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
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