The titanium and aluminium investment casting expert TITAL GmbH was able to prove with a pilot batch that beta annealing as a special heat treatment for titanium investment castings is probably not necessary.
In doing so, TITAL takes up an adverse stance against the prevailing requirements of the aerospace industry. The industry requires the beta heat treatment for titanium components made of TiAl6V4 in order to achieve improved material properties especially regarding fracture toughness and crack propagation.
TITAL’s test report shows this procedure is not necessary with respect to the required material properties for titanium castings from TITAL.
Dr Ralf Gerke-Cantow, head of titanium production at TITAL, said: “The idea of beta annealing itself is good. Through the special heat treatment an extended durability of structural components shall be achieved with respect to crack propagation.
“Thus, inspection intervals shall be extended and costs shall be saved. However, for the castings in question it does not offer any additional effect.
“Now we can show by means of our research results that during the investment casting process a structure can be generated that has very good properties regarding fracture toughness and crack propagation.”
If this proves to be the case for titanium investment castings on a broader scale, beta annealing could be avoided which will lead to considerable cost savings as the required beta heat treatment process is very expensive. TITAL estimates costs per heat treatment cycle between EUR800 and EUR1,000.
TITAL has started additional metallurgical trial runs to further prove that beta annealing is not necessary for titanium investment castings from TiAl6V4 in order to achieve the required crack propagation requirements.
The investment casting specialists from TITAL have teamed up with the material experts from Airbus France and Airbus Germany to further verify the findings.
In addition, TITAL contracted the internationally well known testing laboratory Westmoreland, England, who also holds NADCAP certifications for the relevant processes. Additional test runs will follow soon to better understand the initial results.