Stability of electrodeposited amorphous Ni-Fe-P alloys

The stability of the electrodeposited amorphous Ni-Fe-P alloys was studied by DTA, DSC, XRD and improved four-ball wear tester in order to clear its applied scope. The results show that the element content has influence on the stability of amorphous Ni-Fe-P alloy, in which the crystallization temperature increases with Fe content, and the increase of P content delays the appearance of stable crystallization phases and recrystallization. There exist 6 exothermal reactions during heating the amorphous Ni69Fe8P23 alloy continuously. The activation energies of exothermal reactions at 248, 303, 322, 350, 376 and 442 °C are 131.5, 111.6, 237.8, 253.6 and 238.5 kJ/mol, respectively. The amorphous Ni60Fe22P18 alloy crystallizes when the heating temperature is beyond 250 °C. The stable crystallization phases consist of Ni (Fe) and Ni3P-type compounds Ni3P, Fe3P, (Fe,Ni)3P. The pressure and fraction have influence on the stability of amorphous alloy. Rubbing above the critical pressure crystallization will take place on the fractional surface. The crystallization phases due to pressure and fraction are different from those due to heating. It is the crystallization that increases the wear resistance of Ni-Fe-P coating under higher pressure.