The current work investigates the effects of variation of coating bath temperature on friction and wear behaviour of electroless Ni–B (ENB) coatings developed from stabilizer free bath. Coating is applied to specimens made up of AISI 1040 steel. Coatings were deposited at three different coating bath temperatures (85°C, 90°C and 95°C). Field emission scanning electron microscopy, inductively coupled plasma-optical emission spectrometer, and X-ray diffraction were used to characterize the coating for surface morphology, chemical composition, and phase structure respectively. Pin-on-disc tribo-tester was used to estimate the friction and wear behaviour of ENB coatings at room temperature (25ºC), 100ºC, 200ºC and 300ºC. The coefficient of friction was higher at high temperature due to higher roughness of the coatings obtained from stabilizer free bath, adhesion and ploughing. The wear rate at 200°C or 300°C was lower compared to 100°C. Additionally, the ENB coatings were subjected to thermogravimetric analysis which reveals higher thermal stability of coatings obtained at 95°C. A scratch tester at constant (6 N) and progressive load (5-24 N) was used to estimate the coatings scratch hardness and adhesion. The corrosion behaviour of ENB coatings in 3.5 % NaCl was studied using potentiodynamic polarization tests. The Ni-B coated specimens could efficiently provide barrier protection to steel substrate. But the corrosion potential was lower compared to lead stabilized bath.

AISI 1040 steel offers a wide range of industrial applications due to its mechanical characteristics and applicability. The present work investigates the wear performance of AISI 1040 steel under dry sliding conditions and its optimization using combined machine learning (ML) and metaheuristic algorithm. Sliding wear test were carried out on a pin-on-disc tribometer by varying the load (10–100 N), sliding speed (0.5–1.5 m/s) and sliding distance (400–1000 m). The test parameters were varied at three levels. Experiments were carried out following combinations in Taguchi's L27 orthogonal array (OA). Artificial neural network (ANN) was used to model the process parameters with wear rate. The trained network was optimized using genetic algorithm (GA) to predict optimal wear rate. This methodology has been termed as ANN-GA method. The results were compared with conventional Taguchi based and regression based GA optimization. A significant reduction in the wear rate could be realized due to optimization using ANN-GA method. This work also examined the corrosion behaviour of AISI 1040 steel exposed to 3.5% NaCl, 3.5% NaOH, 0.5 M H2SO4 and 3.5% NaCl + 0.5 M H2SO4 to simulate various corrosive environments encountered in industrial applications. A nobler corrosion potential was obtained in 3.5% NaOH. Investigations of corroded samples showed pitting corrosion in 3.5% NaCl, 0.5 M H2SO4 as well as combined chloride and sulphate attack. On the other hand, negligible corrosion was observed in 3.5% NaOH.

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Electroless nickel boron coatings have wide industrial usage. However, they are generally obtained from a lead-stabilized bath. The present work investigates and optimizes the scratch-hardness and microhardness obtained from stabilizer-free electroless nickel boron bath in a quest to eliminate lead nitrate/heavy metals, which are potentially toxic. The bath temperature, heat treatment temperature, and duration were varied at three levels. Enhanced scratch-hardness (12.581GPa) was obtained at 85℃ bath temperature and heat treatment at 350℃ for 1 hour. At the same time, the highest microhardness (886.17 HV100) was obtained at a parametric combination of 95℃ bath temperature and heat treatment at 450℃ for 1 hour. Multi-objective optimization was carried out using grey relational analysis. The parametric combination predicted in multi-objective optimization was 85℃ bath temperature and heat treatment at 350℃ for 1 hour where the microhardness was 846.34 HV100. Furthermore, an analysis of variance was also carried out to investigate the importance of the factors in controlling scratch-hardness and microhardness. The highest contribution was observed from heat treatment duration. Further investigation of the optimized coating was done by the progressive scratch test, which recorded that the first critical load of failure improved compared to non-heat treated electroless Ni-B coatings. The coatings were also characterized using field emission scanning electron microscope, energy dispersive x-ray spectroscopy, and x-ray diffraction. The coatings in optimized condition showed no transverse or chevron cracks within 5-24 N.