From the inauguration of the motor vehicle in the late 1800’s, considerable change has been undertaken in the design and development of the motor vehicles we have today. The requirement for greater efficiency, speed and comfort whilst still being environmentally friendly is a key part of travel and requires materials which are lighter and more performance related. The Metal/Thermal spray process is used today to solve a lot of issues. The above video shows the Metal Spraying of a Land Rover Chassis - the molten zinc particles form a barrier on the blasted surface. Metal Spraying does not require any holes to be drilled into the subject before spraying and eliminates any risk of distortion or build-up of materials in certain areas because of the ability to control the coating thickness. Metal Spray equipment is used in numerous applications, including, but not limited to: enhance and repair engines, cylinder block deck restoration, drivetrains and bodywork in both old and new vehicles. The process is also used for body panel repair in which actual metal (not bog) is used to repair rusted/damaged body panels with Metal Spray equipment. The diversity of Metal Spraying applications is testament to why the process is used all over the world in the automotive industry.
Components
Aluminium Multi-Void Fin Tube
Aluminium multi-void fin tube for the cooling system allows the tube to be soldered when coated with Zinc.
Brakes Shoes & Disk Rotors
The engine system has seen the Metal/Thermal spray process solve a lot of issues, for example better performing and longer lasting brake components:
- Brake shoes suffer rapid wear but this is controlled when a plasma sprayed coating is applied making the shoes last longer.
- Improved brake performance, weight reduction and longer life is given to brake disc-rotors that suffer from an inconsistent friction coefficient.
Cam and Crank Shafts
Reclamation of cam and crankshafts using Plasma, Arc, Powder Flame or Flame Spray Equipment.
Car Panel Repair
Automobile body pressings are susceptible to various types of minor damage during production, handling and whilst creating sub-assemblies.
Metal Spraying using the Arc Process provides a fast, reliable and economic solution to repair these pressings.
Metal spray can be used in production repair of automobile body pressings and assemblies, including window frame joints, roof & quarter panel assy and roof & quarter panel sub assy to wings.
Cylinder Bores
Cylinder bores use plasma sprayed Molybdenum and Ferritic materials to eliminate the requirement of heavy cast iron linings.
Gear Box Reconditioning
Gearboxes are reconditioned using the Arc Spray process.
Gear Selector Forks, Clutch Disks and Synchroniser Rings
Gear selector forks, clutch disks and synchroniser rings suffer from wear so the application of a Molybdenum coating delivers high resistance to scuffing as well as constant friction coefficient for more precise gear selection.
Piston Rings and Crowns
- Piston rings have high wear resistance and less friction when coated with Molybdenum.
- Piston crowns gain improved engine efficiency and extended life when a thermal barrier coating is applied.
Steel Clutch Levers
Steel clutch levers can be reclaimed using the arc, powder flame or flame spray process.
Clutch Pressure Faces
Clutch pressure plate casting faces have been reclaimed by the arc spray process for well over 10 years, on a fully commercial basis, by clutch re-manufacturing specialists.
Gear Box Synchro Rings (Synchromesh Gears)
Gear box synchro rings are subject to considerable wear during the life of a tractor unit and David Brown Tractors Limited are using a Molybdenum sprayed synchro ring to improve the components resistance to wear.
The photograph shows on the right a synchro ring prior to metal spraying and on the left a synchro ring after metal spraying with molybdenum. Not only is the molybdenum extremely slow to wear but also it preserves its surface characteristics throughout its entire life. The metal spraying of these components is normally carried out on a continuous automatic plant using Plasma or Flame Spray systems.
Other sprayed components include, but are not limited to: turbocharger housings, valve guides and stems, shift forks, cylinder liners, engine blocks, connecting rods, exhaust sensors, alternator covers, exhaust pipes, shock absorbers.
Body Panel Repair
Reason for use: Repairing and protecting vehicle body panels.
Metallisation Flame Spray equipment is the preference for classic Volkswagen specialist repairers Vanshack Ltd (UK). The Flame Spray equipment is used for repairing and protecting the vehicle body panels of its customers’ vehicles.
Vanshack provides a range of services including servicing, engine rebuilds, engine re-specification, MOTs, body repairs and customisation to VWV customer’s vehicles and have introduced metal spraying with zinc to their range of services.
Vanshack has chosen the Metallisation MK73 Flame Spray system to metal spray zinc to both the vehicles of VWV customers, as well as other makes of classic vehicle body panels. Vanshack uses the system for vehicle body repair and conservation, using Flame repair for the restoration of peppered panels, Flame fill as a lead loading replacement, Flame seal for seam sealing, Flame coat for anti-corrosion protection and Flame build for component restoration.
Flame Sprayed Zinc
Metal spraying involves the projection of small molten particles onto a blast prepared surface. Upon contact, the particles flatten onto the surface, freeze and mechanically bond, firstly onto the blasted substrate and then onto each other, as the coating thickness is increased. To create the molten particles, a heat source, a spray material and an atomisation/projection method are required.
In the Flame Spray process a wire is fed by a driven roller system through the centre of an oxygen-fuel gas flame where it is melted. An annular air nozzle then applies a jet of high-pressure air, which atomises and projects the molten material (in this case, zinc) onto the vehicle panel surface.
For Vanshack, Flame Spraying zinc onto a peppered body panel is a revolutionary way of restoring and protecting original panels, to ‘conserve the original’. Traditional methods would mean the damage would have to be cut out and replaced but now, using metal spraying, zinc is sprayed over the exposed perforations, replacing what has been lost. In some cases, where the holes are quite large, a support panel or tape is applied behind the open holes to aid the build up of zinc. The zinc will not bond to the support panel or tape, which is simply removed after the repair is complete. The Vanshack Team refers to this as Flame repair.
Body panel before and after Metal Spraying.
Flame Filling is also used by the team, as an alternative to Lead Loading in body filling repair work. This enables car panels to be filled without the risk of heat distortion, which can be created by Lead Loading.
The metal spraying process has made the skills required for Lead Loading much easier, however, this still requires a trained and experienced body repair technician to finish the panel to the highest standards.
In addition, if a panel or section has to be replaced, the team now uses the metal spraying process to load the joins of the panel. A custom coach-works would melt lead into the seam, which is a highly skilled process that can cause heat distortion and is difficult to control in complex and vertical seams.
Seams traditionally would have been sealed using mastic in production cars, which is less robust and more unsightly than metal spraying with zinc. The zinc also offers additional anti corrosion properties, in the repair and seam areas, that are vital to the longevity of the vehicles the Vanshack Team works with. The Vanshack Team refers to this as Flame Seal.
Metal spraying is an excellent alternative to galvanising when spraying entire car panels, Flame Coat provides a good base for the final paint coating to be applied. There are no heat distortion issues, associated with galvanising thin panels, and the coating can be applied in localised areas or over the whole panel. Once the panel has been metal sprayed, Vanshack then applies an appropriate paint coating to the highest standard set by professional coach-works companies.
Crankshaft Reclamation
Reason for use: Repair of worn, mis-machined or obsolete crankshafts.
The reclamation of crankshafts (and many other components) by plasma spraying can produce considerable savings over the replacement cost. 50% savings are common and on large components, as much as 90% may be saved.
The need for reclamation may be to correct manufacturing errors, to repair an obsolete part or a part that has worn excessively in service.
Wherever used, crankshafts can be reclaimed using Metallisation plasma, flame and arc spraying equipment and materials.
Equipment: In this case Arc Spray Equipment was used.
Bond Coat
MSSA 75 Arc Bond - Specially formulated Arc spray Bonding Wire, which exotherms during spraying, producing a very high bond strength coating.
Main Deposit
MSSA S2 - The general purpose material for reclamation or O.E.M. work, giving hard, low shrinkage coatings that exhibit work hardening properties and provide good corrosion resistance.
Inspection
- Check for cracks by ultrasonic or magnetic crack detection method.
- Check for longitudinal distortion.
- Check dimensions accurately for wear, uniformity or wear and particularly depth of grooves.
- Check for signs of overheating.
- Check for signs of nitriding.
- Check technical data for the specific crankshaft with particular reference to the type of bearings in which it is to run.
Note: Crankshafts having the following defects are not recommended for treatment by arc spray: Cracks, distortion, wear below final re-grind tolerance. All traces of nitriding should be removed during pre-machining refer to a) and b).
It is reported that crankshafts running in aluminium tin bearings have exhibited ‘pick up’, therefore caution should be exercised when this type of bearing is being utilised.
Cleaning
- Steam clean if equipment available.
- Degrease by solvent vapour if equipment available.
- Pay particular attention to oilways and ensure removal of all contaminants during a) and b).
- Carry out final inspection.
Pre-Machining
- Grinding wheel type N° 46 Grit Blue V Grade.
- The grinding wheel corners should be dressed to a radius, which matches the radius of the crankshaft fillet.
- Dry grind to remove minimum amount of original metal ensuring that you maintain manufacturer’s minimum recommended diameter.
- Shallow grooves not exceeding 0.1mm (0.004”) in depth are acceptable in the pre-machined surface. Provided that the area can be properly gritblasted.
- Whilst bond coatings will adhere to carburised or induction hardened surfaces, they will not bond to nitrided layers. All nitriding must be removed before spraying.
Cleaning
- Degrease by solvent vapour process if equipment available.
- All particles of abrasive and ground metal retained on ground surface should be removed by careful brushing or momentarily applying adhesive tape.
- Check that all oilways are free from contamination and debris.
Preparation
- Mask all machined surfaces adjacent to the area requiring treatment with a heavy-duty masking tape.
- Plug oilways with tapered, heat resistant, rubber plugs. This plug should protrude equal to finished ground deposit thickness.
- Thoroughly inspect for contamination prior to blasting.
- Thoroughly blast with clean N° 30-36 grade aluminium oxide grit. The standard of surface cleanliness required is as Swedish Standard SA3.
- Ensure that radius at each end of bearing surfaces are thoroughly blasted.
Masking
- Apply No Bond masking fluid using a small brush to all areas adjacent to the area being sprayed. Ensure fluid is not applied to the area being metal sprayed. Small amounts of masking fluid on the area to be sprayed can be removed with an emery cloth.
- Check thoroughly that the area to be sprayed is free from contamination.
Important: The areas to be sprayed should not come into contact with oil, grease, hands or any other form of contamination. Delays between blasting and spraying must not exceed 20 minutes.
Bonding
- The Arc Spray equipment should be set up in accordance with the MSSA manual for spraying MSSA 75 Arc Bond Wire.
- The area to be sprayed should be cleaned with a vacuum cleaner or clean air blast to remove any loose particles of grit.
- Apply MSSA 75 Arc Bond Coat to a depth of 75-100μm (0.003”-0.004”) using multiple passes. Ensure radii are evenly coated.
Spraying Parameters:
- Range: 10cm (4”)
- Nozzle Air Pressure: 3.7 bar (55 psi)
- Voltage before spraying: 38V
- Voltage during spraying: 34V
- Amperage: 200A
Note: Parameters may differ in accordance with type and length of power cables used.
Main Deposit MSSA S2 (to be applied immediately after Bond Coat)
- The arc spray equipment should be set up in accordance with the MSSA manual for spraying S2 Wire.
- Apply S2 final deposit to the specified thickness including grinding allowance i.e. finished ground dimension plus: 0.40-0.50μm (0.0016”-0.002”) grinding allowance.
- The crankshaft should be rotated to give a minimum surface speed of 18m/min (60 ft/min).
- The arc spray pistol should be traversed by hand to give an even coverage ensuring that the radii are also evenly covered.
- Using pre-set callipers check final sprayed deposit thickness to ensure there are no areas below finished sprayed diameter.
- Remove loose particles on surface with wire brush or clean air blast.
- Allow to cool thoroughly preferably whilst rotating.
Spraying Parameters:
- Range: 15cm (6”)
- Nozzle Air Pressure: 4.3-4.6 bar (65-70 psi)
- Voltage before spraying: 38V
- Voltage during spraying: 35V
- Amperage: 250A
Sealing
- Apply Sprayseal “M” in accordance with Metallisation Sprayseal “M” instructions. Keep surface wet by re-application for a period of approximately one hour.
- Allow to dry thoroughly.
- Remove uncured sealer from surface with clean, disposable cloths or paper towels.
De-Masking
- Remove all masking tape.
- Remove all overspray thoroughly, taking care to prevent coating damage.
- Remove all traces of No Bond with solvent.
Finish Grinding
- Grinding wheel type N° 46 Grit Blue V Grade.
- Dress grinding wheel to match radius of crankshaft fillet.
- Wet grind to final diameter taking light cuts using feeds and speeds in accordance with grinding machine manufacturer’s instructions.
- Remove rubber plug from oilway and chamfer hole by hand grinding with profiled stone or rotary file.
Inspection
- Check dimensions.
- Check for cracks or defects in sprayed coating, i.e. large pores or protrusions and loose particles.
- Clean to remove all traces of grinding abrasive and loose particles.
Polishing
- Set the crankshaft in a lathe to rotate in the same direction that it will rotate when assembled in an engine.
- Polish finished ground area until the shaft is highly polished.
Finish Cleaning
- Clean the crankshaft thoroughly to remove all contamination, including any grinding debris retained on bearing surfaces.
- Check all oilways are clear.
- Wash with petroleum spirit/paraffin.
- Dry all bearing surfaces with clean, disposable cloths or paper towels.
- Final inspection prior to packing.
- Wrap in clean polythene sheet.
- Pack and despatch.
Note: Prior to installation in engine, repeat procedure – ‘Finish Cleaning’ a) – d). clean engine oil to fill any remaining porosity.
Clutch Diaphragm Springs Reclamation
Reason for use: During use, the clutch diaphragm spring will wear on its tip ends at the point where it comes into constant contact with the thrust bearing.
The clutch diaphragm spring in itself is not particularly an expensive item, however, the labour involved in removing the old spring from its housing then replacing it with new will push up the total cost of clutch refurbishment.
By using the Metallisation flame spray process, it is possible to apply a coating of molybdenum onto the work area of the diaphragm spring without removing it from the housing. This makes the spring re-serviceable at a fraction of the replacement cost.
Metal spraying molybdenum, using the Metallisation flame spray equipment, gives the unique ability to produce a range of coatings between 250 and 800 HV. This makes it possible to hard face diaphragm springs, giving them added lubrication and valuable extended life.
Equipment: Metallisation MK61 Flame Spray System
Materials: Molybdenum Wire
Preliminary Inspection
- Springs worn below final regrind tolerance should NOT be sprayed. Sprayed metal deposits do not impart any strength to the base material.
- Components should be checked dimensionally and for cracks or any other major faults.
Preparation
- Degreasing. Any approved industrial solvent may be used to completely remove grease or oil from the surface.
- Preliminary Machining. Grinding or finishing may be used to remove any major scoring on spring tips blending in to form a uniform concentric base.
- Mask surfaces adjacent to area requiring treatment with a heavy duty masking tape.
- Thoroughly inspect for contamination prior to blasting.
- Thoroughly blast with clean Nº 30-36 Grade Aluminium Oxide Grit.
Application of Sprayed Coating
- Masking.
- Apply No Bond masking fluid using a small brush to all areas adjacent to the area to be sprayed. Ensure fluid is not applied to the area being sprayed (small amounts of masking fluid on the area to be sprayed can be removed with an emery cloth).
- Thoroughly check the area to be sprayed to ensure it is free from contamination.
- Important: The area to be sprayed should not come into contact with oil, grease, hands or any other form of contamination.
NOTE: Masking is not always required when spraying diaphragm springs.
Spraying
Spraying should be done as soon as possible after preparation and before any visible sign of deterioration occurs. The diaphragm spring in its housing should be mounted on a turntable having a surface speed of not less than 18 metres/minute (60 feet per minute).
Bond Coating
A deposit of molybdenum wire is applied to a deposit thickness of 0.05mm-0.15mm (0.002″-0.006″) at a range of 75mm (5″). The spray stream should be at 90º to the surface being coated and traversed by hand to give an even coverage over the area being refurbished.
Main Deposit
- Continue to spray the main deposit of molybdenum, using the same spraying parameters as the bond coat, but increase spray range to 100mm-150mm (4″-6″).
- Complete the spraying of the main deposit traversing the spray head to give a uniform coating over spring tips.
- The final deposit thickness will depend upon the condition of the spring prior to spraying and should be adjusted accordingly.
Spraying Parameters - Metallisation Mark 61
Molybdenum Wire
Acetylene Pressure: 1.03 bar / 15 psi
Oxygen Pressure: 1.9 bar / 30 psi
Air Pressure: 4.5 bar / 65 psi
Flowmeter Pointer Settings: Gas 5.5 / Oxygen 2.25
Finishing
Under normal circumstances it is possible to use the component in the ‘as sprayed’ condition without any problems, but for cosmetic purposes, a light polish may be required.
Ford Motor Company Refurbishing Old Engines using Plasma Spray
When an engine fails or becomes very worn, it is usually pulled from the vehicle and scrapped. Ford wants to change that by utilizing a high-tech plasma process to re-manufacture broken engines. The process reduces carbon emissions by about half when compared to making a new engine to replace the old one, and results in a like-new engine block. (Extracted from an industry article shown at https://newatlas.com/ford-plasma-engine/40728/ )
Exhaust Systems Thermal Barrier Coatings
Reason for use: Applied to vehicle components to reduce heat transfer and improve vehicle performance.
Thermal Barrier Coatings (TBCs) consist of ceramic materials which are widely used on vehicle exhausts, turbocharger casings, heat shields and other vehicle components to reduce heat transfer and improve vehicle performance. Heat soak from hot exhaust systems transfers into other vehicle components causing reduced performance or damage. Thermal Barrier Coatings (TBCs) are used in motorsport and on high-performance vehicles to reduce this effect.
The TBC's give two benefits: Keeping the heat in the exhaust system reduces under bonnet temperatures and also keeps the heat energy in the exhaust gas, which improves the thermodynamic performance of the turbocharger. Both effects enable more power to be produced and improve reliability.
The Thermal Barrier Coating system is applied with a Powder Flame Spray Pistol. The Thermal Barrier Coating is typically a two part process with a bond coat of Ni/Al or Ni/Cr type layer and a top coat of a suitable ceramic.
Powder flame applied Thermal Barrier Coating’s are an excellent solution for the majority of exhaust related applications. However, for extreme performance applications, the thermal barrier coatings can also be applied by the plasma spraying process, producing coatings that are denser and with higher bond strengths than with powder flame spray.
Ceramic powder spraying of exhaust manifold.
Plasma ceramic coating containing magnesia/zirconia on exhaust manifold.
Ford GT.40 Sports Car
Reason for use: To prevent external surface corrosion.
Two independent exhaust systems, fabricated from steel tube in the Ford GT.40 sports car, have been metal sprayed with 175 microns (0.007”) of aluminium using the latest Metallisation fine spray electric arc techniques. The treatment has been found to be fully effective in overcoming the extremes of heat oxidation and thermal shock from the output of this high performance engine.
Multi-void Aluminium Tubing for AC Condensers
Reason for use: Corrosion protection and brazing during assembly.
Corrosion of heat exchangers for automotive air conditioning units can be a major problem. The unit is often located near the front grille of the vehicle and hence is exposed to a severely corrosive environment, with road salts, rain and high temperatures all contributing to high corrosion rates.
In order to reduce the rate of corrosion, historically several methods have been tried: zinc diffusion by flux brazing, sacrificial anodes of zinc, tin, or indium; chromating and painting. Due to inherent production difficulties, poor corrosion resistance, pollution, restriction in plating and high costs, none of these treatments provide an optimum solution.
Arc Sprayed zinc offers equal or higher corrosion resistance, lower production costs and reduced pollution than other competing processes.
Manufacturing Methods
Multi-void aluminium tubing is used in the production of serpentine-type condensers, widely used in air conditioning systems. The voids in the tubing provide a route for the cooling medium gas/liquid to extract heat from the incoming air. The joining/coating of the tubing and the corrugated fins is generally carried out by flux brazing or zincate nocolok brazing processes. In either case, problems are inevitable, e.g. damage to furnace and jigs by the flux used or increased costs through waste treatment processes.
Advantages of Zinc Sprayed Tubing
- Highly corrosive flux is not required.
- Zincate treatment and waste treatment not required.
- Zinc is deposited at a pre-selected rate, which can be increased or decreased as required.
- A zinc diffusion pattern equally uniform to zincate process is produced.
- Productivity improves.
- Post braze cleaning processes can be eliminated.
Comparison of Zinc Coating Methods on Extruded Aluminium
| Zinc Deposition Method | |||
| Zincate | Electroplating | Arc Spray | |
| Summary of Method | By displacement reaction in a zinc alkaline solution, zinc is deposited on the surface of the substrate. | An electric current is passed through a plating solution containing zinc, held in an electrode in contact with aluminium. The zinc is plated onto the substrate. | Atomised molten zinc is projected onto the substrate. |
| Qty of Zinc Deposited | 5 - 20g/m2 | 5 - 20g/m2 | 5 - 20g/m2 |
| Adhesion (Exfoliation when Bent) | Not Good | Not Good | Good |
| Brazability (by Nocolok Brazing) | Good | Good | Good |
| Zinc Diffusion After Brazing | Good | Good | Good |
| Corrosion Resistance | Good | Good | Good |
| Coating Cost | High | High | Low |
| Advantage of Process | Practical experience in use (well known process) | Uniform zinc deposit, short process time | Low process cost |
| Disadvantage of Process | Long process time, waste water treatment takes time | Control of conditions for plating is difficult | Low levels of zinc dust bi-product |
Arc Spray Method
The zinc coating is carried out ‘in-line’ with the extrusion press. The plant can be installed on to either new or existing lines. The number of individual Arc Spray pistols required is dependent on the number of extrusions being produced by the press, two pistols being used for each tube (one per side). The pistols are located on adjustable mounts, angled to allow even coverage of both flat parallel section and side section of the extrusion. The pistols are located in a spray chamber to contain unwanted dust and this is linked to an extraction/collection system. The chamber contains carbon supports/guides to ensure accurate location of the extrusion relative to zinc spray stream.
Spray Equipment Used
- Pistol – Metallisation Arc Spray 528E, electrically driven pistol and supplies package to feed power and air to the pistol. Length of supplies package varies relative to the installation.
- Power source – Metallisation S250 energiser, rated at 250 amps maximum at 100% duty cycle. Typical spray rates for this application vary from 20-100A.
- Controller – Metallisation 1600I controller, typically externally mounted for ease of integration into the extrusion line control system. Can be integrated into the energiser.
Material
1.6mm diameter, Metallisation 02E, 99.99% minimum purity zinc wire, typically supplied in 250kg drums. Wire can be supplied with leading and trailing ends available to enable joining of wire from one drum to the next, allowing continuous production.
References
SAE Technical Paper: Development of Pitting Corrosion Resistant Condenser with Zinc-Arc-Spray Extruded Multi-Cavity Tubing. Kazunori Ishikawa, Hiroshi Kawase & Hitoshi Koyama – Furukawa Aluminium Co, Ltd
Yoshihara Hasegawa – Nippondenso America Inc. Kenji Negura and Masayuki Nonogak – Nippondenso Co, Ltd presented at SAE International Congress and Exposition, Detroit, Michigan 1991
Brake Drums Reclamation
In Hong Kong, a Metallisation Arc Spray Unit which was supplied to the Kowloon Motor Bus Co. Ltd, is used to reclaim worn brake drums and engineers quickly recognize the significance of this application, as the drums are subject to considerable expansion and contraction from heat during use. The drum is first rough turned and a bond coating of is applied, followed by a deposit of S20/S2 Steel after which the surface is finish turned to size. The application would be impossible with a Flame Spray pistol, the improved cohesion and adhesion of the Arc Spray deposit ensures full adhesion during expansion and contraction.
Piston Rings
Reason for use: To produce a low friction coating, dimensionally stable throughout it's working life.
A piston is defined as a ‘cylindrical piece moving to and fro in a hollow cylinder as in engines or pumps’. To seal the gases during the compression and work strokes of an engine, piston rings are used to provide an effective seal as well as preventing excessive lubrication oil from reaching the combustion chamber and providing a heat conduction path from the piston to the cylinder.Requirements of a Piston Ring.
The piston ring is required to operate in temperatures above 232°C (450°F) with friction free capabilities to achieve in excess of 6000 revolutions per minute, as well as to remain dimensionally stable throughout its working life. More recently, new challenges with respect to performance and durability of piston rings have arisen, due to legislation in various Continents concerning emissions control.These challenges are being faced with the technological improvement of the manufacturing process and the development of new base materials, coatings and ring profiles.
Coating Types
Back in the 1940’s piston rings were mainly Chromium plated for wear resistance. Although still used in the mid 1960’s, this was superseded by the thermal spray process to overcome fretting wear in the chromium plated rings.
Conventional 100% molybdenum coatings are usually sprayed into a shallow channel on the peripheral surface. This method is used to provide a better “grip”, however in many applications, eg. turbocharged engines, where extreme shock loading combined with severe heat exists, this is unable to prevent the material from “flaking off”.
Due to these limitations, continuous research and development of coatings is on-going to provide a coating with properties that would provide even superior engine performance. The net result to date is a “super chromium” called “channel chrome” and a “super molybdenum” applied by the plasma or high velocity oxygen fuel (HVOF) System. Following the application of the thermal spray coating, the time required to deposit the coating and the nature of its application instills a quantity of heat into the mandrel which, due to production times, usually requires cooling by the use of air jets prior to being manually unloaded for subsequent grinding. Grinding of the rings on the mandrel is carried out until the piston ring is revealed leaving the thermal sprayed coating in the ring channel.
Flame Sprayed Piston Rings
Plasma Sprayed Piston Rings
Molybdenum coatings which were plasma applied, overcome the problem of premature coating failure. Protective carrier gases used in the plasma operation reduce the number of oxides formed during spraying and retain the excellent bond strength of molybdenum.Plasma sprayed deposits provide a wide range of compositions that may be used in the design of a piston ring coating. Any material that does not sublime or decompose in the plasma may be sprayed. This includes metals, metal alloys, cermets, oxides and some non-metallics. The constituents may be aggregates or dry blended mixtures of the above materials.
Selections are based on the required properties of the coating. First and foremost for piston ring coatings is the mutual wear compatibility between the ring coating and the cylinder bore.Most often, this decision is based on past experience. Because of its anti-welding properties, besides a good adhesive and cohesive strength, it is a common practice to improve the bond strength of the coating by adding NiCr, CrNiSiB or cobalt. The hard phase is provided by the addition of carbides or oxides.
Plasma sprayed deposits have sufficient strength and ductility to be fully face sprayed on the ring. Full face spraying eliminates the cast iron edges of conventional channel moly, and at the same time minimises the possibility of oxidation by eliminating corners and crevices where oxidation and erosion of the base metal begin.
Elimination of the cast iron edges prevents the possibility of scuffing occurrences under extreme temperature situations.
Brake Disks - Special Coating Increases Abrasion Resistance
An outstanding and unusual example of the sophisticated engineering applications of the metal spraying process is provided by the treatment of the brake discs for the B.S.A. Triumph Motorcycle, which won the Daytona 200 mile race in America.
The functionally beautiful triple cylinder machines have twin disc brakes at the front, which, according to development engineer Doug Hele ‘are the most fantastic brakes on any motorcycle!’ They need to be able to stop 164 Kg (360lbs) of motorbike plus rider from speeds up to 160 mph. A further accolade from Percy Tait who said, after a test run, ‘these brakes are better in the wet than any brakes I have previously used in dry conditions!
’Metallisation come into the picture by applying a special surface deposit on the brake disc, which is made of light alloy to save weight. The deposit has been specially formulated to provide both the necessary abrasion resistance to give braking grip, and also to provide good heat conductivity to aid cooling of the discs under the harsh braking conditions. A unique method of Arc spraying provides the required properties, and this method of treatment has been established after many years of research and development carried out by the Lockheed Hydraulic Brake Co. Ltd., member of the Automotive Products Group in association with the Technical Department of Metallisation.
Dynamometer Rollers
A specially formulated steel and ceramic surface coating has been developed for dynamometer rollers used by garages. The scuffing action of the tyres causes rapid polishing of the roller surface, which reduces the efficiency of the equipment. To overcome this, Suntester Ltd, manufacturers of test equipment and dynamometers have perfected a surface coating, which provides a better gripping surface for the tyre. The process has been developed in association with Metallisation Ltd. The surface treatment takes the form of a sandwich coating on the rough-machined surface of the roller. Molybdenum is sprayed as a bond coating and on top of this S2. This is followed by alumina/ titania and a top coating of S2. The relative sizes of the ceramic and steel particles are such that the ceramic particles fill the gaps in the steel coating. The total effect is a honeycomb of steel packed with ceramic. Good adhesion to the roller surface in shear and resistance to polishing over a long period are specific advantages of this coating.
Vintage Car Chassis Restoration
Image Provided Courtesy of Metal Spray Hungary
Metal Spray Hungary, in conjunction with a classic car restoration specialist completed the restoration of a Ferrari Dino sports car which was brought to them in a weathered condition. As the chassis is the most critical part of a vehicle with regards to corrosion, Metallisation Flame Spray equipment was used to provide a high quality, long-lasting anti-corrosion coating.
The process comprised of grit blasting to achieve a maximum surface quality of Sa3 (to remove the contaminants and any residue), which provided a surface roughness for the Metal Spray coating to bind to. The Metal Sprayed coated was then applied, followed by a two component industrial paint system.
Images Provided Courtesy of Metal Spray Hungary
Videos
Differential Repair
Differential Repair Demonstration using Powder Jet 85.
Car Body Panel Repair
The above video shows body panel repair using flame spray equipment.
For more information on Metal Spray equipment or consumables, call us on 07 3823 1004, or email us using our contact form.
