Page 10 - дисертація Головчук
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tensile stresses are relaxed due to the formation of microcracks, which, however, do
not reduce their abrasive wear- resistance.
The feature of the change of gas-abrasive wear resistance of coatings from
these PW at the temperature of 200 °C is the same as abrasive one. Gas-abrasive
wear resistance of coatings (austenite of carbide class) from 250Cr21WVMnSi PW
decreased with increasing PW diameter and lamellar thickness, while in coatings
(martensitic class with boride inclusions) from 50CrNi25MnSi PW its value
increased and for coatings with larger diameter wear resistance was higher .
Based on the results obtained on model wires for further research powder
wires of martensitic class with borides inclusions were prepared with a diameter of
2.2 mm and different nature of chromium-containing components (chromium
content varied from 14.5 to 18.6 wt.%).
The coatings obtained from the developed PW had high hardness (from 560
to 700 HV 0,3), low level of the first-type residual tensile stresses, high cohesive
strength and low chemical microheterogeneity by the chromium content in lamellae.
It was revealed that by adding eutectic mixture of powders (FeSi + FeMn) or eutectic
powder PG10N-01 to the PW charge, it is possible to provide low chemical
microheterogeneity of coating (К mh = 0.05… 0.06) from PW with (Cr + B 4C),
(FeCrB 2 + Cr) and (FeCrB 2 + FeCr) refractory charge. FeSi powder does not provide
the formation of eutectic at the ends of the PW during its spraying. Therefore,
coatings with high microheterogeneity by chromium content in its lamellae and with
low corrosion resistance were obtained.
Tests for abrasion resistance of coatings from the developed PW showed that
coatings with lower second type-tensile stresses and higher modulus of elasticity are
characterized by higher wear resistance under conditions of fixed abrasive and by its
lower value under conditions with unfixed abrasive.
The maximum abrasion resistance of coatings under conditions of unfixed
abrasive is determined by the high microhardness of the lamellae in the coating made
of 75Cr19B3Si2 PW. In general, the developed coatings have 3-4 times higher wear
resistance compared to solid galvanically applied chromium coating. Such a high