Adhesion Analysis of Metallized Layer on Aluminium Nitride Ceramics by Scratch Test

In the present study, aluminium nitride (AlN) ceramics were metallized by conventional Moly-Manganese (Mo-Mn) process in the temperature range of 1200–1400oC for 20 min. The objective of the current study was to evaluate the adherence of the metallized layer on aluminium nitride ceramic surface by scratch test and pull-off test methods. Scratch testing is a simple and fast method of evaluating coatings qualitatively. The adhesion of the metallized layer with the substrate was evaluated by scratch testing technique at different loads ranging from 5 N-25 N. During the scratch test a stylus was moved on the sample surface with linearly increasing load. Optical microscopy was utilized to examine the width of the scratch track. The scratch test results showed that the metallization of AlN ceramics required a high metallization temperature for the formation of an effective, uniform metallized layer on them. The surface texture of the scratch track revealed that the width of the scratch track enhanced with increasing applied load. It was evident from the optical microscopy that during the scratch test, the material removal was increased with increasing the applied load when the metallization temperature was made constant while the material removal was decreased with the increase of metallization temperature for a constant applied load. The adhesion of the metallizing layer on the AlN ceramics was also evaluated quantitatively by a pull-off test using a stud pull tester. The adhesion strength of metallized (1400oC, 20 min) layer on the AlN substrate was 5 MPa at a force of 30.8 N. Both the scratch test as well as pull-off test indicated that the Mo-Mn layer metallized at 1400oC for 20 min showed the best adhesion strength.