What do you imagine when someone asks what cemented carbides is?
You may say, "What is it? I don't know exactly. It sounds very hard. Is it harder han diamond?" What kinds of hard material do you know in our environment? You may think of glass, sapphire, stone, iron and diamond. What is the order of hardness among them? In your elementary or junior high school days, you might try to rub two stones each other and study that one got hurt is the softer. The hardness determined by that method is Moh's hardness. Table 1 shows an example of the hardness. The table also shows other indexes for hardness.
In the table, cemented carbide is classified as degree 9, showing that it is harder than almost all minerals such as sapphire. Among natural minerals, diamond is only harder than cemented carbide, and those in artificial minerals harder than cemented carbide are very few like silicon carbide and boron carbide. Therefore, cemented carbide is not the hardest material. Why is it called "ultra hard" alloy ? That is because it is the hardest in metals.