Abstract
Present paper describes application of four points bending tests to investigate fatigue and fracture of Al-Al_2O_3-CrC coating. The crystallographic and morphological texture was characterized and the fracture resistance was measured. CrC nanoparticles improve fracture resistance of aluminum oxide coating. CrC nanoparticles produced by the pyrolitic deposition technique effectively heal pores and defects of aluminum oxide coating. It results in high fracture resistance. The experiments showed that in all cases, the detection of an acoustic signal corresponded to the appearance of a circular cracks seen on the surface; in a very few cases, examination of the surface after detection of a signal revealed the presence of two ring cracks. The number of healed defects and the effectiveness of the individual healing determine the degree of toughening associated with crack healing. Micromechanical models using arrays of internal or surface cracks have been developed. The models provide mechanics of deformation and failure for the coating. This micromechanical model gives a reasonable explanation for the observed fatigue crack growth. Based on these theoretical findings it would appear that the technique has a great potential for studying of the fatigue properties of coatings based on oxide ceramics and chrome carbide nanoparticles.
