STRUCTURAL-CHANGES INDUCED BY HEATING IN ELECTROLESS NICKEL PHOSPHORUS ALLOYS

Structural changes induced by heating were studied in electroless nickel-phosphorus alloy coatings at three phosphorus compositions: 1%-3%, 6.5%-8% and 10.5%-11% (by weight). X-ray diffraction patterns and pole figures for the (111) and (200) diffraction lines were obtained for as-plated coatings and coatings heated to temperatures from 235°C to 800°C. Microhardness tests were run on each coating. The low phosphorus composition (1%-3% P) as deposited was crystalline. It was single-phase nickel with an indication of a weak (100) texture. The strength of this texture increased with temperatures up to about 535°C. The Ni3P phase was detected at 425°C. The intermediate composition (6.5%-8% P) as deposited exhibited the diffraction pattern of an amorphous material. The fcc nickel structure with preferred orientation appeared after heating above 350°C. The texture was (110) and increase in strength with temperature to 800°C. A weak secondary texture, (100), was detected at higher temperatures. Ni3P was detected above 400°C. The high phosphorus alloy (10.5%-11% P) as deposited appeared amorphous. After heating to 385°C both nickel and Ni3P diffraction patterns were observed, but there was no confirmed preferred orientation in nickel. A duplex texture, consisting of (110) and (111), was found after heating to 425°C.