G. Sambogna

Composition and structure of boride layers grown on low-manganese ternary iron alloys

Three Fe-C-Mn alloys containing 0.30, 0.60 and 1.35 wt % Mn, respectively, were laboratory cast and homogenized, borided for 4, 8 and 15 h at 850° C in contact with a B4C-base powder mixture and then studied by using surface Mössbauer spectroscopy. X-ray diffraction, metallography and microhardness measurements. The boriding depth and the properties of the reaction products were determined and discussed with regard to the manganese content in the alloys. The comparison with the results previously obtained for borided Fe-C-Ni and Fe-C-Cr alloys allowed some general features to be determined with regard to the coatings which can grow on iron alloys in contact with high power boronizing media.

Influence of chromium on boride coatings produced on iron alloys

Abstract The influence of chromium on the thermochemical boriding of iron alloys was studied by powder boriding a 13 wt.% Cr steel with mixtures with widely varying boron potentials and comparing the results with those obtained for low chromium and chromium-free alloys. The effects of chromium are discussed with respect to the total thickness of the coating, the morphology of the coating-substrate interface and properties such as the nature, crystallographic order and relative amounts and distribution of the reaction products.

Phase composition and structure of boride layers grown on laboratory-cast low-chromium alloys

Three Fe-C-Cr alloys containing up to 5.65 wt% Cr have been laboratory cast and homogenized, borided for 15 h at 850° C with a B4C-base powder mixture and then characterized by using surface Mössbauer spectroscopy, X-ray diffraction, metallography and microhardness measurements. The boriding depth and the nature, disposition and relative amounts of the reaction products have been determined and discussed with regard to the chromium content in the alloys. The mechanical compactness and hardness of the innermost Fe2B single-phase layers, which are quantitatively predominant in the boride coatings, have been related to the extent of crystallographic order.

Surface melting of a medium carbon steel by laser treatment

A 0.4wt% C normalized carbon steel has been graphite-coated and irradiated in air with a cw-CO2 laser beam at 1.3 kJ cm−2 to melt a near-surface layer of material. The solidified and the solid-state transformed regions have been investigated by means of surface Mössbauer spectroscopy, X-ray diffraction, metallography and microhardness measurements. Nature and morphology of the phases have been determined in each region, and their origin discussed in relation to the conditions of the treatment.

On the early stages of high purity iron boriding with crystalline boron powder

Metallographic analyses and surface Mössbauer measurements were carried out on high purity iron borided in a mild boronizing medium. It was found that, irrespective of the preliminary iron treatment such as annealing, carburizing or cold rolling, only a fraction of the exposed surface reacts with boron at 1000° C. The stratified arrangement and the average thicknesses of the different reaction products within the iron boride isles were determined. These results, as compared with those previously obtained for borided Armco iron, allowed the hypothesis of a mechanism for the thermal growth of iron borides.

On the early stages of oxidation of iron borides

Pure Fe2B and FeB powders were compacted and oxidized for 1 h in flowing oxygen in the 300°–450°C temperature range. The reaction products were analyzed by X-ray diffraction, surface Mössbauer spectroscopy and scanning electron microscopy. Thermogravimetric analysis was carried out on powders treated under the same conditions. Iron borides undergo oxidation at low temperatures, with formation of both oxides and oxygen-free products.

High temperature solid state reactivity between iron and chromium monoborides

AbstractPowder mixtures of FeB and CrB were compacted and then treated at 1000

Some effects of laser treatments on medium carbon steels

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