Evaluation of theoretical models describing the scratch adhesion test based on experimental results

ABSTRACT

The article presents theoretical analyzes and results of research work on the verification of a commonly used method for measuring the adhesion of thin hard and superhard coatings applied to the blades of cutting tools made of various materials. The paper contains descriptions of the scratch adhesion test, taking into account, inter alia, interfacial shear stress model, energy model and friction model. This method of measuring the adhesion of the coating to the substrate has been presented in theoretical analyzes as a means of transmitting the appropriate amount of mechanical force or energy necessary to detach the coating from the substrate. The article discusses three approaches to describe the scratch adhesion test. The presented approaches concern: 1) “delivering” the critical shear stresses in the transition layer between the coating and the substrate according to the Benjamin and Weaver model, 2) “providing” additional elastic energy according to the Lauger model (according to the energy balance equation), 3) taking into account the criterion of deformation and matching of the coating to the substrate in the place of the indentation in the Burnett and Rickerby model by using the interfacial restraint parameter $\chi$. The above-mentioned theoretical models have been experimentally verified for coatings deposited on substrates (cutting blades) made of high-speed steel, sintered carbides, white (oxide) tool ceramics, black tool ceramics (mixed, oxide-carbide), and cubic boron nitride. The tests of the adhesion force were performed with the use of proprietary equipment. This device is equipped with two channels for acoustic wave measurement by using a sound level meter and vibration measurement by a piezoelectric transducer. The adhesion force at which detaches the coating from the substrate was estimated by measuring the actual value of the amplitude of the vibration acceleration signal, its absolute value and the vibration signal intensity. The obtained values were verified using images from the profilometer and scanning electron microscope (SEM). In the final part of the article, the described models were verified on the basis of own experimental research and conclusions were formulated resulting from the analyzes and comparisons made. So far, mentioned models have not been assessed in terms of which of them allows the most accurate determination of the actual value of the critical load for the selected coating-substrate system. This was done in this article on the basis of own research. This innovative approach is a basic achievement.

KEYWORDS:

• Adhesion
• scratch test
• coatings
• cutting tools

Acknowledgments

The author would like to thank the Institute of Mechanical Technology of Poznan University of Technology for the financial support (project No. 0614/SBAD/1565).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Politechnika Poznańska [project No. 0614/SBAD/1565].