In-situ synthesis of titanium carbides in iron alloys using plasma transferred arc welding

The synthesis of Fe-TiC metal matrix composite during metal deposition with laser and arc welding techniques is of technical and economic interest for hard surfacing of engineering components. Recent studies linked the resistance to abrasive wear with the size and morphology of TiC precipitates, which are strongly dependent on the deposition conditions and, more importantly, on the alloy chemistry. In this study, the effect of silicon and manganese on the TiC precipitates was explored and different processing conditions were assessed. The characterisation included optical and scanning electron microscopy, X-ray diffraction and microhardness testing. The results indicate that silicon and manganese can have a significant effect on TiC size and morphology. Therefore, the composition of the matrix alloy offers an effective pathway to modify the microstructure of in-situ precipitated Fe-TiC metal matrix composites. © 2013 Elsevier B.V

Wear mechanisms and microstructure of pulsed plasma nitrided AISI H13 tool steel

AISI H13 tool steel discs were pulsed plasma minded during different times at a constant temperature of 400 degrees C Wear tests were performed in order to study the acting wear mechanisms The samples were characterized by X-ray diffraction, scanning electron microscopy and hardness measurements The results showed that longer nitriding times reduce the wear volumes. The friction coefficient was 0.20 +/- 0 05 for all tested conditions and depends strongly on the presence of debris After wear tests, the wear tracks were characterized by optical and scanning electron microscopy and the wear mechanisms were observed to change from low cycle fatigue or plastic shakedown to long cycle fatigue These mechanisms were correlated to the microstructure and hardness of the nitrided layer (C) 2010 Elsevier B V All rights reservedCNPq[142812/2006-4]CNPq[550316/2007-8]CNPq[573628/2008-4

The Nature and Origin of "Double Expanded Austenite" in Ni-Based Ni-Ti Alloys Developing Upon Low Temperature Gaseous Nitriding

International audienceGaseous nitriding of Ni-4 wt pct Ti alloy plates led to the development of double expanded austenite (gamma (N1) and gamma (N2)) at the surface of the nitride plates. Grazing-incidence X-ray diffraction analysis demonstrated that the component gamma (N1) is located close to the surface and the component gamma (N2) is located at a certain depth below the specimen surface, in correspondence with a layered character of the nitrided zone beneath the surface as revealed by optical microscopy. Electron probe microanalysis, atom probe tomography, and Laue microdiffraction analysis did not reveal a significant difference in nitrogen content of the gamma (N1) and gamma (N2) sublayers. By X-ray diffraction stress analysis it was shown that the only significant differences of the two expanded austenite layers is a pronounced difference in compressive stress parallel to the surface: the gamma (N1) layer is subjected to a huge compressive stress, as large as a few GPa, whereas a relatively modest stress prevails in the gamma (N2) layer