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Microplasma-sprayed multilayer coatings for electric heating elements

Sergii Kaliuzhnyi
Sergii Kaliuzhnyi
, 
Darya Alontseva
Darya Alontseva
, 
Sergey Voinarovych
Sergey Voinarovych
, 
Oleksandr Kyslytsia
Oleksandr Kyslytsia
, 
Aleksandr Khozhanov
Aleksandr Khozhanov
, 
Leszek Łatka
Leszek Łatka
, 
Zulfat Faizrakhmanov
Zulfat Faizrakhmanov
 and 
Gulsym Bektasova
Gulsym Bektasova
   | May 02, 2023
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Published Online: May 02, 2023
Page range: 158 - 170
Received: Nov 23, 2022
Accepted: Jan 30, 2023
DOI: https://doi.org/10.2478/msp-2022-0049
Keywords
© 2022 Sergii Kaliuzhnyi et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Fig. 1

Scheme of EHE tests: U – regulated power supply; K – switch for interrupting the supply of electric current; A – ammeter; V – voltmeter; R – a sample with an electric heating coating; T – thermal imager. EHE, electric heating element
Scheme of EHE tests: U – regulated power supply; K – switch for interrupting the supply of electric current; A – ammeter; V – voltmeter; R – a sample with an electric heating coating; T – thermal imager. EHE, electric heating element

Fig. 2

Scheme for measuring the metallization figure, where H is the spraying distance, β is the opening angle of the plasma jet, h is the height of the sprayed material, L is the vertical (large) axis, and l is the horizontal (small) axis of the spray spot
Scheme for measuring the metallization figure, where H is the spraying distance, β is the opening angle of the plasma jet, h is the height of the sprayed material, L is the vertical (large) axis, and l is the horizontal (small) axis of the spray spot

Fig. 3

Diagram explaining the loss of material due to the geometric factor
Diagram explaining the loss of material due to the geometric factor

Fig. 4

EHE appearance: (A) EHE Series No 1: two-layer coating of Al2O3 and TiO2; (B) EHE Series No. 2: three-layer coating of Al2O3 and TiO2. EHE, electric heating element
EHE appearance: (A) EHE Series No 1: two-layer coating of Al2O3 and TiO2; (B) EHE Series No. 2: three-layer coating of Al2O3 and TiO2. EHE, electric heating element

Fig. 5

Microstructure of the three-layer coating of EHE Series No. 2: 1 – steel substrate; 2 – Al2O3 layers; 3 – TiO2 layer. EHE, electric heating element
Microstructure of the three-layer coating of EHE Series No. 2: 1 – steel substrate; 2 – Al2O3 layers; 3 – TiO2 layer. EHE, electric heating element

Fig. 6

Temperature distribution along the electric heating track depending on the heating time; at the beginning of the process (A); every next 35 s (B, C); after 100 s (D)
Temperature distribution along the electric heating track depending on the heating time; at the beginning of the process (A); every next 35 s (B, C); after 100 s (D)

Fig. 7

Cross section of metallization figures along the spray spot axes (Run 6, Table 5): (A) section along the large axis y = 2.27 × e−0.36x2; (B) section along the small axis y = 2.27 × e−0.78x2; graph of the Gaussian distribution (calculated); the actual profile of the metallization figure
Cross section of metallization figures along the spray spot axes (Run 6, Table 5): (A) section along the large axis y = 2.27 × e−0.36x2; (B) section along the small axis y = 2.27 × e−0.78x2; graph of the Gaussian distribution (calculated); the actual profile of the metallization figure

Fig. 8

Losses of the sprayed material associated with the geometric factor depending on the width of the electric heating track: (A) for the large axis L of the spray spot; (B) for the small axis l of the spray spot
Losses of the sprayed material associated with the geometric factor depending on the width of the electric heating track: (A) for the large axis L of the spray spot; (B) for the small axis l of the spray spot

Parameters of MPS of electrically insulating and resistive coatings

Parameters Coating
Al2O3 TiO2
Electric current, I (A) 45 40
Voltage, U (V) 30 28
Spraying distance, H (mm) 150 150
Plasma-forming gas (Ar) flow rate, Gpl (slpm) 1.3 1.3
Shielding gas (Ar) flow rate, Gsh (slpm) 4.0 4.0
Powder feed rate, Ppow (g·min−1) 1.2 2.0

Chemical composition of carbon steel St3 according to Ukrainian State Standard DSTU 2651:2005, 2015

Elements Wt.% of elements
C 0.14–0.22
Si 0.15–0.30
Mn 0.40–0.65
Ni <0.3
Cu <0.3
Cr <0.3
As <0.08
N <0.008
S <0.05
P <0.04
Fe Balance amount

The CTE values depending on the parameters of the MPS of TiO2 powder

Run I (A) Gpl (slpm) H (mm) Ppow (g·min−1) CTE, %
Experimental Calculated
1 45 2.0 160 1.8 75 74
2 45 2.0 80 0.6 89 96
3 45 1.0 160 0.6 44 44
4 45 1.0 80 1.8 78 84
5 35 2.0 160 0.6 47 50
6 35 2.0 80 1.8 88 91
7 35 1.0 160 1.8 28 38
8 35 1.0 80 0.6 65 61
9 40 1.5 120 0.8 68 64

Parameters of the metallization figure depending on the parameters of the MPS of TiO2 powder

Run I (A) Gpl (slpm) H (mm) Ppow (g·min−1) Metallization figure height, h (mm) Large axis, L (mm) Small axis, l (mm)
1 45 2.0 200 1.8 2.21 9.2 7.5
2 45 2.0 100 0.6 1.04 6.3 4.7
3 45 1.0 200 0.6 0.53 8.2 7.4
4 45 1.0 100 1.8 2.31 7.2 5.6
5 35 2.0 200 0.6 0.35 8.8 6.2
6 35 2.0 100 1.8 2.27 8.6 6.6
7 35 1.0 200 1.8 0.81 7.2 7.0
8 35 1.0 100 0.6 1.34 7.6 5.4

Intervals of variation of the parameters of MPS of electric heating tracks (TiO2)

Levels of variation Factors
Electric current, I (A) Plasma-forming gas flow rate, Gpl (slpm) Spraying distance, H (mm) Powder feed rate, Ppow (g·min−1)
Upper level + 45 2.0 160 1.8
Lower level − 35 1.0 80 0.6
Base level 0 40 1.5 120 1.2
Variation intervals 5 0.5 40.0 0.6
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