使用VZ2106填料真空硬銲三種基材之研究

Abstract

本實驗使用VZ2106填料合金，分別進行真空硬銲接合鎳鐵基（Incoloy 800）及鐵基（316L 、304L Stainless Steel）等三種合金。VZ2106填料中因為以Ni取代了部分的Fe，所以在強度與抗腐蝕能力上，較傳統填料提升許多。研究中藉由調整硬銲製程中的硬銲溫度、持溫時間與填料厚度進行接合，透過掃描式電子顯微鏡觀察接合後銲道的顯微結構與析出物分佈狀況，再透過EPMA分析析出物的化學組成。此外，也將材料做成剪力試片以測試材料接合的強度，再對破壞的銲點進行破壞形貌分析與斷裂位置分析，以探討顯微組織與剪力強度的關係。 實驗結果顯示，使用VZ2106合金真空硬銲IN-800、316L和304L皆會在銲道界面處產生BCrFe化合物，此種硼化物極為脆性，其生成對於銲點整體強度而言相當不利。由於硼原子在304L與316L基材中的擴散較慢，故在相同硬銲製程條件下，所生成的BCrFe介金屬化合物比IN-800基材為少。實驗中亦發現持溫時間增加時，硼原子所形成的介金屬化合物會因為較長的擴散時間而逐漸地消失。提升硬銲溫度的效果與增加持溫時間的效果類似，也會使BCrFe化合物的量明顯減少。剪力測試結果也顯示出，破裂位置皆位於BCrFe脆性相上，且IN-800/316L與IN-800/304L異質硬銲接點的破壞位置皆位於IN-800與銲道界面處。硬銲接合強度以304L表現最為出色，其次是316L與IN-800，所有硬銲接點之強度幾乎都大於400MPa，也代表著這樣的硬銲合金組合是可以被應用在工業上。

In this research, VZ2106 filler metal has been applied in the vacuum brazing of three substrates, Nickel/Iron base alloy (Incoloy 800), Ferrous alloy (316L and 304L Stainless steel), respectively. Part of Fe is replaced by Ni in the VZ2106 filler metal, so strength and corrosin resistance are superior to traditional fillers. Brazing was performed by controlling parameters such as brazing temperature, holding time and filler thickness. The microstructure of vacuum brazed joints and distribution of precipitates were observed by SEM, followed by the EPMA quantitative chemical analysis. Brazed joints were made to be conducted by shear test. The relationship between microstructure and shear strength was discussed by failure analyses of fractured surface and its cross section. For IN-800/VZ2106/IN-800, 316L/VZ2106/316L and 304L/VZ2106/304L brazed joints, interfaces of brazing area contained BCrFe intermetallics. They deteriorated the final joint strengths due to the brittleness of precipitates. With the same brazing parameters, the amount of BCrFe intermetallics was less in 316L and 304L joints than that in IN-800 joint, because the diffusion rate of boron in the latter was faster. The results also showed that the precipitates were eliminated from the joint due to the longer holding time, since the boron had more time to diffuse. The effect of raising brazing temperature was the same as that of holding time. The results of shear test showed that all fracture sites appeared at BCrFe intermetallics, and the fracture sites of IN-800/VZ2106/316L and IN-800/VZ2106/304L were located at the IN-800 side. Shear strength of 304L joint was the best, followed by 316L and IN-800 joints. Shear strengths of three substrates were higher than 400 MPa, so the combination of these alloys can be used in industry.