Carbon nanotubes stabilize high temperature phase and toughen Al2O3-based thermal barrier coatings. (1st September 2017)

• Record Type: Journal Article
• Authors: Ariharan, S.; Nisar, Ambreen; Balaji, N.; Aruna, S.T.; Balani, Kantesh
• Is Part Of: Composites. Number 124(2017)
• Page Start: 76
• Page End: 87
• Publication Date: 2017-09-01
• Subjects: Thermal barrier coating (TBC) -- Atmospheric plasma spraying (APS) -- Carbon nanotubes (CNTs) -- Transformation toughening; Composite materials -- Periodicals; Materials science -- Periodicals; Composite materials; Periodicals; Electronic journals; 620.118
• DOI: 10.1016/j.compositesb.2017.05.032
• Languages: English
• ISSNs: 1359-8368

Abstract

Abstract: In this work, alumina (Al2 O3 ) reinforced with zirconia viz., 0, 3, and 8 mol% yttria doped (i.e., ZrO2, 3YSZ, and 8YSZ), and 4 wt% carbon nanotube (CNT) are coated on Inconel 718 substrate by atmospheric plasma spraying (APS). Reinforcement by CNT and 3YSZ has led to a substantial enhancement in the fracture toughness from 3.89 MPa m 1/2 (for Al2 O3 ) to 5.90 MPa m 1/2 in the reinforced composite. It is observed that CNT has contributed ∼5–12% toughness enhancement, whereas ∼15% contribution to toughening is obtained via tetragonal to monoclinic ( t → m ) transformation of zirconia. Moreover, CNTs not only assist the t → m transformation but also enhance the toughness value of Al2 O3 -based thermal barrier coatings (TBC) near to its upper theoretical bound estimated using modified fractal model. Moreover, the effective thermal conductivity is estimated using modified theoretical models embracing the aligning factor of CNT in APS coatings, which unequivocally confirms the superiority of Al2 O3 reinforced with 3YSZ and CNT as a potential TBC. Graphical abstract: Highlights: Zirconia and carbon nanotube (CNT) reinforced aluminum oxide coating. Retention of high temperature t-phase zirconia phase by CNTs. Up to 51% fracture toughness enhancement with CNT and zirconia addition. Delineated fracture toughness contribution of CNT and t -ZrO2 using fractal model. Modified thermal conductivity model for oriented CNTs in plasma sprayed coatings.