Heat Treatments

After deposition, NIPLATE® coatings can undergo post-plating heat treatments, carried out depending on the base material, the required performance, and the component’s technical specifications.
The most commonly applied heat treatments are dehydrogenation and coating hardening.

These treatments should not be considered standard optional steps, but rather technical operations to be assessed consciously, as they affect both the properties of the electroless nickel coating and, in some cases, the mechanical characteristics of the base material.

Dehydrogenation

During pre-treatment and electroless nickel plating, atomic hydrogen can diffuse into the metallic matrix of both the coating and the substrate. If not controlled, this phenomenon can lead to a deterioration of the material’s mechanical properties, known as hydrogen embrittlement.

Hydrogen embrittlement is a particularly relevant risk for:

• high-strength steels,
• titanium alloys,
• materials that are sensitive to the presence of hydrogen diffused within the crystal structure.

In the electroless nickel plating process, the absence of electrical current results in a significantly lower hydrogen introduction than traditional electrolytic coatings, such as chromium plating or electrolytic nickel plating. However, when critical materials are involved or particularly stringent specifications apply, dehydrogenation remains a recommended preventive measure.

In particular, dehydrogenation is recommended for steels with tensile strength greater than 1000 MPa, or for quenched or case-hardened steels.

Dehydrogenation consists of a low-temperature heat treatment, typically carried out at 150–180 °C for approximately 4 hours, intended to promote diffusion and release of residual hydrogen from the coating–substrate system.

Coating hardening

Electroless nickel plating NIPLATE® coatings can undergo a hardening heat treatment to increase hardness and wear resistance.

Hardening occurs through a structural transformation of the nickel–phosphorus alloy: the heat treatment induces the formation of Ni₃P precipitates within the coating matrix. These aggregates significantly increase surface hardness and improve the coating’s tribological behavior.

Depending on the treatment temperature and time, the deposit hardness can increase:

• from typical initial values of 500–600 HV,
• up to values on the order of 1000–1100 HV.

The most commonly used hardening cycles are:

• 260–280 °C for 8 hours, or
• 330–350 °C for 4 hours,

with progressive improvements in the coating’s mechanical performance as the treatment temperature increases.

It is important to consider that the hardening treatment primarily affects the coating, but it can also influence the base material, especially in the case of alloys that are sensitive to thermal cycles.