Influence of KCl and HCl on high temperature corrosion of HVAF-sprayed NiCrAlY and NiCrMo coatings. (15th June 2018)

• Record Type: Journal Article
• Authors: Sadeghimeresht, Esmaeil; Reddy, Liam; Hussain, Tanvir; Huhtakangas, Matti; Markocsan, Nicolaie; Joshi, Shrikant
• Is Part Of: Materials & design. Volume 148(2018)
• Page Start: 17
• Page End: 29
• Publication Date: 2018-06-15
• Subjects: Thermal spray coating -- NiCrAlY -- NiCrMo -- High-velocity air fuel (HVAF) -- Biomass-/waste-fired boiler -- Fireside corrosion; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2018.03.048
• Languages: English
• ISSNs: 0264-1275

Abstract

Highlights: HVAF-sprayed coatings were exposed to O2 +HCl atmosphere with and without KCl deposit NiCrMo exposed without KCl showed the lowest k p value (2.5×10 -7 mg 2 /cm 4 s) With KCl, k p was much lower in NiCrMo (1.3×10 -6 mg 2 /cm 4 s) than NiCrAlY (2.2×10 -5 mg 2 /cm 4 s). Formation of K2 CrO4 followed by Cl - were the main reasons of failure at the early stages of corrosion exposure. At the last stages, the protective chromia scale was interrupted due to the simultaneous presence of Cl - and Cl2 . Graphical abstract: Abstract: The oxidation performance of NiCrAlY and NiCrMo coatings thermally sprayed by high velocity air-fuel (HVAF) technique has been investigated in a chloridizing-oxidizing environment, with and without a KCl deposit, at 600 °C for up to 168 h. Both coatings protected the substrate in the absence of KCl due to formation of a dense Cr-rich oxide scale. In the presence of KCl, Cl − /Cl2 diffused through a non-protective and porous NiCr2 O4 scale formed on NiCrAlY, leading to formation of volatile CrCl3 . On the other hand, Mo in NiCrMo stimulated the formation of a more protective Cr-rich oxide scale which increased the corrosion resistance by reducing Cl − /Cl2 diffusion.