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1 Journal of Achievements in Materials and Manufacturing Engineering

1 2008

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Modification of Cr-Mo low alloyed steels by addition of Mn via mechanical milling

Sicre-Artalejo J., Campos M., Torralba J. M.

Journal of Achievements in Materials and Manufacturing Engineering

2008

Vol. 28, nr 2

199-202

Purpose: The PM industry is in continuous development due to the necessity to increase its potential and competitiveness. This fact and the demand for substituting certain alloying elements used so far, require the addition of new alloying elements and new processes leading to and optimization of costs, strength and tolerances. A different method for introducing Mn into the alloying system is proposed in the present work. Mechanically-blending and mechanically alloying Mn containing master alloys are generated and based on three different steels grades, ASC100.29 (plain iron), Astaloy CrL and Astaloy Mo (pre-alloyed systems). Design/methodology/approach: To profit Mn sublimation effects, small Mn particles, in order to increase the specific surface available to sublimate, must be homogenously added. Different milling times are considered in order to attain the desired master alloys containing 50% of Mn which is diluted in each base powder by normal mixing. New alloying systems were then pressed to a green density of 7.1 g/cm3 and sintered at 1120 ° C in 90N2-10H2 atmosphere. STA showed Mn diffusion during sintering and a densification enhancement. Findings: The sublimation of Mn during sintering provides some specific phenomena which facilitate the sintering of alloying elements with high oxygen affinity. The resulting mechanical properties and the microstructures must be discussed considering the high energy stored in the master alloy which favours the mass transport mechanism during sintering. Research limitations/implications: Research is being continued with the optimisation of the mechanical properties and the application of heat treatments taking the profit of the increase of the hardenability induced by Mn. Originality/value: Mn seems a viable substitute for alloy elements used so far in PM, such as Ni and Mo. Following European regulations Ni cannot be used in its elemental powder form because of its effects on health and Mo has increased its price in the last years.