Precision Cleaning Titanium Components

Clean bond surfaces are critical to the operation of diffusion bonded titanium engine components. These components can be contaminated with machining coolant, shop dirt, and fingerprints during normal processing and handling. These contaminants must be removed to achieve acceptable bond quality. As environmental concerns become more important in manufacturing, elimination of the use of hazardous materials is desired. For this reason, another process (not using nitric-hydrofluoric acid solution) to clean titanium parts before bonding was sought. Initial cleaning trials were conducted at Honeywell to screen potential cleaning techniques and chemistries. During the initial cleaning process screening phase, Pratt and Whitney provided Honeywell with machined 3 inch x 3 inch x 1 inch titanium test blocks. These test blocks were machined with a water-based machining coolant and exposed to a normal shop environment and handling. (Honeywell sectioned one of these blocks into smaller samples to be used for additional cleanliness verification analyses.) The sample test blocks were ultrasonically cleaned in alkaline solutions and AUGER analysis was used by Honeywell FM and T to validate their cleanliness. This information enabled selection of final cleaning techniques and solutions to be used for the bonding trials. To validate Honeywell's AUGER data and to verify the cleaning processes in actual situations, additional sample blocks were cleaned (using the chosen processes) and then bonded. The bond quality of the test blocks was analyzed according to Pratt and Whitney's requirements. The Charpy impact testing was performed according to ASTM procedure {number_sign}E-23. Bond quality was determined by examining metallographic samples of the bonded test blocks for porosity along the bondline