Effect of Cr Contents on the Porosity Percentage, Microstructure, and Mechanical Properties of Steel Foams Manufactured by Powder Metallurgy

Abstract

In this work, the effect of Cr content (0, 1, 2, 3, and 4 wt%) on the porosity percentage, cell walls microstructure, and mechanical behavior of the steel foams containing 0.6 wt% C, 1.5 wt% Cu, and 2 wt% P manufactured by powder metallurgy using leachable space holder technique was investigated. The microstructure of the cell walls was evaluated by optical microscopy (OM) and scanning electron microscopy (SEM). The mechanical behavior of the manufactured foams was studied by compression and hardness tests. The porosity values of the steel foams were between 72 and 76%, and increase in Cr content (from 0 to 4 wt%) did not have significant effect on the porosity. The results revealed that the microstructure of cell walls comprised of copper islands, intergranular carbides, phosphorus phases, and pearlite. The liquid phase sintering (LPS), solution strengthening by Cr, and the formation of intergranular carbides lead to improve the mechanical behavior of steel foams. The elastic region, long sawtooth plateau region, and fracture point are manifestly observed in the compressional stress versus strain curves. By increasing the Cr content, the plateau stress (from 41.7 to 153.2 MPa), the fracture point stress (from 42.3 to 182.4 MPa), and the elasticity modulus (from 1.23 to 3.73 GPa) increase.