One of the properties of PVD hard coatings that has an important influence on their tribological behaviour is the surface topography. This strongly depends on the topography of the bare substrate and the topography induced by the coating-deposition process (ion etching and deposition). In particular, the formation of growth defects significantly alters the surface morphology and the roughness. In this invited lecture, presented at the 13th interntional symposium on sputtering & plasma processes, the relationship between the growth defects and the tribological, corrosion and oxidation properties of PVD hard coatings is explained.
B.04 Guest lecture
COBISS.SI-ID: 28705831Defects are one of the major causes of coating failure during machining conditions. High local mechanical and thermal stresses on the defects result in high friction coefficients, sticking of workpiece material and in local delamination of the coating. Defect sites present structural weakness where corrosion and oxidation can be rapidly accelerated, sometimes resulting in catastrophic failure of the coating. In several scientific papers we have published findings on the origin and the formation of defects in coatings prepared by different PVD techniques (sputtering and evaporation). Research of defect concentration has an important economic benefit since reduction of defect concentration would lead to tools with longer lifetime and consequently to lower production costs. Due to my extensive work in this research area I was an invited lecturer on this topic at the prestigious International conference on metallurgical coatings and thin films in San Diego, USA (2013).
B.04 Guest lecture
COBISS.SI-ID: 26807335In invited lecture (22nd International Conference on Materials and Technology, 20.-22. october 2014, Portorož, Slovenia) the substrate surface topography as formed through the hard coating deposition process (polishing, ion etching, deposition) was described. On polished steel surface we found some topographical features which appeared at the positions of carbides and non-metallic inclusions. The reason is different removal rates of matrix in comparison with inclusions due to the difference in hardness. During the ion etching process the additional morphological features are formed. The reason is a difference in sputtering rate of inclusions and steel matrix. This resulting in a formation of shallow craters and hillocks, which increased the surface roughness for about three times. This could be one of the reasons why ion etching improves the adhesion of hard coatings efficiently due to mechanical anchoring. All these topographical changes of substrate surface reflected on the coating surface. Due to the shadowing effect they are often magnified through the coating. Thus inclusions in steel are sites at which the PVD nodular defects and pinholes are formed.
B.04 Guest lecture
COBISS.SI-ID: 28057127This volume of Thin Solid Films contains selected papers presented at the 16th International Conference on Thin Films that was held on 13–16 October 2014 in Dubrovnik, Croatia.
C.03 Guest-associated editor
COBISS.SI-ID: 29151015