Hypoeutectic Fe-Cr-Ni-Mo-C alloys additionally strengthened by the Frank-Kasper phases - Design by means of the CALPHAD approach

In the present work, the concept of hypoeutectic Fe-Cr-Ni-Mo-C alloys additionally strengthened by the Frank-Kasper phases is shown. The alloys were designed using the CALPHAD approach in order to obtain a matrix with high corrosion resistance, similar to that of stainless steels, and good wear resistance at room and elevated temperatures, achieved by the precipitation of eutectic carbides and the Frank-Kasper phases. The main design strategy is to produce alloys with a narrow solidification range and precipitations of the Frank-Kasper phases within the dendrites after heat treatment in order to reduce the mean free path of the matrix. The effect of molybdenum on the evolution of intermetallic phases in the Fe-25Cr-xMo-0.8C system was determined. Additionally, the influence of nickel in the Fe-25Cr-5Mo-xNi-0.8C system on phase composition of the matrix, as well as the stability and volume fraction of intermetallic phases were investigated. Lever-Rule and the modified Scheil-Gulliver solidifications were simulated for selected five alloys in order to investigate the phase precipitation sequence. Particular emphasis during the discussion was placed on the influence of Mo and Ni on phase stability, as well as solidus and liquidus temperatures in the investigated systems.