Механика машин, механизмов и материалов (Dec 2018)
Effect of Air Atomization Pressure at High-Speed Spraying of Gas-Thermal Coating from High-Chromium Steel on its Construction and Wear Resistance
Abstract
The influence of the pressure of the atomizing air at high-speed spraying of the gas-thermal coating from high-chromium steel 20Kh13 on the structure and wear resistance of the coating is studied. It is shown that sprayed gas-thermal coatings from 20Kh13 steel in the phase composition contain α-Fe and Fe3O4 and FeO oxides. It is established that with an increase in the pressure of air supply used to burn the MPS gas from 0.1 to 0.3 MPa, with gas-thermal spraying, the amount of oxides increases from ≈8 to ≈15 vol.%, and the porosity of coatings decreases from 5.0 to 2.5 vol.%. The hardness of sprayed coatings from 20Kh13 steel increases with air pressure from 220 to 320 HV 10. The increase in hardness of coatings with increasing air pressure is associated with an increase in the volume fraction of Fe3O4 and FeO oxides contained in the coatings. The intensity of mass wear under conditions of dry friction of a gas-thermal coating of 20Kh13 steel sprayed with a minimum air pressure of 0.1 MPa, under conditions of dry friction is 20.2 ∙ 10–3 mg/m. The increase in air pressure up to 0.3 MPa leads to the decrease in wear resistance of coatings by 1.4 times, which is associated with the increase in the number of brittle oxides in coatings. The intensity of linear wear in the I-20 lubricant of coatings obtained at a minimum pressure of spraying air of 0.1 MPa is 0.255 ∙ 10–9. With the increase in air pressure during spraying up to 0.3 MPa, the wear resistance of coatings under conditions of boundary friction increases by ≈1.3 times, which is caused by the increase in the durometric properties of coatings.
