Abstract:

A piece of electroless Ni-W-P composite coating was prepared on copper substrates. X-ray diffraction results show the coating has an amorphous structure. The results of adhesion test and pool boiling experiment all indicate that the scale adhesion speed on the electroless Ni-W-P coating with lower surface free energy is reduced by 52%，the average value of heat transfer coefficient is 1.7 times that of plain copper surface when boiling in calcium sulphate solution. The bubble behavior on boiling surface was captured by a high speed camera. Depending on the heat transfer mechanism，two different types of deposits have been observed. A needle-like structure is the characteristic of scale formed on a plain copper surface，while a granular structure corresponds to the scale formed on the Ni–W–P coating surface.