High-speed steel is a type of tool steel with high hardness, high wear resistance and high heat resistance, commonly known as white steel. Its most significant characteristic - red hardness - refers to the ability of the cutting edge to resist softening when the tool is in a red-hot state during high-speed cutting, maintaining a high hardness, with HRC reaching above 60. It is mainly used to manufacture complex thin-edge and impact-resistant metal cutting tools, as well as to manufacture high-temperature bearings and cold extrusion molds, etc.
The existing φ10mm cylindrical universal high-speed steel W18Cr4V is subjected to microstructure preparation. Firstly, it is cut into small sample segments using a CT250S manual cutting machine combined with an A60 aluminum oxide cutting blade, and then directly prepared on an Alpha208 dual-control double-disc grinding and polishing machine.
The specific steps are as follows:
1. Use silicon carbide sandpaper P400 for planar grinding, and then grind in sequence at P800, P1200, and P2500.
2. Use SC polishing cloth and 3-micron diamond polishing liquid for rough polishing.
3. Use ET polishing cloth and A439 silica polishing liquid for final polishing.
After immersion in a 4% nitric acid alcohol solution, it is observed under a MN80 metallographic microscope. The metallographic structure is tempered martensite, a small amount of residual austenite, and white fine-grained secondary carbides and large-grained eutectic carbides.