Effects of TiC addition on the hot corrosion behavior of IN718 fabricated by laser direct metal deposition

The hot corrosion behavior and mechanism of the IN718 nickel-chromium alloy (Sample D1) and 1 wt % TiC-reinforced IN718 (Sample D2) fabricated by laser direct metal deposition (DMD) in a 75 wt % Na₂SO₄ + 25 wt % NaCl saturated mixed molten salt at 700 °C were studied. After a 100-h test, the weight loss ratio of Sample D1 was 2.4 times that of Sample D2, and the corrosion rate of Sample D1 was 1.5 times that of Sample D2. Chlorination, sulphidation, and oxidation, as well as a change in the acidity at the molten salt interface of the alloy, led to serious spalling of Sample D1. However, the addition of TiC refined the grains, resulting in rapid diffusion of Cr to the alloy surface and formation of a Cr₂O₃ protective layer at high temperatures. In addition, the diffusion of Ni, Fe, etc., was hindered by TiC particles inside the superalloy, which reduced the thickness of the hot corrosion product layer by about 26% and improved the hot corrosion resistance of Sample D2.