Thixoforming : Semi-solid Metal Processing

Figure 3.47 High-solution scanning electron microscope image
of a deeply etched specimen, annealed at 595 C for 30 min,
which shows acicular pearlite.
only observable at high magnifications. SEM images show that the lamellae exhibit a
thickness of up to 20 nm (Figure 3.47).
Examinations concerning the wear characteristics of steel X210CrW12 were
executed by means of rubber wheel abrasion tests. The condition of a conventional
standard heat treatment (970 C/30 min/oil þ 300 C/2 h) was compared with the
condition of a formerly partial liquid X210CrW12 (1270 C/30 min) and subsequently
aged at 490 and 595 C to its maximum hardness. The determined volume loss
reveals excellent wear resistance, in comparison with literature values of nitrided
steels (Table 3.8). In the annealed state, the formerly partial liquid material contain
retained austenite contents, as already established in the literature concerning extraordinary
wear characteristics. Examinations of high-chromium content cast iron
Table 3.8 Hardness values (HV10) and volume loss during the
wear experiments (dV) of the conventionally hardened and the
thixo-heat-treated steel X210CrW12 in comparison with wearresistant,
nitrided chromium steels.
970 C
30 min
and
300 C
2h
X210CrW12 Cr-alloyed tool steels
Quenched
1270 C/20 min
and subsequently
595 C
40 min
3.6 Microstructure Analysis and Material Propertiesj95
490 C
120 min
Hardness
(HV10)
722 370 719 784 490 545 615 745 800 940
dV (mm 3 ) 4.2 10 3.6 3.8 13.3 9.9 8.0 11.8 3.3 2.1