Plasma sprayed Lanthanum zirconate coating over additively manufactured carbon nanotube reinforced Ni-based Composite: Unique performance of thermal barrier coating system without bondcoat

Abstract

For advanced thermal barrier coating (TBC) system in a modern aero and land based engine, there is pressing needs to impede the uncontrolled growth of thermally grown oxide (TGO) layers as well as the weight reduction of overall TBC system. To address both the issues, present study introduces a ‘bondcoat less’ TBC. Selective laser melting (SLM) technique has been used to fabricate two different substrates of composition NiCrAlY and NiCrAlY + 1 wt% carbon nanotube (CNT). Lanthanum zirconate (LZ) coating was deposited over the prepared substrate by plasma spraying technique. SLM processed NiCrAlY + 1 wt% CNT substrate showed the relatively higher increase in hardness and elastic modulus by 1.6 and 2.7 times, respectively. Top coat LZ coating and reinforced CNTs in NiCrAlY significantly suppressed the growth of the TGO layer at 1800 °C. It is shown that a fine microstructure, absence of pores in the coating and addition of CNTs in conjunction prevent the diffusion of the reactive species Al, Cr, Y from the NiCrAlY substrate towards the coating interface. Further, LZ coating despotised over NiCrAlY + 1 wt% CNT substrate was intact even after 48 cycles during the thermal shock resistance performed at 1800 °C.