Microstructure and Tribology of Spark Plasma Sintered Fe–Cr–B Metamorphic Alloy Powder

The spark plasma sintering (SPS) process was used to fabricate a bulk Fe–Cr–B alloy (known as Armacor M) from gas-atomized powders. The purpose of this work is to study the microstructure, hardness and tribology of this sintered bulk alloy. Post microstructure and mechanical characterizations were performed to investigate the effects of wear on the microstructure and mechanical properties. Microstructural analysis using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) showed that SPS successfully produced a fully dense bulk material containing 67 vol.% Cr_1.65Fe_0.35B_0.96 particles dispersed in 33 vol.% solid solution matrix consisting of Fe, Cr and Si. Using nanoindentation, the hardness of the Cr_1.65Fe_0.35B_0.96 particles and the matrix was found to be 24 and 6 GPa, respectively. From microindentation, the bulk hardness of the sintered alloy was 9.7 GPa (991 HV). Dry sliding wear testing under mild conditions (i.e., initial Hertzian mean contact pressure of 280 MPa) was conducted against a stainless steel pin. The steady state coefficient of friction against Armacor M was about 0.82. The wear of Armacor M proceeded primarily by adhesive and mild oxidative wear. The wear volume for Armacor M was 80% less than that of carbon steel and its wear rate was 5.53 × 10⁻⁶ mm³ N⁻¹ m⁻¹.