冷喷涂CoNiCrAlY涂层制备工艺及组织性能研究

Preparation， Microstructure and Properties of Cold Sprayed CoNiCrAlY Coatings

摘要:

CoNiCrAlY合金可用于航空发动机热端部件的高温涂层，其使用性能因制备工艺的不同而呈现出差异。传统热喷涂技术在制备涂层过程中会引入高温热源，可导致材料发生相变，且产生一定的热应力。为消除热应力，需在喷涂至一定厚度后对涂层进行热处理，这导致了热喷涂技术制备大厚度涂层时喷涂效率的降低和成本的增加。围绕航空发动机涡轮外环高温封严涂层新一代制备技术需求，采用高压冷喷涂技术，以氮气为载气，国产CoNiCrAlY粉末为原料，开展了低成本冷喷涂CoNiCrAlY涂层的制备工艺及组织性能研究。实验采用φ100.50 mm 304不锈钢管基体，在69°喷涂角度、5 MPa喷涂压力下，分别在800、850和900 ℃喷涂温度条件下沉积制备了CoNiCrAlY涂层。测量了粉末在不同喷涂温度下的沉积效率，表征了涂层的微观结构、显微硬度和摩擦磨损性能，以1 050 ℃保温5 h随炉冷却方式对涂层进行了真空热处理，研究了热处理后涂层的组织与性能变化。结果显示，涂层孔隙率随喷涂温度的升高而降低（2.07%、0.81%和0.44%），粉末颗粒的沉积效率随喷涂温度的升高而提高（29.7%、32.5%和36.1%），喷涂态涂层的显微硬度与喷涂温度之间无线性关系（585.32、526.21和563.52 HV_0.3）。经真空热处理后，冷喷涂CoNiCrAlY涂层孔隙率均显著降低，均下降至0.4%左右。显微硬度显著下降，保持在360 HV_0.3左右。摩擦磨损测试结果表明，较低喷涂温度制备的CoNiCrAlY涂层，经真空热处理后具有更低的磨损率。

Abstract:

CoNiCrAlY alloy can be used as a high-temperature coating for hot end components of aircraft engines， and its performance varies due to different preparation processes. General thermal spraying techniques introduce high-temperature heat sources during the preparation of coatings， which can cause material phase transitions and generate certain thermal stresses. To eliminate thermal stress， it is necessary to heat treat the coating after spraying to a certain thickness， which leads to a decrease in spraying efficiency and an increase in cost when preparing thick coatings using thermal spraying technology. This work focuses on the new generation of preparation technology requirements for high-temperature sealing coatings on the outer ring of aircraft engine turbines. Using high-pressure cold spraying technology and nitrogen as the carrier gas， the preparation process and microstructure properties of low-cost cold spraying CoNiCrAlY coating technology were studied. The experiment used 304 stainless steel pipes with a diameter of 100.50 mm. CoNiCrAlY coatings were deposited at spray temperatures of 800， 850， and 900 ℃ at a spray angle of 69° and a spray pressure of 5 MPa. The deposition efficiency of the powder was measured at different working gas temperatures， and the microstructure， microhardness， and friction and wear properties of the coating were characterized. Three sets of coating samples with different spraying temperatures were subjected to vacuum heat treatment at 1 050 ℃ for 5 hours while cooling in the furnace， and the changes in the microstructure and properties of the coatings after heat treatment were studied. The results show that the porosity of the coating decreases with the increase of spraying temperature， and the deposition efficiency of powder particles increases with the increase of spraying temperature. There is no linear relationship between the microhardness of the sprayed coating and the spraying temperature. After vacuum heat treatment， the porosity of the cold sprayed CoNiCrAlY coating significantly decreased to around 0.4%； The microhardness significantly decreased and remained around 360 HV_0.3； The friction and wear test results show that CoNiCrAlY coatings prepared at lower working gas temperatures have lower wear rates after vacuum heat treatment.