The sintering atmosphere of powder metallurgy is an important factor affecting the properties of sintered products

Metal powder metallurgy is a kind of technology that USES metal powder as raw material, through molding and sintering to make metal or alloy parts. MIM industry leaders use this technology to directly produce porous, semi-dense or fully dense materials and products, so it is widely used.

In sintering of metal powder metallurgy products, sintering atmosphere is one of the important factors affecting the properties of sintered products. The sintering atmosphere of metal powder metallurgy can be divided into three types: protective atmosphere, controllable atmosphere and air atmosphere. The following is the relevant content of the three sintering atmospheres summarized by dahong new materials in their MIM technology experience.

I. protect the atmosphere

Protective atmosphere is divided into reducing atmosphere and neutral atmosphere, reducing atmosphere is divided into hydrogen and decomposition of ammonia. In the sintering process, the main function of protective atmosphere is to protect the sintered products from oxidation.

Reducing atmosphere: hydrogen has a strong permeability under certain temperature conditions, is a kind of flammable gas with strong chemical activity, often in tungsten alloy, hard alloy, stainless steel and other refractory powder metallurgy products sintering as a protective atmosphere; Decomposition of ammonia liquid ammonia is obtained after thermal decomposition by the combination of hydrogen and nitrogen mixture gas, can be in powder metallurgy as a reducing agent, also used as a sintering atmosphere, MIM experts found except for some products containing nitrogen composition with the atmosphere produces chemical reaction can't use this sintering atmosphere, most of the metal can use this to sintering atmosphere.

Neutral atmosphere: neutral atmosphere mainly includes nitrogen, ammonia and vacuum, which is widely used in the precision and complex parts. Vacuum sintering can avoid the harmful components in the atmosphere causing pollution and other adverse effects on small complex metal parts.

Ii. Controllable atmosphere

Guangdong MIM experts divided this kind of atmosphere into exothermic and endothermic atmosphere, are converted from hydrocarbons.

The exothermic type can be used to control the carbon content in the sintered products of powder metallurgy. The carbon potential of weak exothermic atmosphere is very low, which can only be used for non-oxidation heating when sintering low carbon steel and copper products: the carbon potential of strong exothermic atmosphere is higher, which can be used to prevent the oxidation of iron and copper based parts in powder metallurgy and reduce the decarbonization of iron based parts.

Compared with exothermic atmosphere, endothermic atmosphere is a controllable atmosphere with stronger reducing ability and higher carbon potential. In powder metallurgy, it is mainly used as a protective atmosphere in sintering iron based parts and copper based parts, and sometimes used as a carburizing agent.

Iii, air atmosphere

This sintering atmosphere is mainly through certain air and gas in the sintering furnace, which can also be regarded as sintering under normal pressure. Dahong new materials are generally applied in sintered products of small complex metal parts and MIM ceramic materials.