Slurry Sprayed Mullite Coatings and Their Corrosion Performances

Slurry Sprayed Mullite Coatings and Their Corrosion Performances

Rajeev Verma (PEC University of Technology, India), Narendra Mohan Suri (PEC University of Technology, India) and Suman Kant (PEC University of Technology, India)
DOI: 10.4018/978-1-5225-4194-3.ch008


Slurry spray technique (SST) is a distinctive variant among the numerous and already established coating techniques. Functionally graded thermal barrier and environmental barrier coating have been the functionalities developed so far for the process. Among the choice of the various ceramic feedstocks available mullite and partially stabilized zircona have been found suitable and investigated for the coating deposition via SST. This chapter reports the findings of the corrosion studies in simulated industrial corrosive environments and characterization results of the six sets of slurry sprayed mulite-nickel based coatings. Decent protection against coating has been found during the immersion test performed on these coatings for evaluating their corrosion performance. The developed coatings are recommended for use in applications to endure the elevated temperature and inflict corrosion. Thermal cycling test was performed to support the acceptable thermal shock resistance and coating compliance of the developed coatings.
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Over the past three decades, many fabricating methods have been developed for depositing ceramics and other coating materials on a metal substrate. All these fabricating techniques can be categorized into three main groups: deposition techniques, flame spray techniques, and bulk processes (Kieback et al, 2003). Each fabrication method differs from each other considerably, in the context of physical principal utilized, cost, and intricacy. However, the main hindrance in the pervasive utilization of these techniques is the sophisticated equipment and thus manufacturing cost involved. Besides, most of these already established fabrication methods have not been effective in large curved areas. Despite, the existence of pre-established and consolidated deposition techniques, an active research fraternity strives for novel and cost-effective alternatives, both for the method and feedstock materials. Moreover, the use of low fabrication cost stages and the possibility to utilize the industrial waste makes it easy to imagine the potential material and cost saving offered by SST. Slurry spray technique (SST) is conceived to be as an analogous to the thermal spray coating regime, because of the use of thermal energy required for sintering of the powder constituents. SST being relatively facile and unutilized deposition technique requires supplementary research efforts for it to make commercially viable.

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