Status of Titanium Powder Metallurgy

An extensive research effort carried out in the last three years on the mechanical behavior of titanium alloy powder compacts has increased considerably the confidence in powder metallurgy (PM) products to the point that they can now compete directly with ingot metallurgy (IM) components in performance and reliability. Two major approaches are used in titanium powder metallurgy, the blended elemental (BE) and the prealloyed methods. The BE approach, which is a sintering method, provides a relatively inexpensive method for fabrication of components or mill products. The prealloyed method is aimed at high integrity complex shape components for demanding applications. The extensive mechanical property and microstructure studies have shown that for most mechanical properties, such as tensile strength, fracture toughness, and fatigue crack growth rate, the behavior of PM compacts parallels that of IM products with similar microstructures. In the past, the fatigue life of PM products was a major concern because of the possibility of early fatigue crack initiation associated with powder contamination. The present work demonstrates that control over powder cleanliness can increase the fatigue strength at least to wrought product level. The current commercial availability of cleaner prealloyed powders and producer awareness of the necessity for cleaner powder handling practices will further increase the performance and the reliability of titanium PM products. The expanded use of titanium in gas turbine engine parts, airframe components, surgical implants, computer printer parts and energy systems is increasing the demand for this net-shape technology which allows cost-effective production of high performance titanium complex shapes.