Correlation Between WC-Ni Particle Velocity/Temperature And Coating Characteristics By HVOF

WC-Ni cemented carbide coating prepared by High Velocity Oxy-Fuel?HVOF?technology has excellent properties such as high hardness,high strength and high wear resistance.In the process of High Velocity Oxy-Fuel,the speed and temperature of spraying particles are the decisive factors that directly affect the characteristics of coatings.However,the speed and temperature of spraying particles depend on the selection of spraying parameters such as kerosene flow rate,fuel ratio,spraying distance.In this paper,first.I measured particle velocity and temperature under different spraying gun parameters and different spraying distances using particle velocity and temperature detection system.Then,I established the quantitative relationship between particle velocity,temperature and coating characteristics,selecting WC-12Ni Cemented Carbide Coatings prepared by spraying parameters corresponding to different particle velocity and temperature,investigating the influence of particle velocity and temperature on the porosity and phase composition of coatings,analysing the mechanical properties of coatings and expressed the quality of coatings by the impact resistance of coatings.I do all these to improve the spraying process and obtain higher quality WC-Ni cemented carbide coating.Research results show that:?1?At the same spraying distance,with the increase of the value of?,the velocity of spraying particles increases but the temperature of spraying particles decreases.When kerosene flow rate is 22.7 L/h,?increases from 1.05 to 1.43,the flying speed of particles increases from810 m/s to 865 m/s,but the temperature of particles decreases from 1981?to 1915?.If at the same?,the velocity and temperature of particles decrease with the increase of spraying distance.When the kerosene flow rate is 19.3 L/h and?is 1.05,the spraying distance increases from 200 mm to 400 mm,but the particle velocity decreases from 941 m/s to 848 m/s,and the temperature of particles decreased from 1948?to 1824?.?2?The decomposition amount of WC in the obtained coating decreases with the decrease of particle temperature.The average retention rate of WC was 71.02%at 1948-1974?and79.46%at 1795-1845?.With the increase of particle velocity,the porosity of the coatings decreases.The microhardness of WC-12Ni coatings increases from 11.10 GPa to 13.35 GPa when the particle temperature was from 1948 to 1974?,the particle velocity increases from820 m/s to 950 m/s,the porosity of WC-12Ni coatings decreases from 1.4889%to 0.8563%.?3?The impact resistance of coatings is determined by the interaction of mechanical properties and microstructures of coatings.The higher hardness of the coating is,the higher retention of WC is,and the stronger impact resistance of the coating is.When the particle temperature is between 1948?to 1974?,the particle velocity increases from 820 m/s to 950m/s,and the impact crater area decreases from 1.8310×10^-4 mm² to 0.3415×10^-4 mm².And the particle velocity increases from 820 m/s to 890 m/s and the impact crater area decreases from0.9489×10^-4 mm² to 0.4766×10^-4 mm² when the particle temperature is between 1795?and1845?.When the particle velocity is increased to 950 m/s,there is no dent on the surface of the coating after impact.The impact resistance of coatings obtained at particle temperature from1795?to 1845?is higher than that of coatings obtained at particle temperature from 1948 to1974.