Automatic and robust deposition process control to grow hard ncTiC/a-C:H coatings using industrial magnetron sputtering devices and tribological analysis of the titanium-carbon coatings

nc-TiC/a-C:H coatings consist of TiC crystallites embedded in an amorphous hydrogenated carbon matrix. Depending mainly on the chemical composition, the properties of these coatings can be tailored from hard coatings, with hardness of greater than 35 GPa to tribological coatings, with coefficients of friction lower than 0.1. In our research, we employed industrial PVD device of Platit equipped with a central titanium rotating cylindrical cathode. Titanium was sputtered in a mixture of argon and acetylene. At critical acetylene supply, a sudden drop in the cathode voltage was observed. This sudden change in the plasma parameters was mirrored in chemical composition and mechanical properties of the deposited coatings. Close to critical acetylene supply, the highest coating hardness of 35 GPa was obtained. The critical acatylene supply shifts as the target get eroded. In our work, we suggest the fully automatic, robust and reliable procedure to deposit hard nc-TiC/a-C:H coatings using the occurrence of the sudden plasma parameters change at critical acetylene supply to set the optimal deposition conditions. Further, the tribological analysis of the series of the titaniumcarbon coatings with different amount of amorphous carbon was carried out. We discovered, that the coefficient of friction strongly depends on humidity of the environment and we found, that the changes of the CoF during the tribological measurements are caused by the changes of the surface roughness

Comparison of Lifetime of the PVD Coatings in Laboratory Dynamic Impact Test and Industrial Fine Blanking Process

Protective hard PVD coatings are used to improve the endurance of the tools exposed to repeated impact load, e.g., fine blanking punches. During the fine blanking process, a coated punch repeatedly impacts sheet metal. Thus, the coating which protects the punch surface is exposed to the dynamic impact load. On the other hand, the laboratory method of dynamic impact testing is well known and used for the development and optimization of protective coatings. This paper is focused on the comparison of tool life and lifetime of the industrial prepared PVD coatings exposed to repeated dynamic impact load in the industrial fine blanking process and the laboratory dynamic impact testing. Three different types of protective coatings were tested and the results were discussed. It was shown that the lifetime of coated specimens in both the fine blanking and the dynamic impact processes was influenced by similar mechanical properties of the protective coatings. The qualitative comparison shows that the lifetime obtained by the dynamic impact test was the same as the lifetime obtained by the industrial fine blanking process. The laboratory impact test appears to be a suitable alternative for the optimisation and development of protective PVD coatings for punches used in the industrial fine blanking process

Automatic and robust deposition process control to grow hard ncTiC/a-C:H coatings using industrial magnetron sputtering devices and tribological analysis of the titanium-carbon coatings

nc-TiC/a-C:H coatings consist of TiC crystallites embedded in an amorphous hydrogenated carbon matrix. Depending mainly on the chemical composition, the properties of these coatings can be tailored from hard coatings, with hardness of greater than 35 GPa to tribological coatings, with coefficients of friction lower than 0.1. In our research, we employed industrial PVD device of Platit equipped with a central titanium rotating cylindrical cathode. Titanium was sputtered in a mixture of argon and acetylene. At critical acetylene supply, a sudden drop in the cathode voltage was observed. This sudden change in the plasma parameters was mirrored in chemical composition and mechanical properties of the deposited coatings. Close to critical acetylene supply, the highest coating hardness of 35 GPa was obtained. The critical acatylene supply shifts as the target get eroded. In our work, we suggest the fully automatic, robust and reliable procedure to deposit hard nc-TiC/a-C:H coatings using the occurrence of the sudden plasma parameters change at critical acetylene supply to set the optimal deposition conditions. Further, the tribological analysis of the series of the titaniumcarbon coatings with different amount of amorphous carbon was carried out. We discovered, that the coefficient of friction strongly depends on humidity of the environment and we found, that the changes of the CoF during the tribological measurements are caused by the changes of the surface roughness

On the significance of running-in of hard nc-TiC/a-C:H coating for short-term repeating machining

The importance of the often omitted running-in phase of tribological testing was studied on hard nc-TiC/a-C:H coating system selected as a representative of protective tribological coatings. The tribological measurements were periodically interrupted and the counterpart ball was replaced by a new one after every interrupted test to simulate machining applications, where the coatings are repeatedly in contact with a new material. The changes in the coefficient of friction and the wear rate of the counterpart ball were found to be dependent mainly on the roughness of the coating at any stage. It was found out that after substantial smoothening of the wear track of the measured coating, the coefficient of friction stabilized at the steady-state value attained in an uninterrupted long tribotest. This steady state value was reached at the very beginning of the test and initial instabilities in the coefficient of friction were no longer observed. It was also concluded that only after the nc-TiC/a-C:H coating gets smoothened enough within the wear track, the steady-state coefficient of friction can describe even applications where the counterpart is being periodically replaced by a new one