Cemented Carbide Sintered Waste Products And Reason Analysis

Cemented carbide is a powder metallurgy product sintered in a vacuum furnace or a hydrogen reduction furnace with cobalt, nickel, and molybdenum as the main component of tungsten carbide micron-sized powder of high-hardness refractory metal. Sintering is a very critical step in cemented carbide. The so-called sintering is to heat the powder compact to a certain temperature, keep it for a certain period of time, and then cool it down to obtain a material with the required properties. The sintering process of cemented carbide is very complicated, and it is easy to produce sintered waste if you are not careful. Today, Chuangrui Xiaobian will share with you the common sintered waste and the reasons.

1. Carbide sintered waste is the first to peel
That is to say, the surface of the cemented carbide passes through cracks on the edges, warping shells or cracks, and in severe cases, small thin skins like fish scales, burst cracks, and even pulverization. The peeling is mainly due to the contact effect of cobalt in the compact, so that the carbon-containing gas decomposes free carbon in it, resulting in a decrease in the local strength of the compact, resulting in peeling.

2. The second most common cemented carbide sintered waste is holes
Pores above 40 microns are called pores. Factors that can cause blistering may form pores. In addition, when there are impurities in the sintered body that are not wetted by the molten metal, such as large pores such as "unpressed", or the sintered body has serious solid phase and The segregation of the liquid phase may form pores.

3. The third most common cemented carbide sintered waste product is blister
There are holes in the cemented carbide alloy products, and convex curved surfaces appear on the surface of the corresponding parts. This phenomenon is called blistering. The main reason for blistering is that the sintered body has relatively concentrated gas. There are usually two kinds: one is that the air accumulates in the sintered body, and during the sintering shrinkage process, the air moves from the inside to the surface. If there are impurities of a certain size in the sintered body, such as alloy scraps, iron scraps, and cobalt scraps, the air will concentrate here. After the sintered body appears in a liquid phase and is densified, the air cannot be discharged. Blisters form on the smallest surfaces.

The second is that there is a chemical reaction that generates a large amount of gas in the sintered body. When there are some oxides in the sintered body, they are reduced after the liquid phase appears to generate gas, which will make the product bubble; WC-CO alloys are generally composed of Caused by agglomeration of oxides in the mix.

4. There is also uneven organization: mixing

5, and then there is deformation
The irregular shape change of the sintered body is called deformation. The main reasons for the deformation are as follows: the density distribution of the compacts is not uniform, because the density of the finished alloy is the same; the sintered body is severely lacking in carbon locally, because the lack of carbon reduces the liquid phase relatively; the boat loading is unreasonable; the backing plate is uneven.