Yifu Shen

Effects of processing parameters on direct laser sintering of multicomponent Cu based metal powder

Abstract Direct laser sintering of a multicomponent Cu based metal powder was successfully processed through the mechanism of liquid phase sintering with partial melting of the powder. The effects of processing parameters such as laser power, scan speed, scan line spacing and layer thickness on the densification and microstructural evolution of the laser sintered powder were investigated. It was found that with increasing laser power or decreasing scan speed, the density of the sintered parts increased and the microstructures became denser. However, the combination of higher laser powers (>400 W) and higher scan speeds (≥0·06 ms−1) gave rise to balling effect. A successive transition from discontinuous scan tracks to coherently joined ones occurs with decreasing scan line spacing. Lowering the thickness of the powder layer promises an improvement in bonding coherence between sintered layers. A single factor termed energy density by volume is defined to evaluate the combined effect of various processing parameters on the density of laser sintered powder. With increasing the energy density by volume up to ∼0·16 kJ mm−3, the densification rate is relatively high. However, with intensifying the energy density over ∼0·23 kJ mm−3, the mechanism of particle bonding may change into full melting/solidification, leading to a decrease in the sintered density.

Selective laser melting of in situ TiN–Ti5Si3 composites with RE–Si–Fe addition: comparative study

Abstract A comparative study was conducted to investigate the influence of rare earth (RE)–Si–Fe addition on the microstructures and tribological properties of in situ TiN–Ti5Si3 composites prepared by selective laser melting (SLM). With the addition of 3 wt-% RE–Si–Fe, the shape of in situ TiN reinforcing particles became rounded and smoothened, the particle size was refined and the dispersion state was homogenised. Relative to TiN–Ti5Si3 composites without RE addition, the average friction coefficient of SLM processed RE containing composites decreased from 0·85 to 0·55, and the resultant wear rate decreased from 3·79×10−4 to 2·65×10−4 mm3 N−1m−1. Metallurgical functions of the RE elements in improving the SLM processability and the resultant wear performance of in situ composites were elucidated.