INFLUENCE OF HIGH ENERGY VIBRAMILLING ON THE ANNEALED AND SINTERED STRUCTURES AND PROPERTIES OF AN IRON-27 NICKEL-16 CHROMIUM AUSTENITIC POWDER METALLURGY STEEL.

摘要

P/M alloy steel compacts are commonly prepared from prealloyed and premixed elemental powder. The particles of prealloyed powder all have the same composition, thus assuring homogeneity throughout P/M processing. Alloys prepared from blended elemental powders depend on diffusional transport during sintering to achieve homogeneity. Depending on powder characteristics, the interdiffusion distances can be quite large, thereby requiring longer sintering times and/or higher temperatures to achieve a desired degree of homogeneity.;High energy vibratory ball milling is used to intermix the alloying constituents, iron, nickel, and chromium, to produce a blended powder consisting of individual particles having a striated microstructure of alternate layers of iron, nickel, and chromium. Sintering and homogenization are enhanced by the short diffusion paths, the intimacy of contact between iron, nickel, and chromium, and release of stored energy in the powder. This study describes the effect of high energy vibratory ball milling on the alloy powder characteristics and properties, the density, microstructure, pressing, and sintering characteristics of the milled and annealed powders, and the mechanical properties of the sintered alloy.