1986

During carbonitriding of iron-manganese alloys employing liquid salt baths with high alkaline cyanate content, the presence of an unknown phase, identified as an iron-manganese carboxinitride of the (Fe, Mn) (C, N, O,) type, was observed on the sample surfaces. This phase forms easily and in considerable amounts on treating alloys containing more than 20 wt. % of manganese at temperatures of about 850 K and for times higher than 10 hours.

Samples of UNI 39 NiCrMo 3 and 38 CrAlMo 7 steels have been nitrocarburized with two different proprietary processes, namely the Degussa's Tenifer-TF1 and the Hydromecanique and Frottement's Sur Sulf salt bath treatments. With the former process two different melt compositions were adopted, keeping the CN** minus ions content either at the 0. 5 or at the 4 wt pct level (treatments Tenifer-TF1 A and B). The top surface layer constitution, as determined by X-ray diffraction analysis, is reported for the two steels heat-treated in the Tenifer-TF1 baths in figs.

In the present work the possibility to obtain large size castings of compacted graphite cast iron by inoculating ipereutectic pig iron melts with Fe-Si-Ca-Mg-Ti alloys with different calcium contents was first studied. Two alloys have been used: the first contained 4 divided by 5, 5 wt % Ca and the second less than 1 wt % of the element. The amount of inoculant alloy to be added to the melts was calculated so that the content of Mg in the casting agreed with the Sofroni equation. Casting temperatures were in the 1350-1400 degree C range.

The use of infrared spectroscopy has shown that even the order involving a few unit cells can affect the crystalline solid reactivity. In the case of monocalcium aluminate hydration in the presence of a calcareous filler, it was possible to observe that an increase of carbonate lattice disorder caused a decrease of induction time and an increase of hydration rate of CA* * Cement Chemists' Notations: A = Al2O3; C = CaO; C = CO2; H = H2O - CaCO3 mixture and a change of developed phases mutual ratios.

Synthetic ferrous alloys containing chromium and/or nickel were prepared and borided at 1173 K with powders containing B4C, KBF4 and SiC for times varying from 20 to 60 h. The surface layers composed of borides of type (Fe, M)B and (Fe, M)2B were characterized by means of X-ray diffraction, microscopic observations, analysis with the microprobe and microhardness measurements. A quantitative study was carried out on the differentiated distribution of chromium and nickel in the phases constituting the borided layer.

In the present work the possibility to obtain large size castings of compacted graphite cast iron by inoculating ipereutectic pig iron melts with Fe-Si-Ca-Mg-Ti alloys with different calcium contents was first studied. Two alloys have been used: the first contained 4 divided by 5, 5 wt % Ca and the second less than 1 wt % of the element. The amount of inoculant alloy to be added to the melts was calculated so that the content of Mg in the casting agreed with the Sofroni equation. Casting temperatures were in the 1350-1400 degree C range.