This chapter reviews various process and parameters optimization techniques. Further, focusing on the latest coating materials, including ceramics, metals, and composites, with a focus on their improved performance, the research also examines cutting-edge coating quality diagnostics and characterization methods. Finally, the different applications of coatings in various sectors, such as wear resistance, thermal insulation, mechanical strength and corrosion protection etc. are explored and highlighted their critical roles in industries like aerospace, automotive, energy and constructions.