Powder metallurgy is a classic discrete component fabrication process that relies on the flow of metal particles into a die cavity, where the powders are compressed into a preform that is subsequently sintered. Current technological limitations trace to the inability to achieve undistorted, full-density parts. For example, density gradients induced from shaping processes lead to nonuniform shrinkage during sintering. Thermal debinding, used to remove binders prior to sintering, introduces defects or shape distortions: subsequent sintering exacerbates the situation. High temperature sintering can produce full density microstructures, but dimensional accuracy decreases as powder particle size increases. Supersolidus liquid phase (SLP) sintering offers an alternate processing method for high-alloy materials, but thermal protocols are not well understood. Thus, the industrial protocol has been to work from historical data and iterations to specify tooling and processing cycles to produce target components.
Our research addresses these barriers by forming a team with complementary skills in powder metallurgy, ultrasonic inspection, binder/lubricant technology, and computer-based design in manufacturing/processing. Tool steel and 316L stainless steel powder parts with axisymmetric geometries will be the focus of the investigations. A set of protocols will be established to reduce the dimensional variability that arises at two key processing steps: debinding (low temperature), and SLP (high temperature) sintering. We will establish thermal cycle guidelines to achieve distortion free, full density components. Furthermore, the investigation will produce a resource of constitutive models, increase the understanding of the microstructure evolution, and advance the development of ultrasonic techniques to evaluate full-field density and detect defects throughout the process cycle. The educational plan includes integrating undergraduate and graduate student experiences across the breadth of the research tasks. The creation of design tools for the powder processing industry will be a significant advance for industry, and it will be disseminated to some 90 industrial companies from materials suppliers and equipment manufacturers to part fabricators and end users.
|Effective start/end date||8/1/02 → 7/31/05|
- National Science Foundation: $500,000.00