THE EFFECT OF BATH TEMPERATURE ON THE STRUCTURE AND TRIBOLOGICAL BEHAVIOR OF ELECTROLESS Ni-B-Mo COATINGS OBTAINED FROM STABILIZER-FREE BATH

Conventional electroless Ni-B-Mo (ENB-Mo) deposits are formed using hazardous lead or thallium-containing solutions, which must be removed. In this study, ENB-Mo deposits were developed in a bath free of stabilizers and harmful heavy metals. This study estimates the effect of variation of coating bath temperature on tribological performance of ENB-Mo coating developed over AISI 1040 steel. The chosen bath temperatures were 85(degrees)C, 90(degrees)C, and 95(degrees)C to achieve ENB-Mo coating with varying B and Mo content. The 12-15 mu m thick coating was uniform. In comparison to steel substrate, all of the coatings show enhanced corrosion resistance. In the as-deposited state, coatings were mixed amorphous and nanocrystalline with peak of Fe overlapping with Ni. Moreover, TGA results revealed that inclusion of molybdenum enhanced coatings thermal stability. The worn specimens at 300(degrees)C reveal development of shielding tribo-oxide coatings and existence of microstructural changes. At high working temperatures (300(degrees)C), wear debris also has a major impact on tribological mechanisms of coatings. Correlation between microstructure, tribological behavior, and corrosion resistance have also been conducted for ENB-Mo coatings.