Are Large Particles of Iron Detrimental to Properties of Powder Metallurgy Steels?

Abstract

It is experimentally shown that a removal of particles exceeding 100 microns in size from iron powders typically used in the fabrication of medium density powder metallurgy steels has a weak effect on apparent density, flowability and compressibility of blends as well as on density and strength of green bodies. An elimination of such particles, i.e., cutting off a heavy tail of a size distribution histogram at the 100 μm threshold, improves a compositional uniformity of sintered materials, but has no noticeable beneficial effect upon the strength of a final product, which is likely be determined by a fraction of pores and their shapes. A presence of soft pearlitic inclusions hardly matters unless their number density becomes so large that a 3D continuity (integrity) of a hard martensitic matrix is lost. This finding suggests that such an expensive preparatory step as sieving away large particles from as-received mixtures would bear no technological advantages. It was experimentally found that an attempt to lower the threshold below 100 μm noticeably worsened apparent density, flowability and compressibility.

Effect of pore structure on the impact toughness of copper-infiltrated sintered steel

“…Limited research exists on the influence of the pore structure of the sintered steel skeleton on the copper infiltration process. Nevertheless, it has been demonstrated that the pore structure plays a crucial role in the permeability of liquids and the mechanical properties of the infiltrated materials [16][17][18][19][20][21][22][23][24]. For example, Johannes et al [22] experimented by modifying the proportion of fine powder added to the initial powder of H11 tool steel within the range of 0 wt% to 15 wt%.…”

One-Step Enameling and Sintering of Low-Carbon Steels

“…PM is a technology applied to many metals, such as steel [28][29][30][31], stainless steel [32][33][34], aluminium [35,36], copper [37], titanium [38][39][40][41], and magnesium [42,43], etc. Metal powders can be pre-alloyed [44,45] or mechanically alloyed [34,46]; it depends on the application sought.…”