Al2O3/ZrO2涂层在热等静压致密化TiAl基合金粉末过程中对碳钢包套的影响

Effects of Al2O3/ZrO2 Layers on Carbon Steel Capsule During Consolidation of TiAl based alloy powders by HIP

摘要:

由于焊接性能好，成本低，碳钢材料常被用于制作热等静压致密化TiAl基合金粉末的包套。在高温高压下，碳钢包套和TiAl基合金粉末通过原子扩散在扩散区形成脆性相，导致包套失效，并降低TiAl基合金压坯的致密度。为了确保碳钢包套在热等静压致密化TiAl基合金粉末过程中的可靠性，本文利用热喷涂的方法在20#钢包套内壁添加了Al2O3/ZrO2（A-Z）涂层，然后在 。在热等静压试验中，带有A-Z涂层的20#钢包套用于热等静压致密化Ti-46Al-2Cr-2Nb-(W, B)预合金粉末，其工艺为：1523K,2.5小时，130MPa+1603K,0.5小时，130MPa。为了对比，利用没有A-Z涂层的20#钢包套在1523K,3小时，130MPa的工艺参数开展了热等静压致密化试验。利用扫描电镜、电子探针等设施对获得的压坯进行了观测和分析。结果表明：A-Z涂层的加入可以防止脆性金属间化合物的形成。在热等静压过程中，20#钢包套中的Fe原子无法通过扩散的方式与TiAl基合金中的钛原子和铝原子相遇。因此，20#钢包套在热等静压过程中的可靠性得到了保证。此外，通过利用添加A-Z涂层的钢包套获得了完全致密的TiAl基合金压坯。压坯呈现出了近全片层类型的微观组织，其室温下的抗拉强度和延伸率也分别突破了590MPa和2.0%。

Abstract:

Owing to good welding properties and low cost, carbon steel is often used to produce capsules to consolidate TiAl based alloy powders via hot isostatic pressing (HIP). Under high temperature and pressure, the density of TiAl pre-alloyed powders is reduced due to the diffusion of atoms and the capsule fails, forming brittle intermetallics. In order to ensure reliability of the carbon steel capsule, Al₂O₃-ZrO₂ (A-Z) layers was added to the inside wall of the 20# carbon steel capsule via thermal spraying. In the HIP experiment, the capsule with A-Z layers was used to consolidate Ti-46Al-2Cr-2Nb-(W, B) pre-alloyed powders at 1523K and 130 MPa for 2.5 hours, and then treated via HIP at 1603K and 130 MPa for 0.5 hours. To compare, the 20# carbon steel without A-Z layers was formed via processing of Ti-46Al-2Cr-2Nb-(W,B) pre-alloyed powders at 1523K and 130 MPa for 3 hours. The as-formed Hipped capsules were observed under SEM and EDS to evaluate the effects of A-Z layers. The test results reveal that the formation of brittle intermetallics was prevented upon addition of A-Z layers. During HIP, iron atoms of 20# carbon steel capsule could not meet titanium and aluminum atoms in the TiAl based alloy powders by diffusion; hence, the reliability of 20# carbon steel capsules was achieved. In addition, the compactly processed capsule of TiAl based alloy with A-Z layers was fully consolidated and exhibited a fine, nearly full lamellar microstructure. The Tensile strength and elongation of the compact at room temperature surpassed 590 MPa and 2.0% respectively.