Mainly used for corrosion protection and to create a low friction surface. The electroless method of application ensures completely even deposits and no edge build-up. Typical coating thickness of 8-12 microns is standard, but precise coating thicknesses can be specified. The mid-high phosphorous content on our E-Nickel provides the ability to age-harden the layer from an as-plated hardness of ± 450 Hv to ± 950 Hv ( 45 HRc → 69 HRc). The aging treatment, while improving the layer wear resistance, also enhances adhesion.
The higher phosphurous E-Nickel coatings have the advantage of:
- Low friction (vs steel: 0.38- dry, 0,21 – lubricated)
- Lower porosity (i.e. improved corrosion resistance)
- Low thermal expansion
Composite E-N Coatings
Electroless nickel can also be plated togther with other fine particulates such as Teflon, Silicon Carbide, Boron Nitride and Diamond, to give a composite coating. Each type of particle gives the normal E-Nickel layer enhanced performance properties not normally found. Our Metal Teflon Coating (MTC) coating is essentially an E-N coating with a composite top coat that contains up to 25% Teflon/PTFE particles in the layer. This enhances the release and flow ability of the surface and it is particularty important for the plastics industry where it is assists in plastic release and flow for complicated mould designs incorporating ribs and recesses. Plastic moulders have reported reduction in cycle time of between 4-8% using MTC. It is also used very succesfully on parts requiring a durable, dry running, low friction surface such as feeders, slides and shafts. MTC further has the advantage of a constant friction coefficient under a wide range of loads. Due to the electroless nature of the coating, internals and difficult geometries are easily coatable.
Up to 25% of the coating is made up of sub-micron sized PTFE (Poly-Tetra-Fluorine-Ethylene) or Teflon. This is held in a Nickel phosphorous layer typically 10-15 microns in thickness. MTC applies evenly at 90 °C and can be applied to aluminium, steel and copper without fear of distortion or thermal change to the base material. A uniform plating thickness develops wherever the solution contacts the part. Groves, slots, threads and even the inside of tubing can have uniform thickness of coating.
Should a temperature resistance of more than 300°C be required, the Teflon can be replaced with Boron Nitride. The E-N/BN coatings have successfully been used to enhance release properties in complex moulds and offer moderate wear resistance, excellent lubricity and release properties which outperforms most other coatings.
Nikisil is an Electroless Nickel layer with a Silicon Carbide infused top layer. As the SiC is a very hard substance, it significantly improves wear resistance and it is an effective competitor to chrome plating, but without the limitiation of chrome plating with regards to edge built up and limited throwing power. Nikisil is able to follow virtually all contours and internal holes and passages making it a very effective coating for complex shapes.
ref:Electroless Nickel Composite Coatings, Advanced Materials & Processes, May 2008