|
5283 |
|
Influence of the size and velocity of the particles on the structure and properties of electric-arc sprayed coatings |
|
Rico Drehmann / Chemnitz University of Technology, Germany Mykhailo Student / National Polytechnic University Lviv, Ukraine Volodymyr Hvozdetskyi/ National Polytechnic University Lviv, Ukraine Taras Stupnytskyi/ Karpenko Physico-Mechanical Institute of NASU, Ukraine Volodymyr Posuvailo/ Karpenko Physico-Mechanical Institute of NASU, Ukraine Hanna Pokhmurska*/ Chemnitz University of Technolgy, Germany |
|
The increase of the air flow pressure by arc spraying from 0.6 to 1.2 MPa results in an increase of the velocity of the atomized particles from 300 to 600 m/s. The increase of air flow speed reduces the flight time of the droplets from the arc to the substrate resulting in an increased impact temperature of the particles. The increase of the air pressure reduces the size of the particles and the thickness of the oxide films between lamellae as well, thus improving the mechanical characteristics of the coating. Increasing the pressure of the air flow from 0.6 to 1.2 MPa promotes an intense dispersion of the melt of the electrode wire leading to a reduction in the size of the droplets which form the coating. The reduction of the droplet size provides an increased area of contact with air and consequently their partial or total oxidation, which increases the amount of oxides and promotes the formation of the composite coating structure. The CWCr6B3Al6Mg2 coatings sprayed at a pressure of 0.6 MPa and 1.2 MPa demonstrate an increase of micro hardness from 600...650 to 850...900 HV, respectively. This is ensured by a higher content of aluminum oxide (micro hardness of Al2O3 is 2000 HV) and a more uniform distribution of FeCrB2 in the coating structure. |