Friction and Wear Characteristics of Heat Treated Electroless Ni–P–W Coatings Under Elevated Temperature

Abstract

Tribological characteristics of Ni–P–W coatings at elevated temperature developed via autocatalytic deposition over mild steel have been researched. The film is portrayed for its crystallographic arrangement, morphology, solidity and the tribological attributes. A pin-on-disc set-up in which EN 31 plate is used as static counterpart is employed. All the wear experiments are done under room condition and also to 500 °C. The deposited Ni–P–W covered surface has a blend of amorphous and crystalline phase, and it ends up fully crystalline with the formation of Ni–W and Ni3P after heating operation at 400 °C for 1 h. EDX investigation reveals the content of tungsten in the Ni–P–W combination to be around 4.5 wt%. Wear resistance of coating is observed to be negatively affected by the test temperature. Wear rate is inversely related with sliding velocity for a fixed value of load in high-temperature tests. Coefficient of friction, however, remained almost passive to elevated temperature tests. Wear rate is also found to vary with the applied load for a fixed sliding velocity. Increase in temperature causes increase in wear rate because of material softening at elevated temperature. Abrasive wear mechanism is observed for the Ni–P–W film examined at room condition, while for the same tested at a temperature of 500 °C, a mix adhesive and abrasive wear system are noted.