Powder metallurgy process

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Powder metallurgy is a way to produce metal powder and make the metal powder single or together with non-metallic powder into the production by shaping and sintering them. At the same time  the method can also obtain special material which is very difficult in ordinary smelting. In addition, it can produce a variety of a precision machine parts to save labor and materials. Despite these advantage, this method is not suitable to produce a small quantity or a small size since the  high cost of the mold and the metal powder.

Compared with the tradition material, the powder material is well-balanced which means to a well-balance organization, a stable function, a good performance in temperature process  and a  metal powder particle which is no longer limited by the element and proportion  in the alloy. This also can higher the proportion and develop a new material system. By various shaping process, the powder material can be directly made into net shaped hardware with no odds or gross hardware with little odds. And it also reduces the machine process in a large number, enhances the stock utilization and declines the cost.

 

There are variety of powder metallurgy products. First, tungsten other refractory metal alloy; Second, some hard alloys like WC, TiC, TaC which use the Co Ni as bonding agent and can be made into cutting tool and wear-resistant tool’s drill bit and hobbing. The molding can be made too. The last, Cu alloy stainless steel, Ni and some other multiholes to be used for sintering metal filter, organized rings and bearing that containing oil. With the powder smelt developing, it will be more  widely applied.

 

Fe, Cu, AL and their alloy powder are in the most common use. And the impurity and gas’S contain must be less than 1%-2%. If more, it will affect the quality. The least solid which can be separated and exists independently is called a single particle in the powder. Actually the powder is always bunching up. That is the secondary particles. The common shape of the powder is  spherical, columnar, needle-like, plate-like and sheet-like and so on, which can be measured by microscopes.

 

The total superficial area of unit weight powder can be measured by actual measurement. As well the superficial area affects the superficial characteristic like energy superficial adsorption and cohesion. The powder process function is consisted of flowing ability, filling characteristics, compressibility, formability and so on. In all the compressibility is referred to the tightness when powder is naturally in a crowd. And it is marked by the tightness and the accumulating density.

The tightness of powder relates to the powder size, shape and the surface character. The compressibility is referred to the ability how tightly the powder can be pressed. It is expressed by the pressed density in fixed unit pressure, standard molding and certain lubrication condition.

 

And it is also influenced by the plasticity or other the micro hardness. In addition the plasticity powder is better than the hard and fragile ones. So the compressibility is influenced by the shape and the structure too. The formability is referred to the ability that the pressed shape can keep the certain shape after being pressed by the smallest unit pressure. As well it can be expressed by the strength. And it is marked by the smallest unit pressure that can shape the powder. As well it can be also graded by the strength of the pressed shape.