Thixoforming : Semi-solid Metal Processing

Figure 8.38 Cross-sectional micrographs of the alumina films
after thermal shock experiments. The films were deposited at
560 C and at AlCl 3/O 2 ratios of (a) 1.15, (b) 0.83, (c) 0.66 and
(d) 0.5 [69].
Performance-relatedtestssuchasadhesion,high-temperaturetribologicalandthermal
shock evaluations were performed to evaluate the behaviour of coatings in a close to
real environment. The results underline that alumina thin films deposited by PECVD
are very promising candidates for die protection during semi-solid processing of steel.
8.6
Bulk Ceramic Forming Tools
8.6.1
Candidate Die Materials
8.6 Bulk Ceramic Forming Toolsj281
Ceramic materials are renowned for their outstanding high-temperature properties,
notable strength, hardness, wear and corrosion resistance, leading to their application
in a wide range of industrial processes. Owing to the high production costs of
ceramics compared with metals, these materials are typically utilized at locations
where metallic parts do not withstand the operating conditions, for example, process
temperatures above 800 C in oxidizing atmospheres and/or in contact with chemically
aggressive media or high frictional loads.