The article presents the influence of mechanical alloying and plastic consolidation on the resistance to arc erosion of the composite Ag–Re material against the selected contact materials. The following composites were selected for the tests: Ag90Re10, Ag95Re5, Ag99Re1 (bulk chemical composition). Ag–Re materials were made using two methods. In the first, the materials were obtained by mixing powders, pressing, sintering, extrusion, drawing, and die forging, whereas, in the second, the process of mechanical alloying was additionally used. The widely available Ag(SnO₂)10 and AgNi10 contact materials were used as reference materials. The reference AgNi10 material was made by powder metallurgy in the process of mixing, pressing, sintering, extrusion, drawing, and die forging, while the Ag(SnO₂)10 composite was obtained by spraying AgSniBi alloy with water, and then the powder was pressed, oxidized internally, sintered, extruded into wire, and drawn and die forged. The tests of electric arc resistance were carried out for loads with direct current (DC) and alternating current (AC). For alternating current (I = 60 A, U = 230 V), 15,000 switching cycles were made, while, for constant current 50,000 (I = 10 A, U = 550 V). A positive effect of the mechanical alloying process and the addition of a small amount of rhenium (1% by mass) on the spark erosion properties of the Ag–Re contact material was found. When DC current of 10 A was used, AgRe1 composite was found to be more resistant than commonly used contact materials (AgNi10 and Ag(SnO₂)10).

Sintering Prealloyed Powders Fe-Ni-Cu-Mo Modified by Boron Base on Thermodynamic Investigations | InTechOpen, Published on: 2017-03-29. Authors: Joanna Karwan-Baczewska and Bogusław Onderka

One of the methods aimed at increasing the density in PM parts is the process of activated sintering performed by adding boron as elementary boron powder, for example. Under this researchwork novel, PM materials were obtained based on prealloyed and diffusion bonded powder (type: Distaloy SA) with the following chemical composition: Fe-1.75%Ni-1.5%Cu-0.5%Mo, with the addition of 0.55 wt.% carbon and boron (0.2, 0.4 and 0.6 wt.%). Distaloy SA samples alloyed with carbon and boron were manufactured by mixing the powders in a Turbula mixer, then compacting the mixture in a hydraulic press under a pressure of 600 MPa and sintered in a tube furnace at 1473 K for 60 minutes in a hydrogen atmosphere. The densification process of Distaloy SA parts with boron and carbon depends on the sintering mechanism. In order to evaluate the sintering mechanism of the PM samples, structural investigations using SEM/EDS were performed. During sintering of these materials at 1473 K, a liquid phase is generated as a result of the reaction occurring between the alloy matrix and the complex of carbo-borides, which leads to a considerable degree of consolidation. The elastic properties of the sintered samples (such as Young’s modulus and the damping coefficient) were measured in a tensile test with a Förster elastometer.