Low-temperature colossal supersaturation (LTCSS) is a novel diffusional surface hardening process for carburization of austenitic stainless steels and other alloys without the precipitation of carbides. The formation of carbides is kinetically suppressed, enabling extremely high or colossal carbon supersaturation. As a result, surface carbon concentrations in excess of 12 at.% are routinely achieved. This treatment increases the surface hardness by a factor of four to five, improving resistance to wear, corrosion, and fatigue, with significant retained ductility.

LTCSS provides a uniform and conformal hardened gradient surface with a hardness layer is at least 25µm thick, with a near surface hardness of ≈HV1200 (over 70 HRC). The thickness of the hardened layer can be increased further by additional carburization treatments. In addition, because parts are treated at low temperature, they do not distort or change dimensions. In addition to austenitic stainless steels, research efforts are underway to extend the technology to other industrially important alloys, such as precipitation-hardening stainless steels, duplex alloys, nickel-based alloys, and cobalt-based alloys.

This talk will describe the technology, and will discuss research findings from a recent U.S. Department of Energy project that quantified the performance improvements for treated materials.