Hot corrosion performance of LVOF sprayed Al2O3–40% TiO2 coating on Superni 601 and Superco 605 superalloys at 800 and 900°C

Abstract

Al 2 O 3-40% TiO 2 coating is deposited on Superni 601 and Superco 605 superalloys by low-velocity oxy-fuel (LVOF) process. LVOF sprayed coating is characterized for surface roughness, microhardness, scanning electron microscopy and X-ray diffraction analysis. Hot corrosion of the coated and uncoated superalloys have been evaluated in an aggressive environment of Na 2 SO 4-82% Fe 2 (SO 4) 3 under cyclic conditions at temperatures of 800 and 900 • C. The microhardness and surface roughness values of the as-sprayed coatings are found to be in the range of 742-946 Hv and 14.40-14.80 μm, respectively. Al 2 O 3-40% TiO 2 coating on both the superalloys has indicated protective behaviour during hot corrosion studies. Keywords. Superalloy; Al 2 O 3-40% TiO 2 coating; LVOF; microhardness; hot corrosion.

Cavitation Erosion Resistance and Wear Mechanism Model of Flame-Sprayed Al2O3-40%TiO2/NiMoAl Cermet Coatings

“…The results presented in Table 3 are in line with previous findings of the authors [15]. The hardness is in the range of hardness values presented in [2] for the LVOF-sprayed Al2O3-40%TiO2 coatings, but is lower than that of PS [10,11] or HVOF [12] Al2O3-TiO2 coatings. The relatively high value for the standard deviation of hardness values demonstrates that the coating microstructure incorporates porosity, voids, and defects formed by partially melted or unmelted powder particles, which is in agreement with metallographic results.…”

“…The Ra roughness parameter increases until the 50% cp content in the sprayed powder mixtures ( Figure 5) and then decreases with further increase of cp content. Moreover, the Ra value of the assprayed coating with 100% cp feedstock powder is comparable with the same type of top-layer coating studied by Mishra et al [2], which confirms that the spraying parameters of 100% cp were correct. The as-sprayed coating surface roughness is attributed to the presence of lamellar structure, the unmelted particles, and the overlapping of splats and it derives from spraying parameters and ceramic-to-metallic-powder ratios.…”

“…Aluminia-titania sprayed coatings, Al 2 O 3 -TiO 2 , are used in the chemical engineering, metal, and paper industries to improve resistance to wear, corrosion, and high-temperature oxidation [1][2][3][4][5][6]. The protective Al 2 O 3 -TiO 2 ceramic coatings are typically deposited with 3% [5,7,8], 13% [1,3,[8][9][10], 20% [3], 40% [2,3], or 50% [11] addition of TiO 2 .…”

“…Aluminia-titania sprayed coatings, Al 2 O 3 -TiO 2 , are used in the chemical engineering, metal, and paper industries to improve resistance to wear, corrosion, and high-temperature oxidation [1][2][3][4][5][6]. The protective Al 2 O 3 -TiO 2 ceramic coatings are typically deposited with 3% [5,7,8], 13% [1,3,[8][9][10], 20% [3], 40% [2,3], or 50% [11] addition of TiO 2 . Apart from the fact that plasma spraying (PS) is the most widely used technique of Al 2 O 3 -TiO 2 ceramic deposition [3,7,8,11,12], processes like flame spraying (low-velocity oxy-fuel LVOF) [2,5,6], high-velocity oxy-fuel (HVOF) [12], or even laser cladding [1] are also employed.…”

“…Apart from the fact that plasma spraying (PS) is the most widely used technique of Al 2 O 3 -TiO 2 ceramic deposition [3,7,8,11,12], processes like flame spraying (low-velocity oxy-fuel LVOF) [2,5,6], high-velocity oxy-fuel (HVOF) [12], or even laser cladding [1] are also employed. Among the above processes, LVOF is a low-power-consuming and, thus, cost-effective method, as compared with other thermal spraying techniques [2,9]. In addition, the Al 2 O 3 -TiO 2 sprayed coating structure produced by PS of HVOF [13,14] is well described in the literature.…”