ScienceAsia 32 (2006): 411-416 |doi: 10.2306/scienceasia1513-1874.2006.32.411

Finite Element Analysis of the Critical Ratio of Coating Thickness to Indentation Depth of Soft Coating on a Harder Substrate by Nanoindentation

Nurot Panich^1*, Panyawat Wangyao¹, Thoedsak Chomtohsuwan² and Sun Yong³

 
ABSTRACT: This study presents the critical ratio of coating thickness to indentation depth (CRTD) of a soft coating on a harder substrate by nanoindentation. The indentation processes were simulated with the finite element (FE) software programme. In the FE model, the influence of the yield strength ratio (Yc/Ys) and the indenter tip radius (r) have been investigated. In addition, the critical ratio of coating thickness to depth at which the substrate effect is less than 5% has been presented. It was found that increasing Yc/Ys and tip radius increases the CRTD. Furthermore, the CRTD is strongly dependent on the allowable degree of substrate effect. For example, when the substrate effect is increased from 5% to 10%, the CRTD is considerably reduced. Based on the FE calculations, an empirical equation has been derived in terms of the effect of substrate to determine the critical indentation depth when yield strength ratio is between 0.1 and 0.8 and the indenter tip radius is between 0 and 2 mm.

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¹ Metallurgy and Materials Science Research Institute, Chulalongkorn University, Bangkok 10330, Thailand.
² Faculty of Economics, Chulalongkorn University, Bangkok 10330, Thailand.
³ School of Engineering & Technology, De Montfort University, Leicester LE1 9BH, UK.

* Corresponding author, E-mail: panich@pmail.ntu.edu.sg

Received 4 Feb 2005, Accepted 17 May 2006