Effect of Nitrogen-Based Sintering Atmosphere Composition on Physical Properties of Carbon Steel Components

摘要

Nitrogen-based atmospheres are routinely used in powder metallurgy to produce a variety of simple- and complex-geometry, carbon steel components requiring close dimensional tolerances, good strength and wear resistance. These atmospheres are produced by endothermic generators, ammonia dissociators or simply by blending nitrogen and hydrogen or nitrogen, hydrogen, and an enriching gas. Because the composition of nitrogen-based atmospheres supplied by blending nitrogen and hydrogen or nitrogen, hydrogen, and an enriching gas (or natural gas) can be easily and precisely controlled, they are widely used by the powder metallurgy (P/M) industry for producing the desired carbon steel components. It is important to carefully select and control composition of the nitrogen-based atmospheres to prevent surface decarburization or carburization. For example, improper selection of hydrogen concentration in the N_2-H_2 atmospheres has been shown to result in undesirable surface decarburization and subsequent loss in surface hardness of the sintered carbon steel components8. Likewise, improper selection of the concentrations of hydrogen and natural gas in the N_2-H_2-Natural gas atmospheres can result in undesirable decarburization or carburization which affects the surface hardness and strength of sintered carbon steel components.