Microstructure and Mechanical Properties of Carbides Reinforced Nickel Matrix Alloy Prepared by Selective Laser Melting

Selective laser melting was used to prepare the ceramic particles reinforced nickel alloy owing to its high designability, high working flexibility and high efficiency. In this paper, a carbides particles reinforced Haynes 230 alloy was prepared using SLM technology to further strengthen the alloy. Microstructures of the carbide particles reinforced Haynes 230 alloy were investigated using electron microscopy (SEM), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). Meanwhile, the tensile tests were carried out to determine the strengths of the composite. The results show that the microstructure of the composite consisted of uniformly distributed M23C6 and M6C type carbides and the strengths of the alloy were higher than the matrix alloy Haynes 230. The increased strengths of the carbide reinforced Haynes 230 alloy (room temperature yield strength 113 MPa increased, ~ 33.2%) can be attributed to the synergy strengthening including refined grain strengthening, Orowan strengthening and dislocation strengthening.

A Comparison of Weldability, Structure, and Mechanical Properties of CM64 and Tribaloy T-800 Welds for Hard-Facing of Turbine Blades

In this study, the weldability, microstructure, and tensile properties of CM64 and Tribaloy T-800 (T800) cobalt-based hard-facing materials were studied. Successful CM64 hard-facing could be achieved at ambient temperature using manual gas tungsten arc welding (GTAW-MA). It was shown that T800 welded at ambient temperature was prone to cold cracking due to a combination of low ductility with high welding stresses that limited the accommodation of residual stresses by plastic deformation within the weld beads. Sound T800 welds of various geometries and sizes were produced on cobalt- and nickel-based X-40 and Haynes 230 superalloys, respectively, using GTAW-MA when preheating above 900 °C was used. Microstructural analyses on the sound CM64 and T800 welds were performed using optical and electron microscopy and X-ray diffraction. The distribution of elements and phases in each alloy was evaluated and revealed the epitaxial dendritic structure with the Cr–W–Si-based phase in the interdendritic region in CM64 welds compared with petal-like and equiaxed hard Mo–Co–Si-based dendrites and fine particles in T800. Tensile testing from room temperature up to 1093 °C was performed on both alloys. T800 welds possessed lower ultimate tensile strengths and elongations in this temperature range when compared with the CM64 alloy. Recommendations for hard-facing of turbine engine components were provided.