Development of a high chromium martensitic steel proposed for roller bearing application

M. Faleschini, S. Peissl, Materials Center Leoben, Austria
G. Mori, CD-Laboratory of Localized Corrosion, Montanuniversität Leoben, Austria
S. Eglsäer, Boehler Edelstahl Gmb, Kapfenberg Austria

Abstract:
High chromium martensitic steels are designed to provide high corrosion resistance in combination with high strength. Some of these steel grades contain primary carbides for improving wear resistance, e.g. the steel 440 C. The present paper mainly deals with the effect of chemical composition and microstructure on corrosion and tribological properties of recently developed steels.

Different experimental alloys were produced in form of small ingots. The influence of the allying elements chromium, molybdenum and cobalt is investigated. The results indicate that corrosion resistance is improved compared to 440C.

Furthe investigations were focused on heat treatments, especially on tempering temperatures. They are very important for precipitation of secondary carbides, which worsen the corrosion properties. The carbide precipitation and chromium distribution was characterized by means of energy filtered transmission electron microscopy (EFTEM).

To characterize the wear properties of the developed steels, measurements with a Ball an Disc (BOD) tribometer under lubricated conditions were performed. The measured wear rates are comparable to M50, the standard bearing material for aircraft turbine bearings.

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