**5. References**


d. By comparing hardness values it can be concluded that Al2O3 coating is harder than ZrO25CaO coatings. It can be also concluded that microhardness decreases with

e. It was found that erosion of coating systems occurred through spalling of lamella exposed on coating surface resulting from cracking along the lamellar interface. The material removal may occur from the displaced material forming lips around the indentations as a result of repeated impact of erodent. Erosion wear was more at 450 angle of impact showing that erosion behaviour as a composite ductile-brittle. Porosity influences erosion in three ways. Firstly, it decreases the materials strength against plastic deformation or chipping, since the material at the edge of a void lacks mechanical support. Secondly, the concave surface inside a void that is not under the shadow of some void edge will see an impinging particle at an angle higher than the average target surface to impact angle. This will be detrimental for brittle materials and beneficial for ductile ones. Finally pores can act as stress concentrators and decrease the

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[2] Sundararajan. G, *The solid particle erosion of metallic materials: The rationalization of the* 

[3] Sundararajan. T. and Roy. M. *Solid particle erosion behavior of metallic materials at room and elevated temperatures*, Tribology International, Vol. 30, 1997, pp 339-359. [4] Davis. J. R., *Surface engineering for corrosion and wear resistance*, ASM International. 2001. [5] Fagoaga, I, Viviente, J. L, Gavin, P, Bronte. J. M, Garcia. J and Tagle. J. A, *Multilayer* 

[6] I. M Hutchings, *Tribology: Friction and wear of engineering materials*, Metallurgy and

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[8] I. M. Hutchings, *Recent advances in the understanding of solid particle erosion*, Mecanique

[9] J. G. Murphy, H. W. King, M. L. Taylor, *Pariculate erosion of zirconia-alumina plasma* 

[10] R. Kingswell, K. T. Scott, S. Bull, *Erosion behaviour of plasma sprayed alumina coatings*, 2nd Plasma Technik Symposium, 1991, Lucerne, Switzerland, pp 367-377. [11] X. X. Zhang, I. M. Hutchings, T. W. Clyne, *The effect of deposition conditions on the Erosive* 

[12] B. R. Lawn, M. V. Swain, *Microfracture Beneath Point Indentations in Brittle Solids*, J. Mat.

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*influence of material variables,* Wear, Vol. 186-187, 1995, pp 129-144.

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obtained for ZrO25CaO coatings.

load bearing surface

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**5. References** 

increase in coating thickness and porosity.

lowest adhesion values. For the highest adhesion values, coating failure was mainly located in the bond coat/substrate interface. The highest value of adhesion strength was


**Part 3** 

**Coating Engineering** 

