Detonation-gun (D-gun) sprayed alumina-based ceramic composites as mono-layered and functionally graded coatings (FGC) are evaluated. The coatings are subjected to three-point bending test to assess their flexural response. The results show that among the depositions, monolayer alumina-titania deposition exhibits better flexure characteristics compared to the functionally graded coatings. Copyright © 2011 Inderscience Enterprises Ltd.

Lakshmanan Vijayaraghavan

M. M. Mayuram

Ramalingam Krishnamurthy

Characterisation

D-GUN

FRACTOGRAPHS

FUNCTIONALLY GRADED COATINGS

Acoustic emissions

Ceramic materials

Detonation

Monolayers

Powder metallurgy

Sprayed coatings

Titanium dioxide

Composite coatings

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Investigations on flexural characteristics of functionally graded alumina and alumina-titania ceramic composite coatings

International Journal of Materials and Structural Integrity

The fracture toughness of the as plasma sprayed alumina-13 wt.% titania (AT-13) coatings was evaluated using micro-indentation techniques. Indentations with smaller loads of 0.49 N show features such as partially melted particles to be extremely hard and brittle. However, the matrix made up of bi-modulus microstructure of splats was much tougher due to operative toughening mechanism for instance, crack bridging, which effectively retarded propagation of the cracks. Log plots of crack length (C) versus load (P) for loads varying from 1.96 to 9.8 N occurred with a slope of 0.65 ± 0.095 signifying sub-surface median or palmqvist type cracks to be rampant. The as sprayed microstructure made of pores; partially melted particles and splats were found to be anisotropic with regard to indentation toughness. Cracks were found to initiate and propagate easily in direction parallel to the coating growth directions than along the splat boundaries. Accordingly the bonding between the splats caused by plasma spray process could be deemed to be superior. The preferential directionality developed in the microstructure due to the imposed heat flow conditions essentially has weakened the microstructure. © 2005 Elsevier Ltd. All rights reserved.

Journal of the European Ceramic Society

Evaluation of fracture toughness of as plasma sprayed alumina-13 wt.% titania coatings by micro-indentation techniques

The life of mechanical components used for tribological and other applications, where surfaces are exposed to different types of loading, can be significantly enhanced through deposition of ceramic/ceramic composite on the surfaces. Among various spray deposition techniques, plasma spraying is most widely used. However, coatings developed through this technique need to be evaluated for performances under different conditions. The main aim of the present investigation is to study the response of the plasma-sprayed alumina-titania (AT-13) ceramic composites subjected to high frequency impact loading, in both as-sprayed and microwave-treated (post-processed) conditions in terms of indentation scar dimension and acoustic emission (AE) signals emitted by the impulsed material. The significance of AE monitoring for evaluation of critical load and duration for the onset of cracking of spray deposits is illustrated. Results show critical load and duration for the onset of cracking as 10 N and 3 min, respectively, in both cases. Results are discussed with illustrations. © 2002 Elsevier Science B.V. All rights reserved.

Materials Letters

Response of plasma sprayed alumina-titania ceramic composite to high frequency impact loading

The response of the plasma-sprayed alumina-titania ceramic coating was evaluated in terms of depth of penetration as influenced by material hardness and applied load, crack propagation and also acoustic emission (AE) signal emanated by the sprayed material under stress. The possibility of evaluating mechanical properties of sprayed ceramics from the depth sensing indentation test is illustrated in the paper. The significance of AE monitoring for critical load evaluation and also material response is illustrated in the text. Also AE monitoring was found to be effective in determining the critical load for cracking of sprayed ceramics.

Response of plasma-sprayed alumina-titania composites to static indentation process

Surface and Coatings Technology

Plasma-sprayed oxide ceramics on steel substrates

Thin Solid Films

Bonding of detonation-sprayed coatings

Journal	International Journal of Materials and Structural Integrity
ISSN	17450055
Open Access	No