Engineered Surfaces for Exceptional Performance
Engineered Surfaces for Exceptional Performance

Caterpillar Cylinder Block - Video provided courtesy of IR4 

Vehicles (bulldozers, Caterpillar trucks, loaders) and machinery (drills, hoppers, trommels, trams) used in the mining industry are subject to dramatic wear degradation. Mining processing plants utilise large crushers, mills, reactors, roasters and other equipment which are also subject to extreme wear and corrosion. This degradation can be reduced or mitigated through the use of Metal Sprayed coatings. Components can also be refurbished to OEM standards by restoration of dimension techniques.

Video provided courtesy of IR4 

Components that are Metal Sprayed for Protection Include

  • Hydraulic Rods.
  • Spindles.
  • Rotors.
  • Shafts.
  • Stators.
  • Anchor Brake Set CAT 793.
  • Caterpillar Cylinder Blocks.

Lignite Mining Tools

Industry: Lignite Mining.

Principle of the Process: Extraction of the lignite, carrying of the lignite, transfer of the lignite.

Equipment Concerned: The application with TufCote® G-A 8mm ⌀ (even 6.35mm) products concerns mainly the extraction and treatment phases of the lignite (refer to pictures): Teeth of bucket, extraction conveyor, hopper, scrapper.

Service Conditions

  • Ambient temperature ~20°C to 50°C.
  • Abrasion and erosion lignite.
  • Risk of medium shocks.

Problem: Tools are subject to severe abrasion resulting from the minerals.

Coating Solution: Abrasion Resistant Coatings TufCote® Grade A 8mm ⌀: tungsten carbide with a metal matrix. 5 to 6mm thickness are required.

Benefits of the TufCote®: 

  • Lifetime is 6 to 7 times more than lifetime with special steels.
  • No capital investment is required to apply the TufCote® brazing flexible cord (only a flame torch is required).
  • Possible application on site or in job shop.
  • TufCote® application procedure is easy to learn,
  • TufCote® can be applied on construction steel (the hard steels, or special and expensive steels are not required).
  • Possibility to rebuild on a coating previously welded.
  • Coarse and angular tungsten carbide grains, for better resistance to abrasion (TufCote® Grade A).

TufCote® GRADE A Product Specification:

  • Self-fluxing alloy matrix: 37 to 40% in weight
  • Tungsten carbides: 60 to 63% in weight
  • Particle size: Grade A within 0.1 to 1.6 mm (10–150 mesh)
  • PackagingTufCote® is supplied as a continuous flexible cord, on spool.
    • Available in 4.75, 6.35 or 8mm ⌀.

Coal Ripper Main Drive Head Shaft

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.

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.

Caterpillar V12 Engine Block Reclamation

The above image shows a Caterpillar V12 Engine Block being Arc Sprayed with proprietary coating to original. Final machining was completed by milling.

Hydraulic Pit Props

The photograph shows several of these components, each of which measures 1.5m (5 feet) long by 15.24cm (6 inches) in diameter. They have been sprayed with a deposit of S2 with a finish thickness ranging from 0.4mm (0.016”) to 1mm (0.040”). The new surface offers the advantages of reduced friction and greater wear resistance. The photograph shows the components before finishing; the work was carried out using a Metallisation Arc Spray system.

Slurry Pump - Case Study

HVAF equipment is utilised to protect slurry pumps' wet parts from erosion and abrasion as a result of hard solid particles. The HVAF coatings extend component life which in turn enables longer mean time between failures and significantly reduces maintenance costs.

A slurry is a mineral feedstock to be processed in a mining concentrator plant or a waste stream of tailings including hard particles. In oil and gas refining, slurries are usually catalyst streams, including limestone or zeolites. Under unfavourable circumstances of corrosive media, the combined effect of corrosion and erosion can lead to dramatically increased wear rates.

The mechanical and chemical forces are extremely demanding for the material integrity of pump parts — especially when temperature, pressure or flow volume increases.

Background: A customer asked us to coat a slurry pump backing plate to protect it from the abrasive slurry passing through the pump. The slurry consists of gypsum, aluminum oxide and water. The impeller came from the manufacturer already coated with tungsten carbide, presumably by a HVOF process. The pump housing was uncoated and the customer didn’t want the housing coated as, in previous experiences with this pump in this particular application, the backing plate was the only part adversely affected by the pumped slurry. 

Results: Figure 1 shows the backing plate with the applied HVAF tungsten carbide coating after one year of service.

After measuring the coating thickness, we found that the thickness after one year of service was identical to the original applied coating thickness. As we began to examine the backing plate we found an interesting area (see Figure 2).

The backing plate seal to the housing wasn’t absolute and some erodent made it past the coated surface of the backing plate and eroded material from under the coating. It is hard to see in the photo but the coating is undercut and is still intact forming a sharp overhang of coating. Figure 3 shows a close up of the eroded area.

The other main parts of this slurry pump didn’t fare as well. The impeller shown in Figure 4, lost much of the applied coating and the blades were wearing away fast. If the pump didn’t begin leaking the impeller would have failed after little additional service. In the close-up view you can see where the HVOF coating has completely gone (Figure 5). In those areas where the coating is worn away, the metal is being worn away quickly due to the blades being significantly shorter than the adjacent blades that still have coating remaining on the surface. This can be seen using a straight edge and a little back lighting (Figure 6).

The pump case didn’t do well either. Here is a look at it as received (Figure 7). 

The damage is readily apparent in Figures 8, 9 & 10, where closeup views shoe the extent of the damage.

The customer decided that the best course of action was to line everything with a WC-10Co-4Cr tungsten carbide coating, applied with a HVAF system. We wholeheartedly agreed with this decision.

For more information on Metal Spray equipment or consumables, call us on 07 3823 1004, or email us using our contact form.

Metal Spray Equipment