Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： With the fast development of industry, pollution becomes a very serious problem. The industrial and life wastewater are discharged and cause the environment pollution. Supercritical water oxidation (SCWO) becomes the most effective method to treat the wastewater. But the material used in the equipment plays a key role in restricting the application of the SCWO process. Currently, during the SCWO wastewater treatment process, 304 austenitic stainless steel, Alloy 625, P91 and P92 steels are the main preheater and reactor materials. In order to reduce the serious corrosion and improve economic efficiency of the materials for this process, a new corrosion resistant Ni-based alloy X-2# alloy has been developed with an aim of replacing the previous ones. In particular, it is highly important to the related behavior of this new alloy welding with the original SCWO. Therefore, the microstructure and mechanical properties of the welding joint of the new alloy and alloy 625 with manual argon arc welding were investigated. The microstructure and fracture morphologies of the welding joint were analyzed by OM, SEM and EDX. The micro- hardness, tensile strength and other mechanical properties were tested and analyzed. The results indicated that more isometric crystals in remelting zone to improve the welding seam strength and the microstructure in fusion zone of X-2# side did not show welding defects. However, some NbC and Laves phases formed near the fusion zone of 625 alloy sides, which affected the mechanical properties of material. Due to the influence of two thermal cycles near the remelting zone, the grains of heat affected zone (HAZ) were easy to grow. But the thermal stability of X-2# side HAZ could reach excellent level. Fine grains of 625 parent material led to grain growth seriously in HAZ, which reduced its Vickers hardness. Because of the tensile strength of welding joints of room temperature and 500 ℃ was lower than the parent materials, the welding seam could be the weakest link. The tesile fracture of X-2#/625 dissimilar metal welding joint was dimple morphology.
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-04 Cooperative journals: 《金属学报》
Abstract：通过对一种新型镍基耐蚀合金(X-2#)手工氩弧焊接接头拉伸性能和硬度的测试，并结合OM，SEM和EDS等技术系统研究了焊接接头的组织和性能。结果表明，X-2#合金焊接接头焊缝区为铸态组织，熔合区从基体到焊缝金属组织过渡良好，热影响区没有晶粒明显粗化现象，母材晶粒度为5级有利于接头的焊接。新合金焊缝区的维氏硬度值小于基体，但焊缝重熔区的维氏硬度值由于等轴晶数量增多而变大。合金中W和Mo等固溶强化元素及Al和Ti沉淀强化元素使X-2#合金焊接接头具有较好的高温强度及热稳定性。合金焊接接头室温与高温下的抗拉强度均低于母材，焊接系数η大于88%，焊缝区为接头最薄弱环节，拉伸断口均为韧性断口，断裂机制为正断与剪切断的混合断裂。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-04 Cooperative journals: 《金属学报》
Abstract：通过对一种新型镍基耐蚀合金U26-2#与625合金手工氩弧焊接接头拉伸性能和硬度的测试，并结合OM，SEM和EDS分析等手段研究了焊接接头的组织和性能。结果表明，U26-2#/625异种金属焊接焊缝重熔区等轴晶组织增多，有利于提高焊缝区强度。U26-2#合金一侧熔合区组织过度良好，而625合金一侧晶界有NbC和Laves相析出，影响材料的力学性能。热影响区在靠近重熔区附近的晶粒由于受2次热循环的影响，出现晶粒长大现象，而U26-2#合金一侧热影响区的热稳定性较好。625合金母材晶粒细小导致其热影响区晶粒长大明显，从而使625合金一侧热影响区的维氏硬度值降低。U26-2#/625焊接接头在室温到700 ℃下的抗拉强度均低于2侧母材，焊缝区为接头最薄弱环节，断口形貌均为韧窝状的韧性断口。
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