The microstructural changes of electroless Ni–P–Cu coating at various heat-treatment conditions are investigated to understand its implications on the tribological behavior of the coating. Coatings are heat-treated at temperatures ranging between 200°C and 800 °C and for 1–4 h duration. Ni–P–Cu coatings exhibit two-phase transformations in the temperature range of 350–450 °C and the resulting microstructural changes are found to significantly affect their thermal stability and tribological attributes. Hardness of the coating doubles when heat-treated at 452 °C, due to the formation of harder Ni₃P phase and crystalline NiCu. Better friction and wear performance are also noted upon heat treatment of the coating at the phase transformation regime, particularly at 400 °C. Wear mechanism is characterized by a mixed adhesive cum abrasive wear phenomena. Heat treatment at higher temperature (600 °C and above) and longer duration (4 h) results in grain coarsening phenomenon, which negatively influences the hardness and tribological characteristics of the coating. Besides, diffusion of iron from the ferrous substrate as well as greater oxide formation are noticed when the coating is heat-treated at higher temperatures and for longer durations (4 h).

研究了化学热处理的Ni–P–Cu涂层在各种热处理条件下的微观结构变化，以了解其对涂层的摩擦学行为的影响。涂层要在200°C至800°C的温度范围内进行1-4小时的热处理。Ni–P–Cu涂层在350–450°C的温度范围内表现出两相转变，并且所发现的微观结构变化会显着影响其热稳定性和摩擦学特性。在452°C热处理时，涂层的硬度增加了一倍，这是由于形成了较硬的Ni ₃P相和结晶NiCu。在相变状态下，特别是在400°C下对涂层进行热处理时，也注意到了更好的摩擦和磨损性能。磨损机理的特征在于混合的粘合剂兼有磨料磨损现象。在较高温度（600°C及以上）和较长时间（4小时）下进行热处理会导致晶粒粗化现象，这会对涂层的硬度和摩擦学特性产生负面影响。此外，当在较高的温度和更长的持续时间（4小时）内对涂层进行热处理时，会注意到铁从铁质基材中的扩散以及更大的氧化物形成。