Tomasz Babul

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Tomasz Babul
TEMPERATURE OF NiCrBSi POWDER PARTICLES
DETONATION SPRAYED THEORY AND PRACTICE
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DETONATION THERMAL SPRAY

• Advantages of the detonation thermal spraying
• Low substrate temperature the heat transferred
  to the substrate stays very low. The substrate
  temperature, during spraying, does not exceed
  150oC.
• The highest velocity up to 1300 m/s.
• Low 0.3 porosity and high 250 MPa adhesion.
• Low cost of operation
• consumption of oxygen is only 310 of HOVF (20
  to 30 l/m),
• less electrical energy consumption very
  effective electric power consumption - the unit
  consumes a total of 200 W,
• less downtime  the process is very simple to
  operate and very reliable. There are literally no
  components that can wear out, similar to Laval
  nozzle in the HVOF gun.
• Can be sprayed multi-type powder from low melting
  point metal to high melting point of ceramics.

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THERMAL SPRAYING
(www.gtv-mbh.com)
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DETONATION SPRAYING DEVICE
Device for detonation spraying
(www.aflame.com)
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RESEARCH METHODOLOGY

• The used powder
• alloy NiCrBSi
• granulation of 2545 µm
• chemical composition
• Ni 70
• Cr 16
• Si 4
• B 4
• Fe 4
• C 2
• powder hardness 700HV

The morphology of the NiCrBSi
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DETONATION SPRAYING DEVICE

• To determine the stream velocity as a function of
  the stream acceleration way, there was used
  device with replaceable barrels.
• Barrels with length of 110 mm, 140 mm, 210 mm,
  310 mm, 410 mm, 510 mm and 610 mm were used.

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TEMPERATURE MEASURING SYSTEM
Recording and archiving of output signals were
performed using a four-channel digital
oscilloscope Tektronix TDS type 460.
System for measuring the stream temperature
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TEMPERATURE OF THE NiCrBSi POWDER
Temperature (series of 5 meas.)
Temperature of the NiCrBSi powder stream as a
function of time measured for the barrel length
110 mm
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TEMPERATURE OF THE NiCrBSi POWDER
Temperature (series of 5 meas.)
Temperature of the NiCrBSi powder stream as a
function of time measured for the barrel length
260 mm
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TEMPERATURE OF THE NiCrBSi POWDER
Temperature (series of 4 meas.)
Temperature of the NiCrBSi powder stream as a
function of time measured for the barrel length
510 mm
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TEMPERATURE OF THE NiCrBSi POWDER
Temperature (series of 4 meas.)
Temperature of the NiCrBSi powder stream as a
function of time measured for the barrel length
610 mm
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TEMPERATURE MEASUREMENTS SUMMARY
Temperature changes for a NiCrBSi powder stream
as a function of the barrel length
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FEM MODEL
The values of physical constants for Ni powder
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MODEL ASSUMPTIONS

• Temperature distributions were calculated by
  finite element method FEM, using the COSMOS/M
  program algorithm. It was assumed that the heat
  exchange takes place in the material according to
  the conduction mechanism described by Fouriers
  Law relationship
• where
• T - temperature,
• t - time,
• cp - specific heat,
• r - density,
• q - heat stream,
• ki - thermal conductivity with i-direction.
• The heat transfer between the considered system
  and the environment takes place in accordance
  with the convection mechanism where heat stream
  is expressed by the following equation
• where
• hc - heat transfer coefficient,
• T - considered surface temperature,
• T8 - ambient temperature.

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MODEL SENSITIVITY ANALYSIS ON THE TEMPERATURE
DISTRIBUTION IN SPHERE f25 um

• The purpose of this analysis is to examine the
  impact of model parameters on calculated
  temperature value at the considered system point.
• As a sensitivity measure was adopted
  dimensionless index calculated from the following
  equation
• where
• T - temperature of the considered point,
• pi - i-time model parameter.
• This indicator determines the sensitivity of
  calculated temperature value at the considered
  system point for the model parameter change. The
  value of this indicator equal to unity means,
  that changing the considered parameter for 100,
  the calculated temperature value will change also
  by 100. Sensitivity indicator value equal to
  W-0.5 means, that increasing the considered
  parameter for 100, the calculated temperature
  value will be reduced by 50, etc. The results of
  such indicator calculations can be used to
  evaluate model parameters that have the most
  significant impact on the temperature
  distribution of the analyzed object.

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MODEL PARAMETERS

• As the parameters of the model were adopted
• p1 sphere diameter,
• p2 heat transfer coefficient,
• p3 specific heat,
• p4 density,
• p5 thermal conductivity,
• p6 outside temperature (ambient temperature),
• p7 initial temperature.
• By comparing the absolute values of the
  sensitivity indicator calculated for the
  temperature at time t4 ms, the model parameters
  can be arranged by decreasing impact as follows

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MODEL PARAMETERS

• On the sphere surface
• p6 outside temperature (ambient temperature),
• p2 heat transfer coefficient,
• p3 specific heat,
• p4 density,
• p1 sphere diameter,
• p5 thermal conductivity,
• p7 initial temperature.

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MODEL PARAMETERS

• Inside the sphere
• p6 outside temperature (ambient temperature),
• p1 sphere diameter,
• p3 specific heat,
• p4 density,
• p2 heat transfer coefficient,
• p5 thermal conductivity,
• p7 initial temperature.

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EFFECT OF HEAT TRANSFER COEFFICIENT
Effect of heat transfer coefficient on the value
of temperature calculation on the surface of a
sphere (Ni) with a diameter of 45 µm
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EFFECT OF HEATING TIME
Effect of heating time on the value of the
calculated temperature on the surface of nickel
powder with a diameter of 25 and 45  µm
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THE TEMPERATURE DISTRIBUTION
The temperature distribution along the radius of
nickel powder with a diameter of 25 µm after 10,
50, 100, 200, 300 and 400 µs
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THE TEMPERATURE DISTRIBUTION
The temperature distribution along the radius of
nickel powder with a diameter of 25 µm after 10,
50, 100, 200, 300 and 400 µs
The temperature distribution along the radius of
nickel powder with a diameter of 45 µm after 10,
50, 100, 200, 300 and 400 µs
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PRACTICE AND THEORY COMPARISON
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PRACTICE AND THEORY COMPARISON
Heat Transfer Coefficient 100 W/(m2K)
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PRACTICE AND THEORY COMPARISON
Heat Transfer Coefficient 100 W/(m2K)
Heat Transfer Coefficient 10 W/(m2K)
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CONCLUSIONS

• The calculations for the assumed boundary
  conditions have shown that the particles surface
  heating depends primarily on the ambient
  temperature (temperature of the gaseous
  detonation products) and depends on adopted for
  the calculations value of heat transfer
  coefficient.
• Changing the value of heat transfer from 10
  W/(m2K) to 100 W/(m2K) causes that the calculated
  theoretical time needed to heat the powder
  surface extends approximately 6-times, i.e. from
  about 0.5 ms to over 3.0 ms.
• It has been shown that in the case of adoption of
  a constant heat transfer coefficient value for
  the calculations, the powder granulation (in the
  range of 25 µm and 45 µm) did not significantly
  affect on the duration of its surface heating to
  the detonation products stream temperature.
• Maximum duration of surface heating to the
  ambient temperature (temperature of the gaseous
  detonation products T83273 K) is equal about 0.5
  ms. It is worth to mention that calculations
  shows that the powder temperature is almost
  identical on its surface and inside which
  indicates the intensive heat transfer from the
  surface into the material which is characterized
  by thermal conductivity. Due to the size of the
  individual powder particles, calculated results
  seem to be likely especially for smaller
  diameters.
• A comparison of the graphs obtained for the
  experimental measurements and calculations using
  the FEM method shows their high compatibility.

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Thank you for attention!
e-mail tomasz.babul_at_imp.edu.pl