Center for Heat Treating Excellence (CHTE)
Center for Heat Treating Excellence

Research Programs

Materials and Process Design for High-Temperature Carburizing

Funded by Department of Energy (DOE)

Research Team:
Professor Gregory B. Olson, Northwestern University
Professor Diran Apelian, WPI

A computational systems design approach pioneered at Northwestern University is being applied to the integrated design of materials and processes for the new technology of high-temperature carburizing. Motivated by goals of the ASM Vision 2020 Heat Treat Technology Roadmap, a new class of alloy steels specifically designed for high-temperature processing addresses greatly accelerated process cycles with reduced part distortion, while achieving substantial advances in fatigue and wear performance beyond the capabilities of conventional carburizing. The capability for order-of-magnitude increases in case depth also opens the way for tool and die applications not possible with previous case hardening technology.

Aided by accurate computational modeling of microstructural evolution over a hierarchy of length scales, prototype steels with designed nanostructures have demonstrated 1000VHN case hardness without primary carbides, showing substantial improvements in contact fatigue and wear life. Process studies on a new generation of alloy prototypes focus on the evolution of carbon pickup with boost cycle time at 1050C in low pressure propane. The data is being used to calibrate surface reaction kinetic models coupled to bulk diffusion simulations for process optimization and control. Plasma carburizing behavior is being investigated at CHTE for stainless grades of the new alloys as well as available commercial high-performance steels. Approaches to high temperature grain coarsening resistance include novel high-stability grain refining dispersions enabled by PM processing. New techniques are being developed for rapid measurement of case residual stress distributions using synchrotron Xray facilities of the Advanced Photon Source (APS) at Argonne National Lab to support final heat treatment optimization. Software tools are being combined to accurately address both multicomponent and multidimensional aspects of diffusion during carburizing and thermal treatment of actual components. Performance test plans include mixed contact/sliding and notch fatigue, with gear testing at NASA-Glenn under a related project. Preliminary trials in NASCAR racing gear application are already showing promising results.

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Last modified: September 06, 2007 11:13:08