SHS POWDERS FOR THERMAL SPRAY APPLICATIONS

Self-propagating high temperature synthesis (SHS) is defined as a comb ustion process in which reagents, when ignited, spontaneously transfor m, to complete conversion, into products, due to the exothermic heat o f reaction. This process has been recently recognised as a very promis ing technique for materials processing: ceramics, intermetallics and c ermets with good physico-chemical properties have been produced at low costs. The use of SHS products for thermal spray applications represe nts a natural evolution of the technique. Demanded characteristics for thermal spray feedstock powders can be very different, depending on t he spraying process, the operating conditions, the desired properties of the final coating, etc. However, technical requirements can also be extremely rigid and detailed. As a consequence, the production proces s must be reliable and flexible, while remaining possibly inexpensive. SHS is investigated as a promising candidate technique for the produc tion of different powders to be used for thermal spray coatings with d ifferent applications: metallic mixtures are considered, as well as ce ramic and composite powders. The chemical and morphological features o f different SHS powders are described, and their technical characteris tics of flowability and sprayability are outlined. Wear performance an d hardness tests results for some of the coatings obtained by both air and vacuum plasma spraying of SHS powders are also reported. (C) 1996 Elsevier Science Limited and Techna S.r.l.