ABOUT PLASMA 4 th State of Matter mixture of ions, electrons & - - PowerPoint PPT Presentation
ABOUT PLASMA 4 th State of Matter mixture of ions, electrons & neutrals Highly reactive Accelerates chemical reactions Reduces processing times Homogenous processing (cold plasma) Environment Friendly Broadly classified as Thermal
Thermal Plasma Te Tg (Hot Plasma) Glow Discharge Plasma Te >>> Tg (Cold Plasma)
Broadly classified as 4th State of Matter – mixture of ions, electrons & neutrals Highly reactive Accelerates chemical reactions Reduces processing times Homogenous processing (cold plasma) Environment Friendly
Plasma based coatings Plasma Assisted Vapour Deposition Plasma sprayed coatings Plasma CVD Plasma PVD
Untreated surface Deposition Diffusion
Anti reflection coatings on solar cells
Increases efficiency of solar cells
Protective coatings on headlight reflectors
Prevents oxidation of Al coating on headlight reflectors and passivates the surface, thus increasing service life of reflectors.
Anti Tarnish coatings on brass / silver decorative articles
Passive transparent (SiOx) layer on silver / brass prevents it from being exposed to environment.
Diffusion barrier coatings on polymer films – Packaging
application
Prevents diffusion of oxygen into packed food. Imagine a pouch of milk not spoiling for over 6 months!!
Magnetron deposition With heating Magnetron deposition Without heating
N2 & H2 are fragmented to ions and radicals
by the glow discharge plasma surrounding the sample uniformly.
The ions and radicals diffuse inside the
sample because of high sample temperature.
The sample temperature is maintained by ion
and neutral bombardment and by external heating.
Process yields:
uniform case depth & hardness across the
surface
Low cycle times (faster processing) Eco-friendly processing elimination of post grinding operations
UHV PN System for Space Quality Plasma Nitriding Industrial Scale Plasma Nitriding Facility For Large size Industrial Jobs
Mould locking plates Crankshafts Connecting rods Cam chain sprocket
Parameter Value Barrel length, mm 1800 Barrel diameter, mm 22 Working gases: Fuel Oxidizer Powder carrier gas Acetylene Oxygen Nitrogen Firing frequency, Hz 2-4 Coating thickness per cycle μm 5-20 Typical coating thickness μm 50-500 Power consumption per hour, kW 2 Spraying distance 240mm
Working gases composition: mixture of a fuel gas, usually H2 or hydrocarbons, such as acetylene(C2H2), propane (C3H8)and butane (C4H10), with
Maximum temperature of 4200oC the Particle velocity of 3000 m/s Firing rate: is in the range 1‐15Hz.
Particle size: range 5‐60μm Powder feed rate: is in the range 16‐ 40g/min. Composition of carrier gas: Nitrogen or Air PRINCIPAL PROCESSING PARAMETER Spray distance: about 100mm. Spray atmosphere: is air COATING PROPETIES Bond strength: 83 and 70MPa. Porosities: 0.5% for WC‐Co coatings and about 2% for Al2O3 Thicknesses: Not exceeding 300μm.
Plasma spraying is used to apply surfacing materials that melt at very high
which acts as the second electrode. A pressurized inert gas is passed between the electrodes where it is heated to very high temperatures to form a plasma gas. Powdered feedstock material is then introduced into the heated gas where it melts and is propelled to the substrate at a high velocity. A plasma spray system consists of a power supply, gas source, gun, and powder feeding mechanism. Plasma spraying is primarily performed in fabrication shops. The process may be used to apply thermal barrier materials, such as zirconia and alumina, and wear resistant coatings such as chromium oxide.
Vacuum Plasma Technique
flow rate ranging from 90 to 200 slpm.
from 1500 to 3500 m/s.
that issuing from a plasma torch into an open atmosphere and can reach 250 mm.
greater than in APS and usually more than 80 kW.
‘de Laval’ type is often used
sprayed
Metals, Ceramics such as ZrO2+Y2O3 powders
PARAMETERS
which is added the working gas.
strength of SPS is in the range 20‐45 MPa.
range 1‐7%.
coatings are in the range 300 to 1500 µm.