Functionally Graded Thermal Spray Coatings: Methods, Parameters, and Post-Spray Treatments

Surface coating on metal substrates has remained a difficult challenge for researchers due to the conflicting requirements for different properties. In recent years, due to their mechanical, thermal, electrical, and tribological properties in many advanced engineering applications, functionally graded coatings (FGCs) have become fascinating materials for researchers worldwide to obtain coatings with specific requirements. FGCs are a novel type of traditional composites in which phases are not equally distributed to form a smooth gradient structure; thus, gradient coatings have shown a new research path.The present paper tries to describe briefly major thermal spray techniques used to spray functionally graded coatings such as atmospheric plasma spraying, high velocity oxy-fuel spraying, suspension and solution precursor plasma spraying, and finally low and high-pressure cold gas spray methods. The examples of combined spray processes as well as some examples of post-spray treatment including laser and high temperature treatments or mechanical ones, are described.

Keywords:

FGCs , Thermal Spray Coatings , Process parameters , Post-Spray Treatment