Wear on parts that are in contact, sliding or under heavy load, can be drastically reduced by coating them with a layer of nickel which has been deposited without the use of electricity.
What Hardness the Coating Delivers
Typically, the hardness of Electroless Nickel Plating in the as-deposited condition is around 500 to 600 HV (Vickers Hardness) and, as a comparison, the hardness of mild steel is around 120 to 180 HV. This high hardness of the nickel coating in relation to the steel substrate means that the coating is inherently wearing much better than the part it has been coated with.
How Phosphorus Content Shapes Wear Behaviour
The phosphorus content of the nickel bath can be altered to either increase the hardness and wear resistance of the deposit or to increase corrosion resistance. Coatings that are produced from low-phosphorus baths (2 to 5%P) are the hardest as-plated and are recommended for the toughest abrasive wear applications. High-phosphorus deposits (10 to 12%P) are softer than low-phosphorus deposits but have excellent corrosion resistance and are recommended for applications where moderate wear resistance and excellent corrosion resistance are required.
Uniform Thickness on Complex Shapes
Unlike electroplated nickel coatings, Electroless Nickel coatings deposit at a constant thickness on all surfaces. This is particularly important on parts with small holes or threads, or other internal surfaces, such as bore holes, or valve bodies. On these types of parts, uneven thickness of plated coatings can result in some areas being much thicker than others. These areas of excess thickness would wear down faster than the thinner areas, resulting in early wear.
Heat Treatment Pushes Hardness Further
By heat treating the part to approximately 400°C for one hour, the nickel phosphorus coating can be increased in hardness to approximately 900-1100 HV, comparable to hard chrome. This information is useful when measuring hardness, and performing surface tests on components that have been electroless nickel plated.
Low Friction Under Load
2 against steel, thus reducing adhesive wear and galling in sliding contacts.
If you want Electroless Nickel Plating, www.poeton.co.uk/surface-treatments/plating/electroless-nickel-plating/ is a good place to start.
Pump shafts, valve stems, mould components, and other wear components such as those used in textile machinery can extend their service life due to the hardened, wear-resistant and low friction coating.
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