What Can Thermal Spray Coating Repair on Worn Metal Parts?
Worn parts don’t have to get thrown away. The type of wear that a part has suffered will dictate whether or not it can be repaired with a spray coating.
Undersized Journal Diameters
As wear occurs the journal surface diameter can decrease below the original designed tolerance. These parts are normally scrapped or sent for repair. By using the correct spray coating material (tungsten carbide or nickel based alloys) to build up the diameter of the shaft journal, the part can then be surfaced to the required size as per the original design drawings. This spray coating adheres well to steel and gives good wear resistance under high loads whilst in rotation.
Pitted or Scored Bearing Housings
Pitted or scored on the inside of Bearing Housings can be repaired with a spray coating. The coating fills in the pits and provides a smooth surface, which can then be bored or honed to size to provide a precise fit. The part can then be returned to service.
Eroded Pump and Valve Components
Spray coating can also be used to reface worn surfaces of pump casings, impellers and valve bodies. These components are subject to wear due to erosion caused by abrasive slurries. As noted in Government process guidance on thermal spraying, HVOF-applied coatings achieve very low porosity, thus the face of the wear re-faced part is likely to offer improved erosion resistance than the original part.
Corroded or Pitted Shaft Surfaces
General corrosion or local surface damage, including pitting and crevicing, can occur on in-service stored shafts and other metal parts in damp or chemically active environments. A corrosion resistant coating layer such as stainless or nickel spray can provide a completely sealed surface which can be machined if required and used immediately.
Spray coating may be worth investigating before purchasing a replacement part if wear, erosion or corrosion has caused the part to lose material.
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