A metallic oxide layer of a heat-resistant element contributes to the high-temperature oxidation resistance by delaying the oxidation and has a positive effect on the increase in electrical resistivity. In this study, green compacts of Fecralloy powder mixed with amorphous and crystalline silica are oxidized at 950°C for up to 210 h in order to evaluate the effect of metal oxide on the oxidation and electrical resistivity. The weight change ratio increases as per a parabolic law, and the increase is larger than that observed for Fecralloy owing to the formation of Fe-Si, Fe-Cr composite oxide, and Al₂O₃ upon the addition of Si oxide. Si oxides promote the formation of Al₂O₃ and Cr oxide at the grain boundary, and obstruct neck formation and the growth of Fecralloy particles to ensure stable electrical resistivity.

A lean alloy is defined as a low alloy steel with a minimum amount of the alloying element that maintains the characteristics of the sintered alloy. It is well known that the addition of elements such as Cr, P, Si, or Mn improves the mechanical characteristics of the alloy, but decreases the sinterability. The mother alloy is used to avoid an oxidation reaction with the alloying elements of Cr, P, Si or Mn. The purpose of this study is to determine the change in the mechanical properties of Fe-P-Mo and Fe-P-Mn alloys as a result of the addition of Si. In this article, the Fe-P-Mo and Fe-P-Mn alloys to which Si is added are compacted at 7.0 g/cm³ and then sintered in H₂-N₂ at 1120°C. The P around the macropores and large grains reduces due to the formation of SiO₂ as the Si content increases. This is caused by the increase in strength owing to reducing intergranular fracture by suppressing the reaction with oxygen.

Citations

Citations to this article as recorded by  

• The Effects of Si or Sn on the Sintered Properties of Fe-(Mo,Mn)-P Lean alloy
  Woo-Young Jung, Jin-Uk Ok, Dong-Kyu Park, In-Shup Ahn
  Journal of Korean Powder Metallurgy Institute.2018; 25(4): 302.     CrossRef
• Sintering behavior of Fe-(Mo-Mn-P)-xSi alloys according to the Green Density
  Woo-Young Jung, Jin-Uk Ok, Dong-Kyu Park, In-Shup Ahn
  Journal of Korean Powder Metallurgy Institute.2017; 24(5): 400.     CrossRef

In order to improve the high-temperature oxidation stability, sintered 434L stainless steel is studied, focusing on the effect of the addition of metallic oxides to form stable oxide films on the inner particle surface. The green compacts of Fecralloy powder or amorphous silica are added on STS434L and oxidized at 950°C up to 210 h. The weight change ratio of 434L with amorphous silica is higher than that of 434L mixed with Fecralloy, and the weight increase follows a parabolic law, which implies that the oxide film grows according to oxide diffusion through the densely formed oxide film. In the case of 434L mixed with Fecralloy, the elements in the matrix diffuse through the grain boundaries and form Al₂O₃ and Fe-Cr oxides. Stable high temperature corrosion resistance and electrical resistivity are obtained for STS434L mixed with Fecralloy.