Investigation on structural Morphological nanomechanical and Tribological behaviour of ysz and ni Ysz based diffusion barrier coatings On nickel base superalloy prepared By electron beam evaporation Technique for nuclear applications

Abstract

Vitrification of high-level nuclear waste (HLW) is considered to newlinebe one of the important immobilization options today. This is carried out newlinein a suitable borosilicate glass matrix capable of hosting hazardous newlineradio-nuclides for a period of several thousands of years. The newlinevitrification process is done usually in a furnace or melter pot made up newlineof nickel base super alloy (alloy-690). The success of the technique newlinedepends on the quality of the nuclear waste glass produced and on the newlinelength of the uninterrupted service it can provide. However, the newlinecomponents of the vitrification furnace have been reported to degrade newlineprematurely due to molten glass-alloy interactions at high temperatures newlineand thereby increasing the volume of the metallic nuclear waste. The newlinework has been initiated with the main aim of fabricating a newlinecompositionally graded Ni-YSZ coatings to act as a diffusion barrier newlineunder high temperature and high-pressure environments for the newlineprotection of Inconel 690 components from harsh environments and to newlinemaintain the coating integrity. The current study involves three major newlineobjectives: (i) development of single layer of YSZ and five layers of newlinecompositionally graded Ni-YSZ coatings with various weight percent of newlineNi and YSZ using EBPVD technique under optimized process newlineparameters, (ii) study of structural, morphological, nanomechanical and newlinetribological behaviour of the coatings, and (iii) investigation on the newlineinter-diffusion effects of the fabricated nanocomposite coating with newlineborosilicate melt as a diffusion barrier material for high temperature newlineenvironments. newlinevii newlineThe stable cubic phase of YSZ was deposited at different substrate newlinetemperatures in the range of 473 - 973 K on Inconel substrates. The newlineenhanced hardness, reduced modulus, adhesion and tribological newlinebehaviour were found to be better for the coating deposited at substrate newlinetemperature of 973 K. Then this optimized temperature was fixed for the newlinedeposition of compositionally graded coating. Single layered Ni-YSZ newlinenanocomposite coating with varied weight percent of