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1 Journal of Achievements in Materials and Manufacturing Engineering

1 2007

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Processing and properties of sinters prepared from 316L steel nanopowders

Krztoń H., Kolesnikow D., Paduch J., Molenda R.

Journal of Achievements in Materials and Manufacturing Engineering

2007

Vol. 21, nr 2

73-76

Purpose: The results of the research work on processing the sinters obtained from nanocrystalline powders of 316L steel are presented. Design/methodology/approach: The 316L steel powder has been mechanically alloyed from a set of elementary powders with use of Fritsch Vario-Planetary Mill Pulverisette 4. The time of 12 hours of milling has been needed for producing the powder. The X-ray diffraction has been used for controlling of the mechanical alloying process. The Rietveld method has been used to calculate the contents of the components of the powder. Cold and hot isostatic pressing have been applied to make the compacts. The pressure of 500 MPa and 900 MPa of cold pressing, and 150 MPa of hot pressing have been used. The green compacts have been pressed isostaticaly using liquid aluminium in the temperature of 950 degrees centigrade (1223 K). The X-ray diffraction have been used to identify the phase components of the sinters. The structure of the sinters have been observed using scanning electron microscope. The hardness values have been obtained by Vicker's test. Findings: The mechanically alloyed powder has consisted of about 94 wt.% of austenite, 5 wt.% of ferrite and not more than 1 wt.% of not alloyed molybdenum. Two kinds of sinters have been produced, one kind made of pure 316L powder, second one obtained with aluminium infiltration within the volume of the sinters. The observed porosity of the sinters has depended on the applied pressing conditions strongly, mainly on the value of cold isostatic pressure. The hardness of the first kind of sinters have achieved a value of 380 HV (98N), the hardness of the second kind - more than 400 HV (98N). Practical implications: The Al infiltrated sinter has been proposed as a material for a part of Diesel engine. As an example, a part of a fuel injection has been produced. Originality/value: The nanocrystalline 316L powder has been obtained using mechanical alloying process. The original method of hot isostatic pressing in liquid aluminium has been proposed. This method enables to produce infiltrated sinters with low porosity and high hardness values.