Mechanical Behavior Monitored by Acoustic Emission of Nanostructured Alumina–Titania Coatings

Abstract

This study aims to evaluate the mechanical behavior of nanostructured and conventional aluminatitania coatings by means of combining four-point bend tests monitored with acoustic emission. Determination of bending strength, along with information received from acoustic emission signal, such as quantity, amplitude, energy and length of events gives a better understanding of failure mechanisms in coatings. This information has been complemented with optical analysis of fracture surfaces. Failure of coatings has been observed to follow four stages that are clearly defined in the acoustic emission data. This fracture behavior has been observed for all three types of coating tested, but the nanostructured coating presented the best combination of hardness and strength, due to its duplex microstructure.