Elastic modulus measurements in plasma sprayed deposits

A commercial hardness indenter has been modified to record load displacemen t as a spherical ball is elastically loaded onto the surface of the materia l to be measured. The resulting data are used to calculate the elastic modu lus. This technique has been used to characterize the elastic modulus of zi rconium oxide-8% yttrium oxide plasma sprayed deposits. Moduli were measure d both on the cross section and on the plan section, and the differences we re correlated with the microstructure. Since relatively small areas of the material were sampled by the indenter, local mapping of elastic modulus var iations on the size scale of the microstructure was possible. A periodic va riation in modulus with position in the cross section was found on a length scale that corresponded to the average plasma spray pass thickness, Elasti c modulus variations also have been found on a macro scale through the thic kness of freestanding plasma sprayed deposits. These large scale variations were probably a result of self annealing during the production of these th ick samples. Finally, significant increases in elastic modulus have been fo und in samples annealed for a total of 2.5 h at 1100 degrees C. These chang es have been correlated with small angle neutron scattering measurements of void surface area.