Microstructure and properties of gas atomized UHCS compacted by HIP and SPS

Ultra-high carbon steels (UHCS) are hypereutectoid steels containing 1.0-2.1% carbon. Exceptional mechanical properties have been reported in materials processed to fine ferrite grains with fine spherical carbides. In this study UHCS C 1.6, Al 1.67, Cr 1.28, Si 0.72, Mn 0.72 wt.-% was cast and hot rolled (HR), hot isostatical pressed (HIP) and spark plasma sintered (SPS). Microstructures, phase structures and mechanical properties were compared. Processing parameters affect the microstructure considerably. HIP and SPS materials had with optimum parameters fine spherical carbides and fine-grained ferrite/perlite structure. Hot rolled material had coarser microstructure with large ferrite grains. Hot rolled material had higher hardness and lower elasticity than PM-materials. Heat-treated materials were also compared using hardness testing and tensile testing.