Microstructural analysis method for solidification test of chromium white cast iron by pressure casting technology

1. Sample preparation

(1) Sample grinding and polishing

Use pg-2da metallographic sample polishing machine to pre grind the sample with metallographic sandpaper, and wash the sample with water continuously during the process to keep the grinding surface free of foreign matters. After the pre grinding, the steel special polishing cloth is used for polishing until the grinding surface is smooth and no wear marks are seen.

(2) Corrosion

The corrosion of high chromium cast iron is usually caused by 4% nitric acid alcohol solution. Before corrosion, make sure that the grinding surface is clean, dry and free of foreign matters. During corrosion, immerse the sample grinding surface in the prepared nitric acid alcohol solution. With the increase of Cr content, the corrosion time is 15s and 15min respectively, and the surface color of the sample changes from bright to gray.

2. Tissue observation

The prepared samples were observed under DM200 metallographic microscope and photographed. The magnification of metallographic microscope used in this experiment is 100 times, 200 times and 500 times. After determining the field of view, image pro plus 6.0 image processing software was used to analyze the image deeply. On the eutectic spacing in the field of view( λ)、 Length diameter ratio (R1 / r2), roundness (a) and average equivalent circle diameter (d) of carbides( μ m) The number of carbides per unit area and the content of carbides per unit area were quantitatively analyzed. The metallographic structure, impact fracture and wear surface of the sample were observed by SEM with Zeiss Evo 18. EDS was used to analyze the point, line and plane composition of the target sample.

3. Phase composition analysis

Metallographic samples were used for phase composition analysis, and the carbide and matrix phases in the samples were analyzed by 45 kV and 200 Ma copper target X-ray diffraction (XRD). In XRD detection, the scanning range is 30 ~ 90 ° and the scanning speed is 2.6 ° gmin. The scanning data were analyzed by jade 6 image analysis software.