<p>Using CaZrO₃ as the matrix, neutral and acidic binders with different powder-to-liquid ratios were added to prepare investment casting molds with various surface layers, and TA15 titanium alloy was cast. The interface microstructure of the castings was analyzed, and the interface reaction between the CaZrO₃ mold and TA15 titanium alloy with different powder-to-liquid ratios and types of binders was investigated. The results indicate that the acidic mold performs significantly better than the neutral mold, with a reaction layer thickness of about 80 μm for the neutral shell and only 60 μm for the acidic shell. The acidic binder-based shells exhibited a transition zone thickness of 218 μm, compared to 216–320 μm for neutral binder-based shells, with significantly reduced Zr and O penetration depths. To verify whether CaWO₄ is the fundamental reason for the superior performance of the acidic surface layer mold compared to the neutral surface layer mold, an acidic surface layer mold was prepared using CaWO₄, and TA15 casting was performed. The results indicate that CaWO₄ and Ca₃WO₆ are important factors contributing to the superior performance of the acidic mold compared to the neutral mold.</p>