Effect of brown rice husk α-Si 3 N 4 on Ni–P composite coating of austenitic AISI 316L steel: Taguchi grey relational approach

The aim of this present study was to investigate and optimize the effect of adding brown rice husk ash (BRHA)–derived α-silicon nitride (Si 3 N 4 ) and nickel-phosphorus (Ni–P) reinforcements onto the surface of austenitic AISI 316L bioimplantable stainless steel via electroless coating. This study brings the rationale about how the agricultural biomass-turned biomaterials serve as functional materials for recent advance engineering applications. α-Si 3 N 4 was prepared via a carbothermal reduction and nitriding process from brown rice husk ash. Using the Taguchi L9 orthogonal array experimental setup and the grey relational approach, the α-Si 3 N 4 /Ni–P-toughened austenitic stainless steel composite coatings were prepared and optimized. According to the optimization results, the coating temperature was found to be the most controlling process parameter among other variables such as reinforcement ratio and immersion time. Similarly, the process variables such as immersion time of 500 min, coating temperature of 90 °C, and reinforcement ratio of 0.9 (A 3 B 3 C 3 ) were found to be the new optimum process variables. Atomic force microscope (AFM) micrographs of coated surfaces confirm the uniform deposition of α-Si 3 N 4 , Ni and P at 70 and 90 °C. The additions of Si 3 N 4 neatly reinforce into the crystal lattice of iron and offered high hardness and wear resistance than Ni–P. The grey relational grade value was improved from 0.879 to 0.896 for optimized process variables. The tensile strength of 911.12 MPa, surface hardness of 197.45 BHN, and specific wear rate of 0.00000491 mm 3 /Nm were observed from the optimized study, which was about 1.94% of improvement in comparison with the Taguchi model.