Microstructure and mechanical properties of diffusion alloyed steel composites reinforced by ceramic particles

The ceramic particle reinforced Fe‒0.5Mo‒1.75Ni‒1.5Cu‒0.7C diffusion alloyed steel composites were prepared by the conventional powder metallurgy techniques, using SiC, TiC, and TiB₂ as the reinforced ceramic particles, respectively. The microstructures of the sintered specimens were observed by the optical microscope and scanning electron microscope, and the hardness, tensile strength, and friction-wear performance were tested systematically. In the results, the interface bonding between the matrix and the ceramic particles is perfect due to the excellent chemical compatibility of SiC and TiB₂ with the matrix; the interface bonding between the matrix and TiC particles is inferior because of the high chemical stability. The relative density of the sintered specimens reinforced by SiC and TiC decreases monotonously with the increase of the ceramic phase mass fraction; while the relative density of the sintered specimens reinforced by TiB₂ increases firstly and then decreases with the increase of TiB₂ mass fraction, and the relative density reaches the maximum value when the TiB₂ mass fraction is 0.9%. The hardness of the sintered specimens reinforced by SiC and TiB₂ increases monotonously with the increase of the ceramic phase mass fraction, and the increased rate becomes gently when the ceramic particle mass fraction exceeds 1.2%; the hardness of the sintered specimens reinforced by TiC increases firstly and then decreases with the increase of TiC mass fraction and reaches the maximum value when the TiC mass fraction is 0.9%. The tensile strength of the sintered specimens reinforced by SiC and TiC decreases monotonously with the increase of the ceramic particle mass fraction, a small amount of SiC addition has no visible impairment on the tensile strength; the tensile strength of the sintered specimens reinforced by TiB₂ increases firstly and then decreases and reaches the maximum value of 971.7 MPa when the TiB₂ mass fraction is 0.6%, which increases by over 14.1% compared with the martrix. The positive effect of the ceramic particles on the performance of the sintered specimens is TiB₂, SiC, TiC in turn.