Depth-sensing Indentation Measurements Research Articles

A contribution to the mechanical characterization of polymeric coatings by depth-sensing indentation measurements

Coating-substrate systems consisting of polypropylene coatings with thicknesses of 6 and 9.8 μm on silicon are investigated by depth-sensing indentation measurements with end loads between 20 and 1000 mN. Different effective load rates were applied. The results are correlated to an energy- and volume-related interpretation of the deformation processes. The proposed model permits to proof constant material behaviour over extended penetration depths. The potential on the quantification of the viscoelastic character as well as on the compound strength must be further verified.

Coating and interface characterization by depth-sensing indentation experiments

The basic principles of coating and interface characterization by an energetic evaluation of depth-sensing indentation measurements are summarized and presented together with a review of recent experimental results. The considered coating—substrate systems are ceramic-like coatings, such as TiN on less hard substrates such as high speed steel. Effects of internal compressive stresses of the coatings on the results of the energetic evaluation are illustrated by experimental results. Internal stress, hardness equivalent, coating thickness and a specific threshold energy for interface deformation are discussed as parameters for the quantitative design of hard coating architectures.

Elasto-plastic properties of IBAD TiN films made under off-normal incidence

For the IBAD coating of practical 3-D samples, effects of off-normal ion incidence on thin film properties have to be studied. Different growth conditions lead to different film microstructures. Thin films of TiN, made by reactive IBAD using a 12 kV argon beam, have been grown with an ion-to-atom ratio varying from 0 to 0.14 and an ion-beam incidence varying from normal to 55 ° off-normal. The elasto-plastic properties of the films were determined by analysing the data from depth-sensing indentation measurements. Three different types of behaviour are observed, corresponding to different kinds of microstructures. Hardness and Young's modulus of the films are dependent on the growth conditions. The consequence for practical applications of coatings of complex shape is that only carefully designed object-handling can prevent inhomogeneous film properties.

Quantification of the interface strength between (Ti,Zr)N coatings and high speed steel

The interface strength of physical vapour deposited (Ti,Zr)N coatings was determined by qualitative evaluation of the spallation patterns around Rockwell C indents as well as by differential load feed analysis of depth-sensing indentation measurements. Varying values of interface strength were produced by different wet cleaning procedures of the high speed steel samples prior to magnetron sputtering. The results of both evaluation techniques were comparable. The highest interface strength was determined for electrochemically enhanced wet cleaning with acidic neutralization.

Elastic constants of WC-a-C:H composite films studied by Brillouin spectroscopy.

Brillouin light-scattering experiments have been performed on tungsten-carbide containing amorphous-hydrogenated-carbon (WC\char21{}a-C:H) films which were prepared on (111) silicon wafers by a reactive rf sputtering process. From the measured velocity of the Rayleigh surface modes the shear modulus G is calculated as a function of the tungsten-carbide volume fraction, reflecting a phase transition of the films from an a-C:H-dominated to a crystalline \ensuremath{\beta}-WC-dominated WC\char21{}a-C:H mixture. The elastic constants determined agree well with results obtained from depth-sensing indentation measurements. Theoretical calculation of the elastic constant of the composite was also performed as a function of WC volume fraction. The results show a small deviation from the experimental data in the range of low WC fraction, which is probably caused by the phase change of the a-C:H matrix. The relatively large discrepancy of the theoretical calculation in the high-WC-fraction region may be a result of the invalidity of the theory.