Browsing by Author "Raaif, M."

Samples of pure titanium were laser nitrided by continuous wave CO(2) laser irradiation in mixtures of nitrogen and argon gas with different ratios. In all cases, TiN formed in the surface. The properties and the characteristics of the processed samples were evaluated using a nanoindentation technique, optical microscopy, surface roughness measurements, x-ray diffraction and wear resistance measurements. It was found that the nitrogen content in the gas atmosphere has a massive effect on the microstructure and the mechanical properties of the laser nitrided samples. For all treated samples, the mechanical properties improve with the nitrogen content in the gas atmosphere. Moreover, the thickest TiN layers with high values of the microhardness and good wear resistance were obtained for the titanium sample that was treated in 80% N(2) and 20% Ar. In addition, the strain and the grain size of the coatings formed at the surface of the laser nitrided titanium samples were determined from x-ray data.

The present work reports on the effect of input plasma processing power in the range of 350-650W on the microstructure and mechanical properties of plasma nitrided Ti. The plasma processing time was 20 min and a gas mixture of 15% C2H2 and 85% N-2 was used. The characteristics of the carbonitrided layer have been investigated by microhardness measurements, surface roughness measurements, optical microscopy, and X-ray diffraction. The measured surface hardness values of the compound layer shows a maximum of 2050 HV0.1 for the sample treated at a plasma power of 550W. The thickness of the carbonitrided layer continuously increases as the plasma power increases. Moreover, the highest carbonitriding rate of 3.52 mu m(2)/s was observed when the input plasma power was adjusted at 600 W. This high carbonitriding rate of treated titanium samples is ascribed to the high concentration of active carbon and nitrogen species in the plasma atmosphere and the formed microcracks in the near surface of the sample during the plasma processing. (C) 2007 Elsevier B.V. All rights reserved.

The Ti-6Al-4V alloy was treated by inductively coupled rf plasma nitriding. The effects of plasma-processing time in the range of 5-35 min on the microstructure and the mechanical properties of the plasma-nitrided Ti-6Al-4V samples were studied. The plasma power input was adjusted at 450 W and pure N(2) gas was introduced to establish a treatment pressure of 8.0-8.4 x 10(-2) mbar. The characteristics of the nitrided layers have been investigated by microhardness testing, surface roughness measurements, optical microscopy, and x-ray diffraction. The results show that the surface microhardness increases as the plasma- processing time increases to reach 2000 HV0.1 at a plasma-processing time of 35 min. A high nitriding rate of 2.81 mu m(2) s(-1) at a plasma-processing time of 25 min was achieved. The formation of the hard phases TiN, Ti(2)N, and Ti( N) in the Ti-6Al-4V surfaces are found to be the reason for the increased microhardness. Surface energy, yield strength and Young's modulus for the nitrided Ti-6Al-4V alloy were calculated from the Vickers microhardness data.

Inductively coupled radio frequency plasma surface treatment was applied to commercially pure titanium sheets. The goal was to increase the efficiency of the carbonitriding process, i.e., to decrease the plasma treatment time to a few tens of minutes instead of several hours. The effects of different plasma-processing times on the microstructure and mechanical properties of plasma-carbonitrided Ti were examined. The characteristics of the carbonitrided layer were investigated by microhardness testing, surface roughness measurements, optical microscopy and X-ray diffraction. The surface microhardness and the thickness of the compound layer of carbonitrided Ti increase with the plasma-processing time. Surface energy, yield strength and Young's modulus for carbonitrided titanium were calculated from the Vickers microhardness data. An attempt was made to interpret the high carbonitriding rate and the high microhardness values of carbonitrided titanium with respect to previously published results.