Abstract: A substrate is coated by applying an essentially pure aluminum first layer to a surface of the substrate. At least a first portion of the first layer is oxidized so as to provide a protective coating of desired properties. The substrate may be a refractory metal-based investment casting core.

Abstract: To destructively remove a refractory metal casting core from a cast part the part is exposed to a combination of nitric acid and sulfuric acid.

Abstract: A method for forming an investment casting core comprises cutting a patterned core precursor from refractory metal-based sheet. The cutting forms recast along the cuts. An oxide is grown on non-recast areas. The recast is substantially chemically removed but substantially leaving the oxide. The core precursor may then be shaped.

Abstract: To destructively remove a refractory metal casting core from a cast part the part is exposed to a combination of nitric acid and sulfuric acid.

Abstract: A substrate is coated by applying an essentially pure aluminum first layer to a surface of the substrate. At least a first portion of the first layer is oxidized so as to provide a protective coating of desired properties. The substrate may be a refractory metal-based investment casting core.

Abstract: A method of repairing a braze joint and the resulting joint includes removing an unsuitable portion of a first joining material in a joint between a first member and a second member of an aerospace assembly and cleaning the joint. A stripping solution is used to remove the unsuitable portion of the first joining material. A first cleaning solution is used to clean the joint, and the joint is further cleaned using a second cleaning solution. During a rebrazing step, a second joining material moves into a void left by the removed unsuitable portion from the removal step to form a new joint between the first member and the second member that includes the remaining first joining material and the second joining material.

Abstract: A substrate is coated by applying an essentially pure aluminum first layer to a surface of the substrate. At least a first portion of the first layer is oxidized so as to provide a protective coating of desired properties. The substrate may be a refractory metal-based investment casting core.