Abstract
Isothermal oxidation testing of near α titanium alloys VT18U, VT20, Ti6Al7Nb and Ti6242S was performed in air at 560 °С for 1000 hours. Parameters of diffusion layer on the alloy surfaces were studied by microhardness indentations, optical microscopy, X-ray diffraction analysis and nuclear microanalysis. It was established that concentration of oxygen in diffusion layer of tested alloys after oxidation differs significantly. An approach was demonstrated and validated by nuclear microanalysis data that allows comparative evaluation of the total concentration of interstitial impurities in the diffusion layer by the X-ray diffraction method.
Highlights
A breakthrough development of high temperature tanium alloys in 1960-1970s inspired advancement of aircra - and enginebuilding
The minimum thickness of diffusion layer is observed in Ti6Al7Nb, the maximum thickness – in Ti6242S
The results of qualita ve X-ray diffrac on analysis (XRD) analysis demonstrate that the oxide scale consists of TiO2 ru le type, Fig. 3
Summary
A breakthrough development of high temperature tanium alloys in 1960-1970s inspired advancement of aircra - and enginebuilding. The new high temperature tanium alloys allowed crea on of new aerospace technologies, e.g. fully 93 percent of the legendary Blackbird’s structural weight consisted of tanium alloys [7] This aircra was designed and put into opera on in 1960s. It has been shown that high temperature alloys IMI834, Ti6242S, Beta21S, and Ti1100 exhibited deteriorated duc lity and fa gue strength a er opera on at elevated temperatures, when tested in the oxidized state [10,11,12,13,14,15]. There are s ll some open issues concerning rela onship between the main parameters influencing the metal (temperature, me, atmosphere, pressure) with its structural characteris cs (oxygen concentra on in metal, gas-rich layer thickness, material hardness, thickness, density and oxide adhesion, weight gain, diffusion coefficients, etc.) and mechanical proper es in the oxidized state (fa gue strength, duc lity, tensile strength). Oxida on was done in an electric laboratory furnace with a fan for air mixing and temperature maintenance within ± 5 ° C
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