IMPROVEMENT OF PLASMA COATINGS QUALITY CHARACTERISTICS

Developed by Ievgeniia Tarasova

Mechanical supervisor -Fedor

Vachkevich

English supervisor -Viktoria

Kuz’menko

The main idea of the present work is to develop plasma coating formulations and their application

technology that will allow to achieve maximal

performance characteristics.

Applications areas

Plasma spray coating is becoming more widely used in industry to protect a variety of parts and tools from wear, corrosion and erosion

Plasma coating is the one obtained by applying molten metal particles on a previously prepared

surface using a plasma jet.

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Improvement of plasma coating quality characteristics is held in the following

areas:

• activities to improve the quality by pretreatment of powders and protected surface;

• activities for coatings quality improvement during the process of spraying (technological regimes optimization);

• activities for coatings quality improvement by treating surfaces after their formation

Technological parameters that influence coatings formation and

micro-asperities hight are: • spraying distance

• spraying angle of a pneumatic gun

• abrasive particle size

• air pressure

• powder consumption

• speed of burner

Influence of dispersion distance (L) and slope angle of pneumogun (α) on the micro unevenness height(Rа)*

Rа·10-4м

L мм α=30о α=45о α=60о α=90о Note

50 54-56 57-59 63-66 71-74 *Got at permanent air pressure, diameter of nozzle of 5*10-3m and the abrasive size 0,5*10-3m

75 56-58 63-65 72-74 86-89

100 58-60 65-68 75-77 93-96

125 56-58 62-64 71-73 86-90

150 54-56 56-58 64-66 77-99

Table1

Influence of abrasive size (μ) and air pressure (Р) on the micro

unevenness height (Rа)

Rа·10-4м

μ*10-3м Р=0,2МПа Р=0,4МПа Р=0,6МПа Note

0,1 43-45 50-52 56-57 Information is got at the distance L=0,10m, nozzle diameter

of 5·10-3m, the slope angle α=90o

0,2 52-54 60-63 69-71

0,3 60-62 71-73 81-84

0,4 63-71 81-83 94-96

0,5 76-79 93-96 106-109

0,6 84-87 101-104 118-120

Table2

The table data (tabl.1 and tabl. 2) analysis showed that:

with reduction of slope angle of pneumogun to the surface of detail the surface roughness also reduses at permanent distance from pneumogun to the detail and identical compressed air pressure;

the increase of abrasive particles size results in the increase of roughness at permanent compressed air pressure;

reduction of compressed air pressure results in the reduction of roughness at the identical abrasive particles size.

Fig.1 Influence of technological parameters of the plasma setting work on eventual properties of coverages.

Х1 –current strength(А); Х2 – tension on an arc (В); Х3 – expense of plasma-forming gas of argon (l/mine); АВСDЕ is the compromise region of the criteria У1, У2, У3, У4; FGDE is optimal spraying region of thermal coverages.

Mathematical method of prediction experiment

а) b) c) Fig.2 Structure of sprayed coverage from the SNGN alloy after melting:

a – in a stove with a low oxidizing atmosphere; b – currents of high-frequency; c – micro-plasma burner. х 200

In order to improve the coatings quality it is recommended to apply plasma and micro-plasma melting

Conclusion

1. The analysis of surface preparation approach used before spraying gave an opportunity to choose pnuematical surface preparation by means of electrolytic as the most efficient one since it allows to adjust the surface roughness in a wider range.

2. Mathematical investigation made it possible to create the range of criteria compromising by means of graphical-analytical approach. Moreover it allowed to make optimal range of gas-termal spraying.

3. Among all the investigated methods of surface melting aimed on quality improvement it is advisable to implement plasma and microplasma melting as it makes possible to achieve tight and strong coupling of protection layers of steel and titan.

All the investigations held in the research work allowed to develop technical tutorials used for producing improved quality features plasma surfaces.

THANKS FOR ATTENTION