Cavitation erosion behavior of electroless nickel-plating on AISI 1045 steel

Electroless nickel-plating is widely used in anti-corrosion engineering with a bonus of the capability of precipitation hardening due to Ni3P formation after a 1 h heat treatment at 400 °C. But its application in cavitation erosion protection has been rarely discussed in the literature. In this study, electroless nickel-plating is produced on AISI 1045 steel with and without post-heat treatment and cavitation erosion test is evaluated. The test was carried out both in distilled water and 3.5 wt.% NaCl solution, respectively. The results showed that the specimen having an electroless nickel film, without post-heat treatment, underwent an easy flaking-off during both cavitation erosion tests, whereby the cumulative mass loss of the specimens was much higher than the mass loss of the blank steel substrate or the electroless nickel-plating with post-heat treatment (PHT) due to weak adhesion strength of film. Specimens, which had undergone post-heat treatment showed a dramatic reduction in cumulative mass loss in both distilled water and 3.5% NaCl solution. The damage developed on the surface of the specimen suggests that the progress of material removal via fatigue was caused by the brittle nature of the PHT nickel-plating layer. From an electrochemical point of view, the PHT specimen resembled the as-plated specimen in 3.5 wt.% NaCl solution, indicating that the cavitation resistance of the PHT specimen originated from enhanced mechanical strength due to precipitation hardening. However, when the plated nickel film is eroded, a galvanic corrosion will start between the plated film and the steel substrate damaging the steel substrate, especially in cavitation erosion systems.