Objective To investigate the effect of self-developing investment（FUS-invest） on the reactive layer of titanium castings. Methods Three 10 mm×10 mm×1 mm pure titanium castings were founded using FUS-invest. Metallographical structure of reactive layer was observed. X-ray diffraction（XRD） and scanning electron microscope with energy-dispersive spectrum（EDS） were used to analyze the status of composition of the casting surface. Micro-Vickers hardness was measured. Results The metallograph indicated that the reactive layer was composed of coare flakeshaped α phase of grains. The value of micro-Vickers hardness with the range 243 to 314 MPa had not significantly difference under the depth of 105 μm beneath the surface. The XRD pattern clearly showed the peaks of ZrO2, SiO2, Mg2TiO4 and TiO2. EDS analysis demonstrated that the main elements were Al, Si, Zr and Cl. Conclusion FUS-invest is suited for pure titanium casting because of the thin reactive layer and less change to metallographical structure.
