Method for the determination of parameters in the sintering process of mixtures of the elemental powders Fe-Cr and Fe-Cr-Ni

Tárique Hernandez Schneider,Luciano Volcanoglo Biehl,Ederson Bitencourt Das Neves,Jorge Luiz Braz Medeiros,José De Souza,Fábio Augusto Dornelles Do Amaral

doi:10.1016/j.mex.2019.08.009

Abstract

The achievement of varied metal alloys through the sintering of mixtures of elemental metallic powders can provide great flexibility of production of these alloys. The possibilities of controlling the composition and the resulting properties of the alloy are of great importance for metallurgy. Otherwise the alloys involving chromium offer many difficulties for their attainment through the process of powder metallurgy (PM). In the formation of alloys with chromium (Cr), an oxide layer that prevents the ideal contact between the particles is formed. Hence the need for researches that study sintering processes and that can solve this difficulty. With this objective, this paper presents a method to determine parameters and describe the sintering process of mixtures of the elemental metallic powders Fe-Cr and Fe-Cr-Ni, assessing the elements’ diffusing capacity and the possible alternative composition of an alloy. The method used Scanning Electron Microscopy (SEM) associated with Energy Dispersive Spectrometry (EDS), X-ray diffraction (XRD) and Vickers microindentation hardness analysis (HV). For the microstructural characterization, we used optical microscopy (OM) and SEM. And EDS mapping was applied for the analysis of the elements’ dispersion.•The method makes it possible to define the ideal sintering time to obtain a good diffusion of the mixtures of the metallic powders Fe-Cr.•With the method, it is possible to verify the dispersion of the powders and whether the microstructure generated is similar to the ones of prealloyed powders.•With the applied procedures, the conditions for the formation of Fe-Cr alloys can be obtained by mixing dissociated and diffusion-bonded elemental metallic powders.

Highlights

It is possible to verify the dispersion of the powders and whether the microstructure generated is similar to the ones of prealloyed powders
An X-ray diffraction analysis is executed for the complementary characterization of the composition
A press with capacity for 30 tonnes or more, duly calibrated, should be used. This procedure follows the recommendations of the norm ASTM B925-15 section 7, which identifies the procedure for the making of powder metallurgy (PM) samples, namely: (a) the lower punch, smaller, is inserted into the die, supported by the elastic spacer; (b) the powder is inserted into the cavity, the upper punch; (c) the assembly is positioned in the press and a load of 1 t is applied to support the die and remove the spacer; (d) the load is applied to its final value at a rate of approximately 20 MPa/second, not exceeding 10 s of permanence; and (e) the pressure is withdrawn, the lower punch is removed and an upper spacer is positioned for the extraction of the compact, executed in the same equipment [1]

Summary

Introduction

The method makes it possible to define the ideal sintering time to obtain a good diffusion of the mixtures of the metallic powders Fe-Cr. With the method, it is possible to verify the dispersion of the powders and whether the microstructure generated is similar to the ones of prealloyed powders.

Results

Conclusion