Properties of Electroless Nickel - Phosphorus PPF Deposits after Crystallization

t is well recognized that electroless I.' nickel-phosphorus offers excellent deposition characteristics, such as uniform coverage, freedom from porosity, hardness, corrosion resistance, solderability, braze and weldability, wear resistance and lubricity.' Interest in the properties of electroless nickel has grown in recent years, leading to the development of wide-ranging applications, a comprehensive list of which was provided by Ehmardt.2 The influence of electroless nickel-phosphorus deposits on the corrosion and wear resistance and fatigue behavior of mild steels is now well demon~trated.3~~ The as-plated nickel-phosphorus deposit is a compact metallic body possessing an amorphous structure. The amorphous nature of the deposit is substantiated by X-ray diffraction (XRD), electron diffraction and highresolution microscopy? A phase diagram study of the nickel-phosphorus system showed the presence of three intermetallic compounds (Ni,P, Ni,P, and Ni,P) in addition to the solid phase of phosphorus in nickel.? An account of the crystallization of nickel-phosphorus deposits was presented by Lin and Lai? mainly on the basis of XRD data at temperatures of 200, 300, 500 and 800°C. This article reports the quantitative development of crystallinity in nickel-phosphorus deposits in the range 300400°C and clarifies the process of crystallization. Variation in hardness, wear, erosion and resistivity characteristics of electroless nickelphosphorus deposits subjected to different heat-treatment temperatures is also covered in this study.