EFFECT OF NITROGEN ON MECHANICAL PROPERTIES OF SINTERED 409L STAINLESS STEEL

摘要

Sintering of ferritic stainless steels is necessary to be carried out in a proper atmosphere. Normal atmosphere, namely cracked ammonia containing 75%H_2 and 25%N_2, employed for sintering of iron and steels, causes detrimental effect on properties of sintered ferritic stainless steels. The sintered alloys significantly lose their elongation. Nitrogen in the atmosphere is the main cause of embrittlement. Sintering of these alloys in pure hydrogen is the perfect way to prevent nitride formation. However, the cost of sintering is expensive so it causes less competitiveness of the sintered ferritic stainless steels in the P/M markets. Mixed H_2 + N_2 atmosphere with suitable content would reduce sintering cost while keep desirable properties of the sintered products. It was found that the sintered 409L stainless steel exhibited good elongation (about 15%) and increased strength and hardness when the 80%H_2 + 20%N_2 atmosphere was employed. Better strength and hardness were attributed to hardening effect caused by nitrogen.