Microstructures and tensile properties of TiC/GH5188 composites manufactured by laser melting deposition

To improve the high-temperature performance of GH5188 cobalt-based superalloy， 10%（volume fraction） TiC particle-reinforced GH5188 composites are fabricated by laser melting deposition （LMD）. The microstructure and tensile properties are investigated， and the interfacial forming mechanism and the cause of the high-temperature performance degradation are discussed. The results show that the composite consists of TiC， （W，Ti）C1-x， and the austenitic γ phase. The submicron-thick （W，Ti）C1-x interfacial layer forms between the TiC particles and the matrix. The interfacial layer originates from the partial dissolution of TiC and the diffusion and substitution of W elements during the laser melting deposition process. At room temperature， the ultimate tensile strength （UTS） of the composite reaches 1198.9 MPa， which is 24.3% higher than that of the matrix alloy （964.3 MPa）. However， at 1000 ℃， the UTS of the composite is 128.7 MPa， which is lower than the 162.5 MPa of the matrix alloy， with a decrease of 20.8%. The degradation in high-temperature strength is mainly due to the consumption of W elements in the matrix by the （W，Ti）C1-x interfacial layer， resulting in decrease in its mass fraction and weakening the solid-solution strengthening and dislocation-pinning effects on the matrix.