Analysis of difficulties in powder metallurgy processing

Analysis of difficulties in powder metallurgy processing

With the continuous development of industry, powder metallurgy has gradually entered the public's vision in the automotive industry, daily necessities, mechanical equipment and other fields, and has occupied a certain importance. However, there are still many friends who do not know much about powder metallurgy materials. What are the processing difficulties of powder metallurgy materials?

powder metallurgy

Powder metallurgy materials have unique chemical composition, physical and mechanical properties that cannot be obtained by traditional melting and casting processes. For example, the porosity of the materials can be controlled, the material structure is uniform, and there is no macro segregation (after solidification of the alloy, there is no non-uniform chemical composition on different parts of its section due to the macro flow of liquid alloy), which can be molded at one time. Generally speaking, powder metallurgy materials are porous, semi dense or fully dense materials (including products) made by powder metallurgy process.

(1) Porosity leads to micro wear of tool edge. When machining powder metallurgy materials with a tool, when the tool moves back and forth from the hole to the solid particles, the tool tip is continuously impacted, which will result in small cracks on the cutting edge, which will increase until the edge breaks.

(2) Porosity reduces the thermal conductivity of powder metallurgy parts. The temperature of the cutting edge is very high when the tool is cutting, which will cause the wear and deformation of the crescent crater of the tool.

(3) The porous structure will increase the surface area and cause oxidation or carbonization during heat treatment. These oxides and carbides are very wear-resistant, affecting the machinability of powder metallurgy materials.

(4) Due to the existence of voids, the hardness value of powder metallurgy materials also fluctuates in a small area. For example, even if the measured macro hardness is HRC20~35, the particle hardness of components may be higher than HRC60, which will lead to severe and rapid edge wear.

(5) Many P/M parts can be heat treated. After heat treatment, the hardness and strength will become higher. After sintering and heat treatment, the surface will also contain hard and wear-resistant oxides and carbides.

(6) Inclusions may also exist in powder metallurgy materials. During processing, these inclusion particles will rub in front of the tool, forming scratches or scratches on the part surface, and also causing tool wear.