Thermodynamic properties of the NiSO₄–K₂SO₄ system play significant roles in various applications, e. g. in gas turbine components. In these components, Ni-base superalloys and coatings often suffer from the so-called hot corrosion induced by alkali sulphate deposits. In the present work, the phase equilibria in the system NiSO₄–K₂SO₄ were experimentally determined for the first time using differential thermal analysis (DTA), dilatometry (DiL) and X-ray diffraction method (XRD). Two eutectic points and two stoichiometric compounds, K₂Ni₂(SO₄)₃ and K₂Ni(SO₄)₂, were found in this system. The temperature and composition of the lower eutectic were determined to be 642 °C and 40 mol.% NiSO₄, respectively. Another eutectic between NiSO₄ and K₂Ni₂(SO₄)₃ was found at 819 °C, and the corresponding composition is around 75 mol.% NiSO₄ and 25 mol. % K₂SO₄. Based on the obtained experimental data, the NiSO₄–K₂SO₄ system was thermodynamically assessed using the CALPHAD methodology. The modified associate species model was used for the description of the liquid phase. Using the optimized dataset, the calculated phase diagram showed a good agreement with the experimental results. This dataset extends the previously developed general sulphate database including alkali- and alkaline-earth sulphates (CaSO₄–MgSO₄–Na₂SO₄–K₂SO₄) with the addition of NiSO₄.

NiSO ₄ –K ₂ SO ₄系统的热力学特性在各种应用中发挥着重要作用，例如在燃气轮机部件中。在这些部件中，镍基高温合金和涂层经常遭受由碱性硫酸盐沉积物引起的所谓的热腐蚀。在目前的工作中，首次使用差热分析 (DTA)、膨胀法 (DiL) 和 X 射线衍射法 (XRD) 通过实验确定了系统 NiSO ₄ –K ₂ SO ₄中的相平衡。两个共晶点和两种化学计量化合物，K ₂ Ni ₂ (SO ₄ ) ₃和 K ₂ Ni(SO₄ ) ₂、在本系统中发现。低共晶的温度和成分分别确定为 642 °C 和 40 mol.% NiSO ₄。在 819 °C 下发现了NiSO ₄和 K ₂ Ni ₂ (SO ₄ ) ₃之间的另一种共晶，相应的成分约为 75 mol.% NiSO ₄和 25 mol. % 。% K ₂ SO ₄。根据获得的实验数据，NiSO ₄ –K ₂ SO ₄使用 CALPHAD 方法对系统进行热力学评估。改进的关联物种模型用于描述液相。使用优化的数据集，计算出的相图与实验结果吻合良好。此数据集扩展了先前开发的一般硫酸盐数据库，包括碱金属和碱土硫酸盐（硫酸钙₄ -MgSO ₄ -Na ₂ SO ₄ -K ₂ SO ₄）在加入的NiSO的₄。