Laser melt injection of monocrystalline WC particles into Ti-6AL-4V

Abstract

The laser melt injection (LMI) process was used to produce WC particles (WCp) reinforced Ti-6Al-4V metal matrix composites (MMCs). In particular monocrystalline WCp were used as injection particles to avoid the intercrystalline cracking often observed in granular or cast WCp reinforced MMCs. WCp were injected into the extended part of the melt pool just behind the laser beam to prevent WCp from excessive dissolution. Moreover, different parameters were applied, and the processing window of LMI was obtained. The produced MMCs layers were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A graded distribution of WCp along the depth direction of the MMCs layer is observed. In addition, some new phases such as TiC and W2C can be found in the MMCs layer. TiC decreases both in quantity and size with the distance from the surface to the bottom of the MMCs layer, and a graded microstructure of TiC in the matrix is also achieved. Two types of reaction layers around WCp are observed, namely an irregular reaction layer and a cellular reaction layer. The composition of the neighbouring melt pool plays a critical role in the growth and subsequent morphology of reaction layers around WCp.The laser melt injection (LMI) process was used to produce WC particles (WCp) reinforced Ti-6Al-4V metal matrix composites (MMCs). In particular monocrystalline WCp were used as injection particles to avoid the intercrystalline cracking often observed in granular or cast WCp reinforced MMCs. WCp were injected into the extended part of the melt pool just behind the laser beam to prevent WCp from excessive dissolution. Moreover, different parameters were applied, and the processing window of LMI was obtained. The produced MMCs layers were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A graded distribution of WCp along the depth direction of the MMCs layer is observed. In addition, some new phases such as TiC and W2C can be found in the MMCs layer. TiC decreases both in quantity and size with the distance from the surface to the bottom of the MMCs layer, and a graded microstructure of TiC in the matrix is also achieved. Two types of reaction layers around WCp are observed, namely...