A high-velocity oxyfuel plant was converted to process aluminum oxide. Burner nozzles with different geometries were evaluated for use based on experimental measurements and numeric simulations. Although the modified nozzles promised an improvement in the melting of alumina particles, it was found that some of the melted alumina caked on the inside of the nozzle and fused together into large particles that eventually dislodged, causing a reduction in transfer efficiency. This paper explains how the caking problem was solved by combining the output of a high-velocity oxyfuel gun with that of a combustion flame spraying gun. Tests show that the hybrid solution produces hard alumina coatings with relatively dense microstructure at a transfer efficiency greater than 50%. Paper includes a German-language abstract.

This work investigates the influence of powder characteristics on thermal spray coatings produced from titanium suboxide powders. The powders used were prepared from commercially fused and ground titanium dioxide reduced in a mixture of hydrogen and argon gas. Two particle sizes were produced and subsequently applied by atmospheric plasma and HVOF spraying. Originally melted and crushed powder fractions served as a reference. All deposits showed high wear resistance, particularly the HVOF-sprayed layers. Paper includes a German-language abstract.

This paper examines the effect of spraying conditions and WC grain size on the wear behavior of WC-Co coatings. Two powders, one with a fine grain fraction and one with a more conventional grain fraction, were applied using liquid and gas HVOF systems. All coatings were subjected to sliding wear tests against an aluminum oxide ball. A sintered WC-Co composite was also tested for comparison. The sintered composite structure (cermet) exhibited the highest wear resistance, while the conventional powder sprayed by means of a gas-operated burner produced the best coating. Paper includes a German-language abstract.

A number of studies have examined the influence of process parameters on the microstructure and corrosion resistance of metallic coatings produced by gas-fuel HVOF spraying, but much less is known about the coatings produced by liquid-fuel HVOF processes. The aim of this study is to investigate the corrosion behavior and microstructure of nickel and cobalt alloys deposited by both methods and show how it compares with that of various superalloys. Paper includes a German-language abstract.

This paper reports on a modified diamond jet HVOF spray gun, which makes it possible to produce layers of stainless steel and nickel alloys with very low levels of oxide and porosity. The corrosion behavior of these layers is compared with that of coatings produced with a conventional HVOF gun. Cross-sectional examinations carried out before and after corrosion testing show where and when corrosion attacks occur. Paper includes a German-language abstract.