TY - THES

T1 - Synthesis of alpha-(Al,Cr)2O3 solid solution coatings with different Al/(Al+Cr) ratios by pulsed DC magnetron sputtering

AU - Tkadletz, Michael

N1 - embargoed until 18-11-2016

PY - 2011

Y1 - 2011

N2 - The aim of the present work was to sputter deposit solid solutions of alpha-(Al,Cr)2O3 coatings with different Al/(Al+Cr) ratios on cemented carbide substrates and compare them with respect to their crystallographic structure, residual stresses and mechanical as well as tribological properties. Since the sputter deposition of pure alpha-Al2O3 coatings in industrial scale is not possible yet, Cr2O3 is added to form a hexagonal phase which is isostructural with alpha-Al2O3. An industrial scale sputtering plant was equipped with segmented Cr/Al targets on one side of the recipient. On the other side, two TiAl targets were mounted to deposit a TiAlN base layer in order to improve the film adhesion. Due to the special geometry of the segmented targets, coatings with Al contents from 22 to 49 at% could be deposited. X-ray diffraction investigations showed that a hexagonal solid solution of alpha-(Al,Cr)2O3 was obtained over the whole range of chemical compositions. The determined lattice constants were in good agreement with the lattice constants calculated according to Vegard´s law. The hardness of the deposited films was in the range of 17-28 GPa and depended strongly on the determined compressive stresses. The coefficient of friction showed no significant trend in relation to the Al content at room temperature. At 500 as well as at 700 °C, an increasing coefficient of friction with increasing Al content was obtained. At 500 °C the average coefficients of friction were slightly higher than the values measured at room temperature and at 700 °C. In conclusion, well crystalline solid solutions of (Al,Cr)2O3 in alpha-modification with different Al/(Al+Cr) ratios using an industrial scale sputtering plant have been successfully deposited. The deposited coatings show a huge potential for wear protective applications like coatings for cutting tools.

AB - The aim of the present work was to sputter deposit solid solutions of alpha-(Al,Cr)2O3 coatings with different Al/(Al+Cr) ratios on cemented carbide substrates and compare them with respect to their crystallographic structure, residual stresses and mechanical as well as tribological properties. Since the sputter deposition of pure alpha-Al2O3 coatings in industrial scale is not possible yet, Cr2O3 is added to form a hexagonal phase which is isostructural with alpha-Al2O3. An industrial scale sputtering plant was equipped with segmented Cr/Al targets on one side of the recipient. On the other side, two TiAl targets were mounted to deposit a TiAlN base layer in order to improve the film adhesion. Due to the special geometry of the segmented targets, coatings with Al contents from 22 to 49 at% could be deposited. X-ray diffraction investigations showed that a hexagonal solid solution of alpha-(Al,Cr)2O3 was obtained over the whole range of chemical compositions. The determined lattice constants were in good agreement with the lattice constants calculated according to Vegard´s law. The hardness of the deposited films was in the range of 17-28 GPa and depended strongly on the determined compressive stresses. The coefficient of friction showed no significant trend in relation to the Al content at room temperature. At 500 as well as at 700 °C, an increasing coefficient of friction with increasing Al content was obtained. At 500 °C the average coefficients of friction were slightly higher than the values measured at room temperature and at 700 °C. In conclusion, well crystalline solid solutions of (Al,Cr)2O3 in alpha-modification with different Al/(Al+Cr) ratios using an industrial scale sputtering plant have been successfully deposited. The deposited coatings show a huge potential for wear protective applications like coatings for cutting tools.

KW - Alumina

KW - aluminum oxide

KW - Al2O3

KW - (Al

KW - Cr)2O3

KW - pulsed magnetron sputtering

KW - PVD

KW - Aluminiumoxid

KW - Al2O3

KW - (Al

KW - Cr)2O3

KW - pulsed magnetron sputtering

KW - PVD

M3 - Diploma Thesis

ER -