Edge-sealed fixture for processing CMC

A method for processing a ceramic matrix composite article, the method comprising:

• providing a fixture that includes first and second tool segments that each have an exterior side and an interior side, the interior side has a border mate face, the interior side of the first tool segment faces the interior side of the second tool segment such that the border mate faces align and circumscribe a working region, the first and second tool segments each having an array of through-holes that open to the working region, the first and second tool segments each including a support surface facing the working region and through which the through-holes extend, and the border mate face of the second tool segment is recessed from the support surface of the second tool segment such that the support surface of the second tool segment is on a plateau;
• situating a fiber preform in the working region;
• providing a seal that circumscribes the working region, the seal is united with the first tool segment;
• and
• exposing the fixture with the preform to a flow of gaseous precursor, the gaseous precursor flowing into the working region and infiltrating the fiber preform to deposit a coating on the fiber preform, wherein the seal blocks a gap between the border mate faces to limit inflow of the gaseous precursor through the gap into the working region so that the gaseous precursor must flow through the through-holes to reach the working region.