he bend into the shape of “U” in the test preparation occurred in the interval of radii of curvature from R11 to R35 mm STEEL breach of the coating (Figure 6).
In the second stage of the experiment was used in conjunction with MU Brno multi-jet plasma system (Figure 7).
Figure 4. The thickness of Al coating on steel sheet, sample 15, side A.
Figure 5. Thickness of coating STEEL, sample 15, side A.
Figure 6. Photo of damaged coating STEEL after the bending without application of plasma.
Figure 7. Sample of multi-jet system used in the experiment .
with a width of 100 mm with nineteen jets providing low-temperature and non-isometric discharge at atmospheric pressure.
The physical nature of the phenomenon of plasma multi-jet system consists of generating plasmas at atmospheric pressure.
3. The Principle of High-Frequency Hollow Cathode (13.56 MHz)
The basis of nozzles was used dielectric capillaries made of silica glass, which flows through the argon, including any additions.
The resulting plasma jets from the mouth cavity of the plasmic-jet into the external environment, which acts on the coated steel samples.
Discharge for the entire length of plasma channel active generated.
Absorbed power of the plasma channel was used multi-jet device according to selected working conditions in the range from 102 to 103 W·cm–2.
Unlike welding, electron beams, where the power density at the point of welding to 109 W·cm–2 .
Thermal effects on the surface of samples can be in range from 30˚C to 1600˚C while maintaining non-isometric character of discharge (temperature of energy particles of 10,000 K).
On the based these properties of plasma-jet system can provide a highly reactive compound with high efficiency for the chemical and physical modification of the surface material.
A suitable grouping of nozzles (jets) in linear or other formations allows cutting of large areas of test samples respectively semi-finished steel in industrial practice [18, 19].
The result of the application used multi-jet system on the test specimens with Al coated on the set of optimal parameters of plasma jets flowing out of nineteen, (knowhow process), was subsequently applied coating STEEL, which had no signs of damage after bending the sample on the graduated bending jig (Figure 8).
On the based of bending experiments of steel samples with a nominal thickness of 1.5 mm, width 18 mm and lengths in interval from 98 to 181 mm of low-carbon steel according to DIN EN 327 with sprayed coatings Al thickness of 25 ± 5 μm and STEEL 47 ± 7 μm were found:
Performing of the bending on the cylindrical thorns with radii R11, R17, R23, R29 and R33 without application of plasma with a functional surface of tested coatings is impossible without their defects.
After application and optimalization of plasma parameters using the plasma system was made functional coatings for cylinder radii R29 and R33 in the test graduated bending JIG.
For smaller radii of test cylinders, i.e. there were slight defects in the coating STEEL.
Graduated bending test JIG used for experiments was newly developed and introduced for testing by bending sheet metal into the shape of “U” at the Institute of
Figure 8. Photo of functional coating STEEL after the bending with the application of plasma made in graduated bending jig with rollers at BUT BRNO.
Engineering Technology in BUT (BRNO UNIVERSITY OF TECHNOLOGY).
*The article is supported by the grant project, VUT FSI Brno—BD 1393016 from 2009.