Low-temperature sintering and hot rolling of hard powder magnetic Fe-Cr-Co alloy

Abstract

In the present work, a method for processing of a technically usable Fe-26 %Cr-16 %Co-2 %Mo-2 %W hard magnetic alloy from powder raw materials is proposed. The distinctive feature of the method is the lowered sintering temperature of powder compacts (1100-1200°C). Sintered blanks are subjected to a hot rolling process at 1150°С. The magnetic material produced by the proposed method has a relative density of about 97 to 98 %. Magnetic properties of the alloy sintered at 1200°C (B r = 1,2 T, H cb = 51kA / m, (BH) max = 30 kJ / m 3) are on the same level as for alloys obtained by powder metallurgy methods with sintering temperatures higher than 1300°C and their cast analogs. At the same time, low magnetic properties were obtained on the alloy sintered at 1100°C with the following hot rolling. Using EDX analysis and X-ray phase analysis it has been established that this is due to the presence of a significant fraction of non-magnetic γ-phase in the samples. Apparently, under these sintering conditions the redistribution of alloy components does not succeed. Tensile strength tests of the hot-rolled alloy after heat treatment showed a significant effect of sintering temperature on the samples strength. The tensile strength was higher for the samples sintered at 1100°C (700-930 MPa) as compared to the samples sintered at 1200°C (520-590 MPa). Microstructural studies of the samples showed that alloy sintered at 1200°C had a more coarse-grained structure. Apparently, this is a cause of the tensile strength reduction.

Influence of Energy-Mechanical Treatment on Structure-Mechanical Properties of Co–Cr–Mo Alloys Obtained by Spark Plasma Sintering

“…We performed the spark plasma sintering of the samples under the equal conditions at a LABOX-650 (Japan) installation: in vacuum, at the temperature of 1000°C, under the pulse current power of 500-2500 A; the heating rate was 50°C/min, the pressure was 50 MPa, and the holding time at 1000°C was 5 min. We selected the sintering temperature on the basis of the analysis of the data [2,26,28]. Each load contained 23 g of the powder burden.…”

“…structure of the obtained sintered products, resulting in a deterioration of their mechanical properties [2,10,13,14].…”

“…For example, such alloys are often used to create gas turbine nozzles and rotor blades, to manufacture biomedical implants, as anti-corrosion and wear-resistant materials, etc. [1][2][3][4][5][6][7][8][9]. Recently, certain (Co-Cr-Mo) alloys are often used for additive technologies, in particular, for 3D printing when creating products of intricate shape and for texturing the surface of components [5,6].…”

“…Currently, the powder metallurgy methods are of high priority for manufacturing products of special purpose, including products made of alloys based on Co, Cr, and Mo with high structure-mechanical properties [2,[10][11][12].…”