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Search for alloys with improved high temperature specific strength and creep resistance properties for aerospace applications has led in the last decades to sustained research activities to develop new alloys and/or improve existing ones. The maraging steels evoked tremendous interest, especially in the aerospace world. Extra low carbon, high nickel, iron based alloys held great promise of providing an extraordinary combination of structural strength and fracture toughness. Applications of this alloy include aircraft structural components and rocket engine case for Satellite Launcher Vehicles. The objective of this work is to study the creep behavior of a solution treated Maraging 300 alloy. Constant load creep tests were conducted with this alloy at 550°C and in a stress range of 200 to 500 MPa. The creep parameters are determined. Samples with a gage length of 18.5 mm and a diameter of 3.0 mm were used for all tests.

The present study concerns laser surface nitriding of Ti-6Al-4V. The Ti-6Al-4V alloy was submitted a superficial treatment of pulsed laser Nd:YAG (λ=1.064 μ\m) in atmosphere of 40wt% nitrogen-60wt% argon. The samples were characterized by optical microscopy and electron scanning microscopy. The microstructure of the surface nitrided Ti-6Al-4V consists of TiN dendrites distributed in α--Ti matrix. It can be noted that there is a significant enhancement in surface roughness after surface nitriding (6.60 μm) as compared to the as received Ti-6Al-4V (0.46 μm). The microhardness of the surface is improved to 1100 VHN as compared to the 340 VHN of substrate.

The objective of this work was evaluating the microstructure of the Ti-6Al-4V alloy in creep test. Yttria stabilized zirconia with a CoNiCrAlY bond coat was atmospherically plasma sprayed on substrate. Constant load creep tests were conducted with alloy in air and in nitrogen atmospheres at stress level of 319 MPa at 600°C. The microstructural analyze shows that the predominant mechanism in the test conditions was characterized by formation and coalescence of microcavities with shape and size varieties. The size and shape of dimples are governed by number and distribution of nucleated microcavities and by stress internal level present in material.

The aim of this paper is to study of oxidation effects in creep of the Ti-6Al-4V alloy, in different atmospheres (air, nitrogen and argon). The samples were treated during 24 hours at 600°C in different atmospheres The samples treated during 24 hours at 600°C and the oxidation behavior in each atmosphere was observed. The oxidation was more aggressive in air atmosphere, forming TiO2 film in the surface. The alloy was tested in creep at 600°C in argon, nitrogen and air atmospheres using 250 MPa. The behavior of creep curves shows that useful life is better in atmospheres not so oxidant.

The objective of this work was to evaluate the creep behavior of the Ti-6Al-4V alloy focusing on the determination of the experimental parameters related to the primary and secondary creep stages. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V substrates. Constant load creep tests were conducted with Ti-6Al-4V alloy in air for coated and uncoated samples and in nitrogen atmosphere for uncoated samples at 500°C to evaluate the oxidation protection on creep of the Ti-6Al-4V alloy. Results indicated the creep resistance of the coated alloy was greater than uncoated in air, but nitrogen atmosphere was more efficient in oxidation protection.