Search

Workability and early-ages mechanical properties are important indicators of magnesium potassium phosphate cement (MKPC) as a repair material. The effect of metakaolin (MK) on the setting time, fluidity and early-ages strength of MKPC paste was studied, and its influence mechanism was analyzed through pore structure, microstructure and nanomechanical properties. The results show that 10% and 20% of MK prolong the setting time of MKPC paste, but excessive MK shortens the setting time of MKPC paste. Meanwhile, incorporating MK reduces the fluidity of MKPC paste, and the early-ages strength of MKPC specimens increases when the substitution ratio of MK is 10%. When 10% of MK is incorporated to the MKPC paste, the 30-d shrinkage of the sample is only 69% of the control group. Meanwhile, a proper amount of MK can improve the pore structure of the MKPC specimen and make its microstructure denser by generating amorphous aluminosilicate phosphate gel. It is observed from the nano-scale characteristics that incorporating 10% MK can reduce the content of pore phase and unreacted MgO phase, and increase the volume fraction of hydration products. [ABSTRACT FROM AUTHOR]

In this study, a novel hybrid ultrasonic-electromagnetic (UEM) field was introduced into laser cladding (LC) to fabricate Inconel 718/60% tungsten carbide (WC) metal matrix composites (MMCs) coating on Inconel 718 substrate. Effects of hybrid UEM field on macrostructural, microstructure, phase composition, crack propagation and microhardness of MMCs coating were studied. Results show that under hybrid UEM field, the height of the MMCs coating increases, the cracks in MMCs coating can be effectively eliminated, the distribution of WC particles in the coating becomes more homogeneously, and the heat damage degree of WC particles is significantly decreased. Moreover, hybrid UEM field helps refine the microstructure and promote the transition of coarse carbide precipitates to the smaller spherical carbides. As a result, the microhardness of MMCs coating distributes more evenly in the coating under hybrid UEM field. [ABSTRACT FROM AUTHOR]