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  Coating Selection for Contact with an Engineering Component in the Presence of an Abrasive and Corrosive Product or Environment  

 
If a component contains surfaces which roll or slide against each other with abrasive and/or corrosive product trapped between them, then it creates a very extreme situation of three-body high stress abrasive wear.

Before continuing with the analysis, you should read the section on high stress abrasion.

It is particularly common in pumps, valves and mechanical seals which are working with abrasive slurries such as sand, water and hydrocarbons as found in oil and gas extraction. The situation is typified by a crushing and grinding action between the surfaces (perhaps the two sliding surfaces of a journal bearing) which breaks down the abrasive particles and continuously creates new cutting edges. When combined with corrosion this creates a very extreme wear situation.

The base material

The substrate is most likely to be austenitic or ferritic stainless steel, high alloy hardenable steels, nickel-based alloys (e.g. Inconels) or even cast grades of nickel/cobalt/chrome/carbide-based materials of the Stellite variety.

Surface Engineering Options

These are limited to those which provide combined hardness, toughness, load-carrying capacity and corrosion resistance:

  1. Welded or Spray-Fused Coatings. Nickel or cobalt-based materials with high carbide content, deposited to at least 2mm thick
  2. Thermally Sprayed and HIPPED Coatings, Nickel and iron-based materials with high carbide content (Tungsten and Chrome), deposited to at thicknesses of 5mm or more
  3. High-Velocity Thermally Sprayed Coatings, Nickel or cobalt-based cermets with low porosity and high bond integrity, at least 1mm thick
  4. Chomising for combined corrosion and wear resistance
  5. Boronising for high wear resistance of alloy steels, but without good corrosion resistance. Cast Stellites can be Boronised
  6. Hard Chrome Plate if the substrate is corrosion resistant and the situation is not too aggressive. Crevice corrosion can undermine the plating
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