Papers by Author: Juan Du

Abstract: Tungsten has the highest melting point among all metal, which makes it withstand thermal shock and erosion in high temperature environments. In this study, Tungsten coatings were sprayed onto the oxygen-free copper substrates by plasma spraying using inert gases protection. XRD, SEM and EDS were used to identify the phases, morphologies and compositions of the coatings. Vickers micro-hardness and bonding strength of the tungsten coatings were also measured. The results revealed that the hardness distribution of the tungsten coatings was different along the thickness direction. The tungsten coating without any interlayer showed higher bonding strength than that of the other two coatings with NiCrAl and W/Cu interlayers, respectively.

Abstract: A new resistance sintering method under ultra high pressure has been developed for fabrication of Mo/Cu (functional graded material) FGM. The consolidation was carried out under pressure of 8GPa, and input power of 15kW for 50s. The relative density of the FGM specimen was upwards 98% and the composition distribution was nearly the same as designed one. The micro-hardness and bend strength were measured to evaluate the sintering effects. The densification effect and microstructure of these FGM samples were investigated and the sintering mechanism was discussed.

Abstract: Tungsten coatings with different interlayers onto the oxygen-free copper substrates were fabricated by atmosphere plasma spraying. The effects of different interlayers of NiCrAl, NiAl and W/Cu on bonding strength were studied. SEM, EDS and XRD were used to investigate the photographs and compositions of these coatings. The tungsten coatings with different initial particle sizes resulted in different microstructures. Oxidation was not detected in the tungsten coating, but in the interlayer, it was found by both XRD and EDS. The tungsten coating deposited directly onto the copper substrate presented higher bonding strength than those with different interlayers.