The Properties of Nickel Deposit

The deposit properties of an electroless nickel layer, and subsequently the performance of the plated component depend upon the following:

-The phosphorous content

-The purity

-The substrate

-The pre-treatment

-The thickness

The structure of nickel phosphorous deposits is either micro crystalline or amorphous, which is a form of metallic glass. Nickel phosphorous deposits are homogenous and generally pore free.

Electroless nickel deposits possess excellent chemical resistance and corrosion protection properties. Electroless nickel deposits are resistant against most organic and inorganic chemicals apart from oxidising acids. The chemical resistance is especially good in neutral and alkaline solutions and a protective layer of electroless nickel on steel or aluminiuim can provide years of lasting protection against even aggressive industrial and marine conditions. The thickness of the deposit depends on the specific corrosive conditions and there are recommendations for each.

Mechanical properties of electroless nickel deposits

Electroless nickel deposits can be plated with tensile or compressive stress. Depending on the type of deposit, the ductility is between 0.1 and 2%. The micro hardness of electroless nickel deposit layers is between 500 to 700 Vickers Pyramid Number.

Electroless nickel layers can also be co-deposited with different inclusions for many applications. This is used particularly to give improved abrasion resistance. Electroless nickel can be co-deposited with silicon carbide, PTFE or even diamond.

Electroless nickel deposits may also be heat treated to temperatures above 240 degrees centigrade. This process can improve abrasion resistance and increase hardness. It can also enhance adhesion. To achieve maximum levels of hardness, parts are required to be treated at a temperature of 400 degrees centigrade for one hour. It is possible to enhance the abrasive wear resistance of electroless nickel deposits by using heat treatment in this way. The average coefficient of friction is about 0.3 and can be much smaller in certain cases, even as low as 0.03.

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