal coatings of the
FeCr-VC system obtained by high-speed flame spraying (HVOF) and plasma
spraying in dynamic vacuum (PSCDV) were studied.
The structures of the VC-FeCr systems coatings, obtained by high-speed flame
spraying (HVOF) on equipment in which propane oxygen (Diamond Jet Hybrid gun)
and kerosene - oxygen (JP5000 gun) served as fuel, were almost identical. They are
characterized by a typical lamellar structure, when slightly deformed drops of powder
mixtures used to obtain coatings are crystallized, lamellas with barely noticeable
oxide layers between them form. Against the background of the matrix phase of
ferrochrome, stochastically dispersed precipitates of VC carbides with a size of