Hard electroless nickel plating is an electroless nickel coating (9–12 wt% P) that is heat treated at 273 °C.
To crystallise its originally amorphous structure. Longer times and higher temperatures lead to higher hardnesses.
With a hardness rating of 950 Vickers viewed as the gold standard. In some cases, hard electroless nickel plating may be an alternative to hard chrome.
The high P content (> 9 wt%) gives the electroless nickel coating excellent resistance to corrosion. Different results can be achieved, depending on the thickness of the coating.
Heat treatment does have a negative affect on corrosion resistance.
Corrosion resistance in accordance with the neutral salt spray test under ISO 9227
Hardness of 950 HV as a result of heat treatment (273 °C, 12 h).
This type of coating is used in applications requiring high wear resistance.
Important! The heat treatment used to harden the coating may impact:
Deformations
Stresses in welded constructions
Mechanical properties
The tempering temperature of hardened steel
Low-phosphorus electroless nickel plating (1–3 wt% P) may be an alternative, with a hardness of >750 HV as deposited (no heat treatment).
