Effects of the substrate on the determination of thin film mechanical properties by nanoindentation

This paper reviews commonly used methods of analysing and interpreting nanoindentation test data, with a particular emphasis on the testing of thin films. The popularity of nanoindentation testing is evidenced by the large number of papers that report such measurements in recent years. Unfortunately, there appear to be several issues that are emerging as common sources of error in using this technique. The present paper is aimed at highlighting these errors for the benefit of those practitioners who wish to use the technique but are not fully conversant with the field.

Critical review of analysis and interpretation of nanoindentation test data

The hardness of a number of coated systems has been measured using a variety of experimental techniques ranging from traditional macro-Vickers indentation to ultra-low-load depth-sensing nanoindentation. This has allowed the hardness response to be measured over scales ranging from those less than the coating thickness, where a coating-dominated response is expected, to much more macroscopic scales where system behaviour is dominated by the substrate. The objective has been to construct a mathematical description of the hardness performance of coated systems which well describes the behaviour over this wide range of scales. Previous attempts at such quantitative descriptions have usually involved models focusing on some particular deformation mechanism (e.g. plasticity, elastic response or fracture). In contrast, this paper presents a new approach to analysing hardness data essentially using dimensionless parameters containing descriptors equally applicable to either plasticity- or fracture-dominated behaviour with all scales measured relative to the coating thickness. The model shows an excellent fit to a wide range of experimental data. Furthermore, once the fit has been made, not only can some deductions be made regarding dominant deformation mechanisms, but the model allows predictions of the contact response of other coated systems to be made.

On the hardness of coated systems

Design and evaluation of tribological coatings

To measure nanomechanical properties of surface layers of bulk materials and thin films, depth-sensing nanoindentation measurement techniques are used commonly. The nanoindentation apparatus continuously monitors the load and the position of the indenter relative to the surface of the specimen (depth of an indent or displacement) during the indentation process. Indentation experiments can be performed at a penetration depth of as low as about 5 nm. This chapter presents an overview of various nanoindentation techniques, various measurement options, and data analysis. Data on elastic-plastic deformation behavior, hardness, elastic modulus, scratch resistance, film-substrate adhesion, residual stresses, time-dependent creep and relaxation properties, fracture toughness, and fatigue are presented.

B. Jönsson

Papers

Hardness measurements of thin films

The use of fast heavy ions to improve thin film adhesion