Manufacture of fatigue-resistant hollow articles

A method of manufacturing a hollow article, comprising the steps of:

• preparing at least two opposing parts of a hollow structure, the at least two parts being made of a titanium alloy and, when assembled, having an internal cavity therein;
• processing the at least two opposing parts, the step of processing including the steps of
• diffusion bonding the opposing parts together to form a bonded article, and
• introducing hydrogen from the interior of the internal cavity to the surface of the internal cavity, the step of introducing hydrogen occurring before, simultaneously with, or after the step of diffusion bonding;
• solution treating the bonded article at a solutionizing temperature in a hydrogen-containing solutionizing atmosphere;
• aging the bonded article at an aging temperature less than the solutionizing temperature in a hydrogen-containing aging atmosphere;
• and
• removing the hydrogen from the bonded article so that the hydrogen content at the surface of the internal cavity is less than a preselected amount.

A method of manufacturing a hollow fan blade, comprising the steps of:

• preparing at least two opposing parts of a hollow fan blade made of an alpha-beta titanium alloy, the at least two parts when assembled having an internal cavity therein;
• diffusion bonding the at least two opposing parts together to form a bonded article,
• heating the opposing parts to a temperature of from about 1020.degree. F. to about 1380.degree. F. in an atmosphere comprising a mixture of less than about 5 volume percent hydrogen in a carrier gas to introduce hydrogen from the interior of the internal cavity to the surface of the internal cavity, the step of introducing hydrogen occurring before, simultaneously with, or after the step of diffusion bonding;
• heating the bonded article to a temperature of from about 1245.degree. F. to about 1420.degree. F. in an atmosphere comprising a mixture of less than about 5 volume percent hydrogen in a carrier gas to solution treat the bonded article;
• heating the bonded article to a temperature of from about 930.degree. F. to about 1290.degree. F. in an atmosphere comprising a mixture of less than about 5 volume percent hydrogen in a carrier gas to age the bonded article;
• and
• heating the bonded article to a temperature of from about 1100.degree. F. to about 1400.degree. F. in an atmosphere that is substantially free of hydrogen to remove the hydrogen from the bonded article.

A method of manufacturing a hollow article, comprising the steps of:

• providing a titanium-alloy article having
• a body, and
• an internal cavity including a surface of the internal cavity;
• introducing hydrogen into at least a portion of a near-surface region of the internal cavity of the article but not into the body of the article at locations remote from the near-surface region;
• heat treating the article so as to form a fatigue crack initiation-resistant microstructure at the portion of the near-surface region of the internal cavity and a fatigue crack propagation-resistant microstructure within the body of the article;
• and
• removing the hydrogen from the article.