Digital deposition of yttria patterns on titanium sheets

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (leaf 77).The ability to apply Yttria patterns on titanium sheets is required on a secondary manufacturing operation. The freedom to create 2 dimensional patterns as well as 3 dimensional ones by using Three Dimensional Printing allows for the application of Yttria patterns onto these sheets without the use of any type of screens. Two methods for creating these patterns were identified and studied. The first approach consists of selectively printing binder on top of spread layer of powder. A second layer of powder is spread while the binder is still wet. The binder will then dry fixing the Yttria powder to the sheet on the selected positions. Sheets were printed using different particle sizes. Results show that patterns can be applied with good edge definition and uniform thickness using powder ranging from -53[mu]m down to -20[mu]m. The sheets were tested successfully in the secondary operation. And alternative approach consists of mixing the binder and the ceramic powder to create a slurry. The slurry will then be selectively printed onto the sheet using Three Dimensional Printing. A formulation for a -20 [mu]m Yttria powder slurry was developed using Poly Acrylic Acid as dispersant and Polyethylene Glycol as binder. Slurries with 20 volume fraction and less were dispersed and jetted through a 102 [mu]m nozzle. These slurries adhered well to the titanium sheet as they were printed. The formulation was tested successfully in the secondary operation. Following the High-Risk Approach patterns without deflection were printed. For a 102 [mu]m nozzle the best flow rate was determined, as well as the optimal line spacing. The best procedure to print a certain area was to print a first round of lines, dry them and then print lines in between the first set. The average roughness of the layer printed was 14 [mu]m. In order to allow future printing of slurries with a nozzle size of 102 [mu]m and deflection, the design of a print head to accommodate these slurries was also investigated.by Gabriel Fernandez.S.M