Thermodynamic analysis of oxidation during selective laser melting of pure titanium

Purpose When a pure titanium component is fabricated in a selective laser melting (SLM) process using titanium powder, the oxygen concentration of the SLM sample increases compared to the initial powder. The purpose of this paper is to study the reason for increasing oxygen concentration after SLM. Design/methodology/approach To understand this phenomenon, the authors analyzed the oxidation behavior during the SLM process thermodynamically. Findings Based on the laser parameters used in this study, the temperature of the Ti melt during the SLM process was expected to rise to 2,150°C. Based on the thermodynamic analysis, the equilibrium oxygen partial pressure for oxidation was 2.32 × 10−19 atm at 2,150°C when the dissolved oxygen concentration in the titanium is 0.2 wt.%. However, the oxygen partial pressure inside the SLM chamber was 1 × 10−3 atm, which is much higher than the equilibrium oxygen partial pressure. Therefore, oxidation occurred during the SLM process, and the oxygen concentration of the SLM sample increased compared to the initial powder. Originality/value Most studies on fabricating Ti components using additive manufacturing (AM) have been focused on how the changes in the microstructures and mechanical properties depend on the process parameters. However, there are a few studies that analyzed the oxygen concentration change of Ti during the AM process and its causes. In this study, the authors analyzed the oxidation behavior during the SLM process thermodynamically.

Iron Oxidation State Analysis in ESR Slag

It is shown that the value of the equilibrium oxygen partial pressure,Po2as a value available for measurements is possible to be taken as a measure of slag redox potential of, taking into account its electronic system performance. Application of the electromotive force method (EMF) allowed establishing the character of a change in the average oxidation state of iron νFedepending onPo2, the temperature and slag composition. The study of Mössbauer absorption spectra of quenched slag samples confirmed the possibility of simultaneous presence of iron in the flux in oxidation states from 0 to +3.

The interfacial reaction in Cr3C2/Al2O3 composites

This study investigates the effects of sintering atmosphere and temperature on the interfacial properties of Cr3C2/Al2O3 composites. Thermodynamic considerations and calculations with computer-assisted methods for the equilibrium compositions in the Al–O–Cr–C system were used to simulate the interfacial reaction in Cr3C2/Al2O3 composite during sintering. The results were in good agreement with the experimental analysis. Cr3C2 is more stable during sintering in a system with carbon due to the lower equilibrium oxygen partial pressure. Controlling CO and O2 gas concentration, Cr3C2 first oxidized, decarbonized, and then transformed to Cr7C3 before reacting with Al2O3. An interfacial reaction between Cr3C2 and Al2O3 was not observed.