A variety of metallic powder particles were thermally sprayedonto the mirror polished metallic substrate surface and theeffect of both substrate temperature and ambient pressure onthe flattening behavior of the particle was systematicallyinvestigated. In the flattening behavior of the sprayed particleonto the substrate surface, critical conditions were recognizedboth in the substrate temperature and ambient pressure. That is,the flattening behavior changed transitionally on that criticaltemperature and pressure range, respectively. A transitiontemperature, Tt, and transition pressure, Pt, were defined andintroduced, respectively for those critical conditions. The factthat the dependence both of transition temperature andtransition pressure on the sprayed particle material had similartendency indicated that the wetting of the substrate by themolten particles seemed to be domination in the flattening.Three dimensional transition curvature by combining bothtransition temperature and transition pressure dependence wasproposed as a practical and effective controlling principle ofthe thermal spray process.
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