Effect of plasma surfacing parameters on vanadium carbide microstructure in powder coatings based on PR-Cr18VNiMo

Abstract

The vital importance of the investigation is caused by forming the volume homogeneous structure and the phase composition of composite coatings to give them wide range of operational requirements. The paper seeks to study in detail the change of average volume fraction, size, carbide-vanadium particles shape factor, uniformity of their distribution depending on current intensity and the feed speed of PR-Cr18VNiMo powder in a plasma-powder deposition with the direct current. The microstructure analysis of the coatings was carried out with Olympus GX51 optical microscope supplied with SIAMS-700 image analyzer. The authors have carried out the phase composition investigations of the depositions using X-ray diffraction analysis by means of Shimadzu XRD-6000 diffractometer with CuK filtered α-radiation. The studies revealed the influence of plasma surfacing parameters such as current straight polarity and powder feed rate of PR-Cr18VNiMo on vanadium carbide microstructure. With the increasing powder feed rate in the range of current of 220...260 A the VC particle shape factor grows linearly. At rate exceeding 1,5 kg/h the VC particle shape factor become equiaxed. The use of surfacing coating currents of 160...200 A promotes the release of equiaxed particles. In this case their form factor does not depend on the powder feed rate.

Keywords

• plasma-jet hard-facing
• composition coating
• austenitic steel
• vanadium carbide
• structure