10th International Conference on Surface Engineering (ICSE 2026)

Municipal solid waste incineration generates aggressive alkali metal molten salts and SO₂/O₂/H₂O-containing flue gases, causing severe high-temperature corrosion of boiler tubes. Herein, a surface engineering strategy based on laser cladding was developed to fabricate Stellite 6 Co-based coatings and Co-based/Ti₃SiC₂ composite coatings on 304 stainless steel. Orthogonal experiments optimized the processing parameters to a laser power of 2 kW, scanning speed of 660 mm/min, powder feeding rate of 1.1 r/min, and overlap rate of 50%. Cyclic oxidation tests were conducted in air at 600–800 °C for 240 h, and hot corrosion tests were performed at 600 °C for 168 h under a KCl–Na₂SO₄ deposit in an SO₂/O₂/H₂O atmosphere. The Co-based coating exhibited superior corrosion resistance compared with TP347H steel, forming a dense Cr₂O₃-rich scale with CoCr₂O₄ and NiFe₂O₄ spinels, along with internal Cr₂S₃ and SiO₂. In contrast, TP347H steel formed a loose Fe₂O₃/FeS scale that spalled readily. The cyclic oxidation resistance was temperature-dependent, with mass gains of ~0.1, 0.35, and 0.43 mg at 600, 700, and 800 °C, respectively. Ti₃SiC₂ addition refined the microstructure and non-monotonically influenced the corrosion resistance. The coating with 4 wt.% Ti₃SiC₂ exhibited optimal protection, forming a continuous ~10 μm-thick scale and a shallow internal corrosion zone of ~20 μm. During laser cladding, Ti₃SiC₂ partially decomposed into TiC and free C, leading to in-situ formation of Cr₇C₃. These phases pinned grain boundaries, refined grains, increased grain-boundary area, and promoted Cr diffusion to form dense Cr₂O₃. CoTiO₃ also formed as a protective phase. Excessive Ti₃SiC₂ (>6 wt.%) increased dilution and Fe incorporation, resulting in loose and cracked scales and degraded performance. This work demonstrates that laser-cladded Co-based/Ti₃SiC₂ composite coatings are a promising surface engineering solution for high-temperature alkali metal molten salt corrosion protection in waste-incineration boilers.

Laser cladding; Co-based coating; Ti₃SiC₂; High-temperature corrosion; Waste incineration