重型燃机喷嘴壳体及遮热板热障涂层剥落机制

目的 探究重型燃机喷嘴壳体及遮热板热障涂层剥落机制，为该部件的全寿命管理提供参考。方法 采用等离子喷涂方法，分别制备以06Cr25Ni20不锈钢和Hastelloy X合金为基材的热障涂层试验件，并结合水淬热冲击表征方法与瞬态热力耦合仿真方法，表征热障涂层水淬后的剥落状态，获得热障涂层残余剪应力的分布状态随基材和服役工况的变化行为，揭示热障涂层在多层热失配工况下的剥落机制。结果 在水淬热冲击条件下，2种不同基材的热障涂层试验件表现出类似的剥落行为，但由于基材热膨胀系数的差异，以06Cr25Ni20不锈钢为基材的热障涂层的残余剪应力(70.1 MPa)比Hastelloy X合金基材的热障涂层(52.7 MPa)更大，热冲击寿命更短。在梯度温度载荷下，2种不同基材热障涂层试验件的失效模式不同，前者的最大残余剪应力为39.2 MPa，后者为25.7 MPa。结论 在2种温度载荷下，以Hastelloy X合金为基材的热障涂层具有较低的残余应力和较长的服役寿命。此外，水淬热冲击可以快速表征热障涂层的寿命行为，但其失效模式与实际梯度温度载荷下的失效模式仍有一定区别。

Spalling Mechanism of Thermal Barrier Coating Sprayed on Nozzle Housing and Heat Shield Used in Heavy Gas Turbine

Heavy gas turbines are the power equipment of clean and efficient thermal power energy systems, and are widely used in power generation and other fields. Burners, high-temperature blades, nozzle housing, etc., are the core hot-end components of heavy gas turbines, often suffering high-temperature, high pressure, corrosion, high-strength thermal exchange and other severe conditions. Thermal barrier coating (TBC) is one of the key thermal protection systems for high-temperature components in gas turbines. The state of the TBC is usually comprised of three layers:(1) a ceramic top coat, typically composed of yttria-stabilized zirconia (YSZ); (2) a metallic bond coat, typically composed of NiCoCrAlY; and (3) a superalloy substrate. Since TBCs are mainly subject to the extreme high-temperature condition in the burner, the spalling behavior may occur during the period of engine operation and affect the safe operation of the gas turbine. To explore the spalling mechanism of the TBC of the nozzle housing and the heat shield in the heavy gas turbine burner, the TBC samples were prepared on 06Cr25Ni20 stainless steel and Hastelloy X alloy by plasma spraying method. Combined with the thermal shock experiments by water quenching and the transient thermal-mechanical coupling simulation method, the spalling behavior of the TBC after water quenching was characterized, and the residual shear stress distribution of the TBC was obtained as functions of the substrate material and service conditions, which systematically revealed the spalling mechanism of TBC under thermal mismatch strain. The results indicated that two types of TBC specimens exhibited similar spalling behavior under the thermal shock test by water quenching, but the TBC sprayed on Hastelloy X alloy had a smaller residual shear stress (52.7 MPa) than the TBC spray on the 06Cr25Ni20 stainless steel (70.1 MPa) and exhibited a longer lifespan under thermal shock test by water quenching due to the difference in thermal expansion coefficients of the two substrates. Both edge sides of the semicircular hole in the nozzle housing, the middle large circular hole, the small circular hole and the heat shield were high residual shear stress areas. In addition, the accumulated residual shear stress levels and distribution of TBC sprayed on the 06Cr25Ni20 stainless steel and Hastelloy X alloy as substrates under the real gradient temperature boundary conditions were characterized by finite element simulation. The maximum residual shear stress was 39.2 MPa and 25.7 MPa respectively and the corresponding failure modes showed large differences. The connection area between the large circular hole and the semicircular hole, the other side of the large circular hole, both sides of the small circular hole and the inner two sides of the heat shield were high shear stress areas. In summary, the thermal shock test by water quenching can quickly characterize the lifespan of TBC, but the failure mode is different from the actual failure mode. At the same time, TBC sprayed on low thermal expansion coefficient alloys such as Hastelloy X alloys has lower residual stress levels and longer service lives. These results may provide a reference for revealing the spalling mechanism and optimizing the substrate materials of the TBC system in the burner.