Texturing of Magnetite Forming During Long-Term Operation of a Pipeline of 10CrMo9-10 Steel

摘要

The paper presents results of X-ray measurements of the texture of a magnetite (Fe_3O_4) layer formed on 10CrMo9-10 steel during 100,000 hours operation at the temperature of 575°C (in a flowing medium environment). The formed oxide layer was ～140μm thick. Measurements of texturing were performed on the oxide surface and also at the depth of ～50μm from the surface (1st polishing) and ～100μm (2nd polishing). X-ray studies were carried out using the radiation of a cobalt anode tube, λ_(Co)=0.17902nm, for (311) and (400) Fe_3O_4 reflections, using a radiation beam collimated to Φ=2mm. The study was aimed at determination of correlation between the texturing and the structure on the magnetite layer cross-section. A clear texturing of {111}<112> and {111}<110> type for the magnetite in the initial state and after the second polishing was found. Instead, after the first polishing there was a substantial texturing of {034}<100> and {015}<051> type. A different nature of the texture may result from a diversified morphology of magnetite at various depths (caused inter alia by a differentiated temperature on the tube wall cross-section during the material operation), which is related among other things to the crystallites size. The magnetite structure and texture changes can affect the magnetite porosity and cleavage.