Abstract
Utilization of gamma titanium aluminide alloys in aerospace and automotive/industrial applications has placed significant demand on melting sources for products to be used in cast, wrought, and direct-machining applications. There is also an increased demand for input stock used in gas atomization of powders. Current technologies used in ingot manufacturing include plasma arc melting, vacuum arc melting, and induction skull melting + centrifugal casting. Subsequent processing may include forging, re-melting + casting, or machining directly into components. Over the past six years, Arconic Engineered Structures has developed a robust melting method using plasma cold-hearth melting technology, including the design and implementation of a new 3-torch system to produce Ti-48-2-2 cast bars. General discussions concerning plasma cold-hearth melting, manufacturing challenges, and metallurgical attributes associated with cast Ti-48-2-2 bars will be reviewed. Emphasis will be on understanding the impact of hot isostatic pressing on internal voids, residual stress cracking and resulting mechanical properties.
Highlights
Next-generation aerospace propulsion systems are designed and manufactured to be more energy efficient
The large volume of titanium aluminide stock required to support the engine build rates is produced by a variety of methods, including VAR/ISM skull melting, and via plasma arc, cold-hearth melting (PAM) technologies
The present paper describes the PAM technology and provides a review of two significant manufacturing challenges associated with using this melting method for production of Ti-482-2 titanium aluminide bars
Summary
Next-generation aerospace propulsion systems are designed and manufactured to be more energy efficient. Utilization of gamma titanium aluminide low-pressure turbine blades represents one of many technologies that enable the GE LEAP and Pratt & Whitney Geared Turbofan (GTF) engines to achieve their respective performance targets [1]. LEAP LPT blades utilize Ti-48Al2Nb-2Cr machined from cast and heat-treated stock, while the GTF low-pressure turbine blades are produced from forged and heat-treated TNM alloy [2]. The large volume of titanium aluminide stock required to support the engine build rates is produced by a variety of methods, including VAR/ISM skull melting, and via plasma arc, cold-hearth melting (PAM) technologies. The complexity of gamma titanium aluminides presents many processing challenges, along with customer specifications impose very stringent requirements for qualifications and manufacturing procedures. The present paper describes the PAM technology and provides a review of two significant manufacturing challenges associated with using this melting method for production of Ti-482-2 titanium aluminide bars
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