Surface Restore / Repair by Thermal Spray Coating
In most cases it is faster, cheaper and sufficient to rework the worn-out part to its original dimensions and thereby to re-establish the required properties of the part surface.
Undersized Shafts and Journals
When a shaft is worn below the design diameter of the part even by a few tenths of a millimetre, it can cause excessive play in bearings or even allow the part to be out of balance. This can cause excessive vibration and result in early part failure. As a result, the part can be surface restored to the original dimensions with Thermal Spray Coating. After the coating has been applied the part is then finished ground to the required tolerance.
Surface Pitting and Corrosion Damage
Pitting creates a weak area that can quickly start to wear even further. However, a sprayed coating can fill the pitted area to create a perfectly uniform surface, providing the parent metal is sound. However, sections that have corroded to the point where they have lost load bearing thickness are likely to be too far gone to be repaired by spray.
Worn Bearing Seats and Bores
Bearing seats are another common area for wear and damage. Fretting, increased clearance and corrosion are all common problems and can be repaired by spraying the bore and then re-machining to size. It is worth establishing the current geometry of the bore prior to commencing repair to determine if it is within recoverable limits or if other methods of repair are required.
Keyways and Localised Impact Damage
A spray repair can be very useful for restoring worn keyways and also for repairing local damage, such as dents, etc. caused by accidents etc. on otherwise sound components.
Abraded Wear Surfaces
Surface coatings can restore worn surfaces to their original hard wear surface, with process parameters for the spray being chosen to meet the required hardness and bond of the wear application. Typically work would be carried out to recognised material and surface engineering standards to ensure that the repair is a good one and performs as required.
In fact a simple check to see if a part can be repaired by thermal spray coating is to check if the base metal is sound and the amount of wear is within sprayable limits.
