The aim of this study was to optimize machining parameters to obtain the smallest average surface roughness (Ra) and flank wear (Vb) values as a result of the surface milling of a nickel-titanium (NiTi) shape memory alloy (SMA) with uncoated cutting tools with different nose radius (r_ε) under dry cutting conditions. Tungsten carbide cutting tools with different r_ε (0.4 mm and 0.8 mm) were used in milling operations. The milling process was performed as lateral/surface cutting at three different cutting speeds (V_c) (20, 35 and 50 m/min), feed rates (f_z) (0.03, 0.07 and 0.14 mm/tooth) and a constant axial cutting depth (0.7 mm). The effects of machining parameters in milling experiments were investigated based on the Taguchi L18 (2¹ × 3²) orthogonal sequence, and the data obtained were analyzed using the Minitab 17 software. To determine the effects of processing parameters on Ra and Vb, analysis of variance (ANOVA) was used. The analysis results reveal that the dominant factor affecting the Ra is the cutting tool r_ε, while the main factor affecting Vb is the f_z. Since the predicted values and measured values are very close to each other, it can be said that optimization is correct according to the validation test results.

The cold gas dynamic spray (CGDS) method has been considered a promising technology to produce a metallic bond coat for thermal barrier coating (TBC) systems. In this study, CoNiCrAlY bond coats produced by CGDS method were coated with yttria-stabilized zirconia (YSZ) by electron beam physical vapor deposition (EB-PVD). TBCs were subjected to 50 wt % V₂O₅ and 50 wt % Na₂SO₄ molten hot corrosion salt combinations at 1000 °C. In the case of YSZ top coat on TBCs, the reaction between Na₂SO₄, V₂O₅, and Y₂O₃ salts generates YVO₄ crystals, and these structures cause the transformation of tetragonal ZrO₂ to monoclinic ZrO₂. This situation occurs under operating conditions that lead to TBC failure. Hot corrosion behavior and the related failure mechanisms of TBC systems were investigated and discussed using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, and X-ray diffractometer (XRD).