To examine the metallographic microstructure, the sample was firstly ground in 600-, 1200-, and
2000-grid waterproof silicon carbide paper and polished in wool felt, then it was etched in FeCl3 for a
few seconds. The microstructure was examined in an optical microscope, as shown in Figure1.
Material hardness was tested by the Vickers hardness tester (Wilson Hardness TUKON
TM
2500).
The cylindrical sample was used in the test. Dimension of the sample was 20mm in height and
18.5mm in diameter. Nine points along the radial direction in the end surface of the sample were
measured. The load was 0.1 kilogram and the loading time was 10 seconds.