Alternative Heat Treatments for Complex-Alloyed High-Cr Cast Iron Before Machining

Optimization of Thermal Processes Applied to Hypoeutectic White Cast Iron containing 25% Cr Aimed at Increasing Erosive Wear Resistance

“…Among the factors listed in Table 2, the meaning of factor C needs clarifying. This is a softening treatment aimed at facilitating the machining of this material before the hardening treatment [20]. This heat treatment consisted of 2 h at 1000 • C and 24 h at 700 • C. The goals of this treatment would be to destabilize the retained austenite and to seek a majority presence of perlite, thus facilitating hypothetical machining should it be necessary for the manufacture of industrial components using this material.…”

“…The redissolution of any possible cementite carbides precipitated during the softening treatment is, thus sought, thereby favoring the precipitation of Cr-rich secondary carbides and an increase in the Ms temperature so as to avoid the presence of retained austenite as far as possible after quenching [20]. The effect of a factor is defined as the variation in certain property of the material as a result of the variation of said factor.…”

“…Figure 2 shows the microstructure obtained following this treatment. Coalescence and thickening of the secondary carbides precipitated during the destabilization of austenite, prior to the isothermal dwell time at 700 °C, can be observed [20,23]. However, the measured hardness in this state reached an average value of 360 HV, which was greater than of the as-cast state.…”

“…The hardness of the cast iron in this state was 305 HV. One of the analyzed factors was the effect of a possible softening treatment designed to facilitate machining of this material with chip removal [20]. Figure 2 shows the microstructure obtained following this treatment.…”

“…From all the above, it follows that if the aim were to machine this material before its hardening by heat treatment, it would not be necessary to perform a prior softening treatment, contrary to what was concluded in a previous study on white cast irons containing 18% Cr. One of the analyzed factors was the effect of a possible softening treatment designed to facilitate machining of this material with chip removal [20]. Figure 2 shows the microstructure obtained following this treatment.…”