Preparation of WC plus η Co-Reinforced Iron Matrix Composites by Plasma Remelting and Modulation of η Phase

The mismatch of hardness, thermal expansion coefficient and modulus between WC and Fe leads to large residual stresses at the WC/Fe phase boundary in WC-reinforced iron-based composites, which reduces the strength of the composites. WC + eta co-reinforced iron-based composites were prepared by in situ plasma remelting, and the eta phase content was adjusted by tuning the process sequence and C/W ratio. The microstructural changes of the composites were characterized by scanning electron microscopy and x-ray diffraction. In addition, the mechanical properties were investigated, and the strengthening mechanism was analyzed with the help of a bending tester. The physical properties of the eta phase were between those of WC and the iron matrix, relieving the residual stress within WC and the iron matrix. The material exhibited a fine-grain microstructure and high densities after hot pressing and plasma remelting. The hardness of the composites after in situ plasma remelting was 43 HRC, and the flexural strength reached 1833 MPa when C/W = 1.1. The results suggest that the strengthening mechanism of the composite is mainly load transfer and fine-grain strengthening.