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The effect of the addition of nickel, titanium, and nitrogen on the air oxidation behavior of W‐based sputtered coatings in the temperature range 600 to 800°C was studied. In some cases these additions significantly improved the oxidation resistance of the tungsten coatings. As reported for bulk tungsten, all the coatings studied were oxidized by layers following a parabolic law. Besides WO3 and WOx phases detected in all the oxidized coatings, TiO2 and NiWO4 were also detected for W‐Ti and W‐Ni films, respectively. WOx was present as an inner protective compact layer covered by the porous WO3 oxide. The best oxidation resistance was found for W‐Ti and W‐N‐Ni coatings which also presented the highest activation energies ( Enormala=234 and 218 kJ mol−1 respectively, as opposed to Enormala≈188 kJ mol−1 for the other coatings). These lower oxidation weight gains were attributed to the greater difficulty of the inward diffusion of oxygen ions for W‐Ti films, owing to the formation of fine particles of TiO2 , and the formation of the external, more protective layer of NiWO4 for W‐N‐Ni coatings.

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Titanium aluminides are used in the aeronautical and automotive field as an alternative material to manufacture critical components exposed to high temperatures and corrosive environments. These alloys due to its intermetallic structure exhibit some special properties such as low density, high strength, high stiffness, corrosion resistance, and creep resistance. When these components are manufactured, surface integrity is one of the most relevant parameters used to evaluate the quality of the parts. Severe surface integrity problems are reported in the literature, defects such as microstructural alterations, work hardening, residual stresses, surface cracks, among others induced by the cutting process. The surface and sub-surface alteration induced by machining are critical because it will affect the parts performance. Some parameters affect the quality of machined surface. In particular cutting parameters, cutting tools material, tool wear and material properties are the most frequently investigated. Experimental and empirical studies are presented mainly in order to understand the surface integrity induced by machining. This paper provides an overview of the problems associated with the machining process of various types of titanium aluminides. The cutting tools, machining parameters, as well as processing parameters employed to improve machinability and reduce surface defects in titanium aluminides are analyzed and discussed. Particular focus was given to turning and milling process of gamma titanium aluminides. Also, some of the optimal parameters for machining titanium aluminides are presented offering a compilation of the most relevant information from the first to the most recent works that analyze the different aspects that affect the machining of these alloys.

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