Worn components can be extremely costly in a production environment where downtime needs to be kept to a minimum. Components/parts can be salvaged using the Metal Spray process by restoring the dimensions of the damaged part, which in turn can reduce costs. Having to source and then pay for costly replacement parts is then avoided as well as long waits for delivery! Well selected coatings often perform better than a new component.
Typical applications include machine shafts and spindles, rotating and reciprocating shafts, automotive and machine crankshafts, roller faces and journals, hydraulic rams, pump plungers and many more!
Hard-facing is commonly used to prolong the life of earth-moving equipment as well as being used to repair equipment components. By applying a harder material on top of the parent metal, it extends the life of the component which in turn saves maintenance costs and downtime. For more on Hard-Facing, Click Here.
Front Strut Reclamation
Mining truck suspension system components can be reclaimed with the Metal Spray process.
The below image shows a front strut for the suspension system being reclaimed with the HVOF process.
Wheel Spindle Reclamation
Mining truck wheel spindles can be reclaimed using the HVOF process.
The wear and tear on the expensive underground equipment used by the mining industry is very considerable indeed, particularly at the coal face where mammoth automatic cutters have taken over from the miner.
An example of wear on the machinery is provided by the main drive head shafts of the coal rippers. One end of the shaft carries the drive, and the other end carries the 1.524m (5ft) diameter cutting head which rips into the coal seam at the face. The drive shaft is keyed to accept the cutting head mechanism and it is at this point that the wear is most severe. The photograph shows the size and position of the keyway clearly. Wear takes place around the bearing circumference and particularly at the keyway edges (which carry the full weight and impact shock of the cutting heads). In the metal spraying rectification of these shafts, any wear of the actual keyway is repaired first of all by re-welding and re-cutting to standard size. The surfaces of a number of such shafts have been reclaimed. A deposit of S2 1.5mm (0.060”) thickness has been applied using the Metallisation Arc Spray system.
Rear Jack Assembly Piston, Hydraulic Motor Piston and Arcing Cylinder Piston Rod
Three examples of components of a Dosco Miner Machine that has been successfully reclaimed using a Metallisation Flame Spray Pistol in the Central Workshops of the NCB at Midlothian,UK.
From left to right the components are – A rear jack assembly piston, a hydraulic motor piston and an arcing cylinder piston rod. All the components have received a bond coating of followed by a final deposit of either S2 or 80E.
Caterpillar V12 Engine Block Reclamation
Waste Water Pumps
Pump Sleeve as Shown in Service
Industry: Waste Treatment
(Left) Worn Sleeve that has been taken Out of Service. (Right) Worn Area to be Repaired with Rokide® "C" Coating.
The treatment of waste water involves pumps operating 24 hours a day under very demanding conditions. The water used to transport abrasive solids is corrosive in nature, making pump maintenance a considerable drain of both time and money.
The normal mode of failure is leaking from the gland area as a result of wear and corrosion of the shaft. This can be overcome short-term by tightening of the packing gland, but, over time the leak path redevelops, leading to the pump being removed for overhaul.
One simple solution has led to major reductions in downtime and the associated cost savings by utilising Rokide® "C" (Chrome Oxide) to coat the pump shaft sleeves.
For this application, Rokide® "C" ceramic spray coating was recommended.
The parts are coated and then finished to a 16 to 17 RMS. The treatment plant where this application took place now has 14 of their 19 pumps coated with Rokide® "C". The first of the Rokide® "C" coated pump sleeves put into operation was still working well through continual use in its fourth year. The plant coat the balance of their pump sleeves when they need to be repaired.
Rokide® "C" Coated Sleeve Installed into Pump Assembly. Sleeve has been Coated and Ground to Achieve Dimensional Fit and Finish.
This application has prevented downtime and pollution control in waste water treatment plants.
Laser Cladding for Critical Component Repair - Duplex Stainless Steel
Laser cladding, a process that falls into the range of hard-facing solutions, can be used to increase corrosion resistance, wear resistance or impact performance of metallic components, using a method of applying a fully dense, metallurgically bonded and virtually pure coating.
Laser cladding can be used across a diverse range of industries. In this instance it was used to repair an EN8 steel drive shaft from a large CNC boring machine. The steel drive shaft had become worn in two bearing areas and was considered ‘unweldable’ by standard methods. Due to the critical dimensions of the shaft, and its relatively small size, it was crucial that distortion had to be controlled.
The Laser cladding process was an ideal solution for the EN8 steel drive shaft, as it produces a coating with a higher level of purity than other traditional welded hard facing processes. Also, the very low heat input, associated with a laser, minimises distortion and results in a refined microstructure.
Materials - Main Deposit: Duplex stainless steel
Preparation: Clean the worn bearing areas with alcohol to remove grease.
Equipment: Metallisation MET-CLAD system
Application of Laser Cladding
The two worn surface areas of the EN8 steel drive shaft were laser clad with duplex stainless steel and machined back to their original dimensions, enabling the shaft to be returned to the CNC boring machine. The laser cladding process utilises a precisely focused high power laser beam to create a tightly controlled weld pool into which a metallic powder is applied. The powder is carried by a stream of inert shielding gas, which is blown coaxially through the laser beam. The highly controllable nature of the laser beam allows fully dense cladding with minimal dilution and a perfect metallurgical bond. Due to the high level of accuracy and control, laser cladding enables the cost effective application of high performance alloys to tackle a wide range of engineering issues. Typical deposition rates are between 60 and 100 g/min around 3-6 kilograms per hour, depending on the material being deposited and the geometry of the work piece.
To apply a laser clad coating the cladding head has to be fed with four key things; a laser beam, process gasses, the metallic powder and cooling water. The Metallisation MET-CLAD laser cladding control console provides integration and control of the complex component parts. The MET-CLAD system is a simple to use control system with touch screen HMI and is based on the Metallisation HVOF and Plasma control concept. Using laser cladding to repair the EN8 steel drive shaft was the ideal solution, as the repair had to be of a high strength due to the load bearing pressure placed on the working component. The chemistry of the shaft was unsuitable for a traditional welding process due to its high carbon content and it was crucial there was absolutely no distortion. Finally, the low heat input associated with a laser clad coating, had a minimal effect on the base material strength.
Laser cladding is capable of producing coatings with a combination of excellent toughness and abrasive wear resistance and is ideal for Critical Component Repair work. In this instance, due to the low heat input in the laser cladding process, the duplex stainless steel and the EN8 steel drive shaft remained intact, without distortion. A critical requirement in this type of project.
Reclamation of Hydraulic Rams (Cylinders)
Reason for use: Repair of worn and damaged rams.
The hydraulic industry, like any other industry, has its share of wear problems. These are generated by the very harsh operational conditions. The MSSA 95 arc spray coating offers the advantages of low friction and great wear resistance, with the added benefit of being able to repair deeply scored rams with one process.
By using the arc spray process, it is possible to apply a coating of MSSA 95 onto the worn areas of the hydraulic ram. This brings them back up to the original size at a very small percentage of the replacement cost, enabling the ram to be back in service in a very short period of time.
Equipment: Arc Spray Systems
Not always required.
MSSA Chromex 20 Wire: Arc spray bonding wire exotherms during spraying, which produces very high bond strength coatings.
MSSA 95 wire: Coatings are hard and exhibit work hardening properties. Because of its low shrinkage, residual stresses are low and deposits of considerable thickness may be sprayed. The high chromium content provides good corrosion resistance.
- Degrease by solvent vapour process, if equipment available.
- Inspect for longitudinal distortion, cracks or faults taking the ram below the manufacturers recommended operating tolerances.
NOTE: Metal sprayed deposits do not impart any strength to base materials.
- Degrease by solvent vapour process, if material available.
- Check all surfaces are free from contamination and debris.
- Mask all machined surfaces adjacent to the area requiring treatment with heavy duty masking tape.
- Thoroughly inspect for contamination prior to blasting.
- Thoroughly blast with clean Nº 30-36 Grade Aluminium Oxide Grit.
- Ensure that areas to be treated are thoroughly blasted, paying particular attention to edges of machined areas.
- Apply No Bond masking compound using a small paintbrush to all areas adjacent to the area being sprayed (small amounts of masking on areas to be sprayed can be removed with emery cloth).
- Thoroughly check the areas to be sprayed for contamination.
Important: The areas to be sprayed should not come into contact with chains, rope slings, hands or any other form of contamination. Delays between blasting and spraying should not exceed 20 minutes.
- Electrical supplies are generally more readily available.
- Potentially flammable and explosive gases are not required.
- The arc spray equipment should be set up in accordance with the MSSA Manual for the spraying of MSSA Chromex 20 Arc Wire.
- The areas to be sprayed should be cleaned with a vacuum cleaner or clean, dry air blast to remove any loose particles of grit.
- Apply MSSA Chromex 20 bond coat to a depth of 75µm-100µm
- The hydraulic ram should be rotated to give a minimum surface speed of 18 metres/minute
- The arc spray pistol should be set so that the spray stream is at 90º to the surface being coated and traversed at an even speed, giving a uniform coating.
- Spraying Parameters Bond Coat
- Range: 100mm (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 and hoses being used.
Main Deposit MSSA 95 (to be applied immediately after bond coat)
- The arc spray equipment should be set up in accordance with the MSSA manual for spraying MSSA 95 (Iron Chrome Boron) Wire.
- Apply final deposit to the specified thickness, including grinding allowance, i.e. finished ground dimension plus 0.375mm-0.5mm (0.015”-0.020”).
- The hydraulic ram should be rotated to give a minimum surface speed of 18 metres/minute.
- The arc spray pistol should be set so that the spray stream is at 90º to the surface being coated and traversed at an even speed to give a deposit of not more than 0.13mm per pass.
- 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.
- Spray Parameters - Main Deposit MSSA 95
- Range: 15cm (6″)
- Nozzle Air: 4.3-4.6 bar (65-70 psi)
- Volts before spraying: 32V / Volts after spraying: 30V
- Amperage: 150A
- 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 all uncured sealer from the surface with clean, disposable cloths or paper towels.
- Remove all masking tape.
- Remove all overspray taking care to prevent coating damage.
- Remove all traces of No Bond masking compound with solvent.
- Grinding Wheel Type Nº 46 Grit Blue V Grade.
- Wet Grind to finished diameter, take light cuts using feed and speed in accordance with grinding machine manufacturer’s instructions.
- Check dimensions.
- Check for cracks or defects in sprayed coating, i.e. large pores or protrusions and loose particles.
- Clean to remove any traces of grinding abrasive and loose particles.
- Wash with petroleum spirit/paraffin.
- Dry the surface with clean, disposable cloths or paper towels.
Chevron Plunger Pump - Kermetico Case Study
This case study is about a three piston plunger pump used to pump “gack”. Gack is a term used to describe a substance that has a variable composition and is generally bad for the equipment it comes in contact with, particularly pumps. In this case the gack consisted of water and various unspecified and unknown petroleum products and byproducts with varying amounts of particulate.
The first time we saw the plungers was October 4, 2011. The set of three arrived with a NiCrBSi fused coating applied by others. We were told that the plungers had been in service for only a year. Here is what they looked like:
The scoring was from “mystery” particulate trapped between the plunger and the packing. This led to leakage and the need to repair them.
We ground off the old fused coating and found that one of the three had to be taken well below finished dimension in order to remove all of the original coating. In order the keep the price of the job within reason we first built up a layer of NiBSi 0.45 mm (0.018”) thick followed by a layer of tungsten carbide cobalt chrome (86-10Co-4Cr) 0.40 mm (0.016”) thick, which was finished ground back to 0.25 mm (0.010”) thick per side.
The other two were coated with only tungsten carbide and finished to a thickness of 0.25 mm (0.010”) per side.
Below are how they looked during and after processing, ready to go back into service:
That was the last time we saw them until March 24, 2016, when two of the original three were returned for re-servicing.
Here is what one of the two returned plungers looked like after 4.5 years of service.
The first plunger failed because the seal (packing) lost lubrication and the plunger overheated severely. This was the plunger that required a layer of Ni to reduce the thickness of carbide applied. The carbide failed at the Ni layer. The second plunger also lost lubrication but much later than the first one. The defect you see is from ‘gack’ under high pressure escaping from under the seal and eroding the coating much like high pressure water jetting.
The third unit did not have a lubrication failure and is still in service. Measurements of the failed plungers in areas where there is no erosion or coating failure due to overheating are IDENTICAL to the finished dimensions when they left our shop in 2011!
Zero wear suggests that if the lubrication system hadn’t failed these plungers would have been in service for many more years.
The sleeves that hold the packing that these plungers ride in have pretty much the same story. Two of the three failed and the one that didn’t have lubrication problems is still in service. We will be coating the ID of those two and they will become spares.
The two sleeves in for repair did have a little less than 0.001” of measurable wear in the area where the packing sits. The wear was caused by the packing getting loose and moving with the piston. There is also evidence of some ‘water jetting’ damage as well.
And the best part is that the coating of 86-10-4 that we are applying today is significantly better that the coating that was applied to these plungers. Back then the hardness was in the range of 1350-1375 Hv300, and today it is in the range of 1450-1500 Hv300.
Crane Wire Barrel
During final machining one section of this crane wire barrel was accidentally reduced by 12.5 mm (½”) beyond the required diameter. It was impossible to reduce the rest of the barrel to the same diameter because of the strength factor. Metal spraying was used to build up the surface of the mis-machined area back to the originally specified diameter. A continual groove was then machined into the barrel to accept the feed of the wire rope. The Metallisation Arc Spray specification was – a bond coat followed by a build up of S20 to the required thickness, i.e. a 6.25mm (¼”) on the radius. It will be appreciated that the service conditions in which the barrel operates together with the constant squeezing action of the rope places a considerable load on the metal sprayed deposit; the surface has stood up to the treatment in a perfectly satisfactory way.
Electric Motor Armature
This photograph shows an electric motor armature reclaimed on the journal area. The work was carried out using a Metallisation Arc Spray Unit and a deposit of 2.54mm (0.100”) of S2 was applied. The repair was completed in approximately 36 hours as opposed to a delivery period of several months for a new unit. The cost of reclamation was about 1% of the cost of replacement.
Fork Lift and Earth Mover Brake Drum Clutch Housing
Fork Lift Brake Drum and Earth mover brake drum clutch housing were repaired using a Metallisation Arc Spray system depositing S20 Steel.
For more information on Metal Spray equipment or consumables, call us on 07 3823 1004, or email us using our contact form.