T. S. Sidhu, A. Malik, S. K. Nath, Indian Institute of Technology, Roorkee, India; S. Prakash, Indian Institute of Technology, Roorkee, India, Roorkee, India
The present work evaluates the oxidation and hot corrosion resistance of high velocity oxy-fuel (HVOF) sprayed WC-NiCrFeSiB coating deposited on Ni-based superalloy (Superni 75) and Fe-based superalloy (Superfer 800H). The coated as well as uncoated specimens were exposed to air and molten salt (Na2SO4-25%NaCl) environment at 800 °C under cyclic conditions. The thermogravimetric technique was used to establish the kinetics of corrosion. The corrosion products were characterized using the combined techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe micro analyser (EPMA). The WC-NiCrFeSiB coating provides necessary resistance against oxidation and hot corrosion to both the nickel and iron based superalloys in the given environmental conditions at 800 0C. The oxides of active elements of the coatings, formed in the surface scale as well as at the boundaries of nickel rich splats, have contributed for the hot corrosion resistance of WC-NiCrFeSiB coatings, as these oxides act as barriers for the diffusion/penetration of the corrosive species through the coatings.
Summary: Hot corrosion is a serious problem in boilers, gas turbines, internal combustion engines and industrial waste incinerators. It consumes the material at an unpredictably rapid rate. As a consequence the load-carrying abilities of the components are reduced, leading eventually to their catastrophic failure.
The present research work is an attempt to evaluate the hot corrosion resistance of HVOF sprayed WC-NiCrFeSiB coating for their high temperature corrosive environment applications. The coating has been found successful in providing the resistance to the oxidation and the hot corrosion rate of Ni- and Fe-base superalloys at 800 oC.
We do hope that this paper will be of great interest to the readers of thermal spray community.
T.S. Sidhu
Corresponding author
tssidhu@rediffmail.com
