Microstructure, deformation and cracking characteristics of thermal spray ferrous coatings

The microstructure and local mechanical characteristics of thermal spray fe rrous coatings have been determined. The emphasis has been on coatings made by the high velocity oxyfuel (HVOF) process, especially the role of Al all oy additives. The oxide phase present in the material and preferred pathway s for local cracking and separation have been determined. Thin intersplat o xide layers emerge as preferential sites. These oxides are amorphous and th e cracks extend along the oxide/alpha-Fe interfaces with low local fracture toughness, in the range 0.2-1 MPa root m. These low toughness pathways gov ern coating deterioration. (C) 1999 Elsevier Science S.A. All rights reserv ed.