Effect of substrate pretreatments on the structure and properties of AlTiN coatings deposited on TiCN-based cermets

Four different pretreatments (mirror polishing, grinding, sandblasting and acid washing) were performed on TiCN-based cermets substrates. Subsequently, AlTiN coatings were deposited on the four differently pretreated substrates by means of arc ion plating. The microstructure of AlTiN coatings were studied by scanning electron microscope and X-ray diffractometer. The results showed that the AlTiN coatings on differently pretreated substrates exhibited columnar structure with (200) preferred orientation. The columnar crystal of coatings coarsened with the increase of substrate surface roughness under the four pretreatments, and the thickness of the coatings increased. Scratch test showed that the adhesion strength of the AlTiN coating on the pickled substrate increased by 46.8% in comparison with that on the polished substrate. Wear test showed that the average friction coefficient of AlTiN coatings increased gradually with the increase of substrate surface roughness under the four substrate pretreatments. The AlTiN coating on the pickled substrate had the largest grain size and many voids. Therefore, the hardness was low and the wear resistance was poor. The AlTiN coating on the sandblasted substrate had the smallest grain size, and accordingly had high hardness and the best wear resistance.