Novel Strategy for Developing Bulk-Like Dense Metallic Coatings by Plasma Spraying

Although thermal spray metallic coatings have been widely used for materials protection from wear, corrosion and oxidation, its porous feature limits the full utilization of materials potential. Moreover, the oxidation inherent to thermal spraying in ambient atmosphere is detrimental to interlamellar bonding formation, which further reduces coating performance. Facing such challenge, the novel strategies to deposit oxide-free dense metallic coatings with sufficiently bonded lamellae by plasma spraying has been developing. The strategy includes development of the ultrahigh temperature metallic droplets up to 2650^oC with the insitu deoxide effect achieved by material design with deoxiding element in the powder. The evaporation or gasification of the resultant oxides at high temperature generates the in-situ deoxiding effect during in-flight. Moreover, the subsequent impact of ultra-high temperature droplets creates a spreading-fusing self-metallurgical bonding effect. Thus, fully dense bulk-like metallic coatings can be formed by APS. The typical examples of NiCrMo and 304SS-Mo coatings, NiCrBSi coatings, Al coating are presented to show clearly the possibility to deposit metal coatings with sufficiently bonded lamellae by plasma spraying. Such strategy will tape out the full potential of coating materials and open up the new application fields for plasma spraying.