Engineered Surfaces for Exceptional Performance
Engineered Surfaces for Exceptional Performance

Reducing waste while saving time and money is a sought-after requirement and is a necessity for modern industries. Metal/Thermal Spray processes provide the means to achieve these goals as they provide a fast turnaround when performing repairs on parts that have been out of tolerance during service, but are otherwise in good order. Repairs are much more cost-effective than purchasing new replacement parts.

Components may become out of tolerance due to:

  • Abrasive, corrosive, or adhesive wear.
  • Physical abuse (bent journals, scratches, dents etc.).
  • Process defects (surface blemishes or casting imperfections).
  • Machining or processing errors.

The Metal Spray process involves the deposition of metal/ceramics onto a surface. The spray deposit is a series of micro-sized, semi-molten particles of material being applied in a stream of high-pressure gas or arc. Upon impacting the surface, these particles form a splat, quench, freeze and bond (to both the component and each other) to form a thin 0.003” to 0.005” (75 to 125 u) layer of new material.

Additional passes continue to provide material until the desired thickness is reached. This is usually an amount needed to restore dimensional size, plus a finishing allowance. The spray deposit may then be ground, machined, milled, filed, honed and emery polished to obtain the tight dimensional tolerances and surface profile that today’s operating equipment demands.

There is no need for extensive, time-consuming masking of the areas adjacent to a planned build-up area. Nor is there a need for extensive pre-machining that may further weaken a part.

In most cases the Metal Spray process does not require pre or post heat treatments or harsh chemical cleaning and the process itself can be portable.

Journal for Pinion Gear Reclaimed with Arc Spray

Metal Spraying can be used for:

  • Returning bent journals on all types and size shafting, rollers, and cylinders to in-line operating condition.
  • Salvaging mis-machined component diameters (either inner or outer).
  • Restoring scored/worn seal, bearing and gear diameters to optimal operating condition.
  • Re-establishing slide, tap or press fit dimensions and concentricity.
  • Reducing the need for and reliance on expensive replacement parts.
  • Increasing and improving the performance on running or sliding surfaces.

When compared to welding, Metal Spray is an economical and efficient ‘cold’ build up process. Relatively thick (>4mm) or thin deposits of many materials such as stainless steel, molybdenum, aluminium, aluminium bronze, tungsten carbide, and ceramics can be quickly and easily applied to Ferrous and Non-Ferrous surfaces without causing any warping or distortion, adversely affecting adjacent areas, changing mechanical properties or metallurgical characteristics.

Though the main feature of the Metal Spray process is its ability to return specified dimensions, an additional benefit is the ability to enhance performance by applying a more desirable, better performing material onto an out of tolerance surface. Applying to new components also gives added benefits. This is why cars are lighter in weight, more energy efficient, yet withstand their harsh operating environments.

Front Strut of Caterpillar Mining Truck being Reclaimed with HVOF

Almost any surface can be sprayed, from outside/inside diameters, to flat, convex or concave surfaces, up to edges, holes, flanges, radii and shoulders, all without the deposited material lifting, peeling, flaking, cracking, tapering or pulling away from the surface.

The Metal Spray process has been used since the early 1900’s and serves numerous industries, including, but not limited to Aerospace, Automotive/Transport, Engineering, Powder Coating, Reclamation and Hard-Facing. These industries, amongst others rely on the Metal/Thermal Spray process to save both time and money.

This article was previously published in a 2018 publication of Materials Australia - Industry News on behalf of MSSA.

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