通过对比服役不同时间后HP40Nb炉管轴向截面不同位置与外表面打磨至一定深度处的组织和硬度变化，分析利用复膜金相技术与现场硬度测试来评估在役炉管损伤的可行性。结果表明：在高温下服役较长时间后，炉管轴向截面不同位置的组织，尤其是碳化物形貌差异较明显，甚至会因超温而出现孔洞，导致炉管发生早期失效；服役炉管轴向截面不同位置处的硬度差异较大，越靠近壁厚中心硬度越高，与组织变化规律相符；打磨炉管表面，测定一定深度处的硬度，当硬度持续稳定时，可用该深度处的组织来表征炉管大部分的组织，这验证了复膜金相技术和现场硬度测试用于评价服役HP40Nb炉管组织损伤的可行性。

Microstructure and hardness changes at different positions on axial section and at certain depths from outer surface by grinding HP40Nb furnace tube after service for different times were compared, and then the feasibility of cladding metallographic technique and on-site hardness test in evaluating the damage of furnace tube in service was analyzed. The results show that after service of the furnace tube at high temperature for a long time, the microstructure of different positions on axial section, especially carbide morphology, was significantly different, and even holes appeared because of overheating, which led to the early failure. The hardness at different positions on the axial section varied greatly, and the closer to the wall thickness center, the higher the hardness, which was consistent with the changes of microstructure. The surface of furnace tube was ground, and the hardness at certain depth was measured; when the measured hardness continued to be stable, the microstructure at this depth could characterize most of the microstructure of the furnace tube. This verified the feasibility of cladding metallography and on-site hardness test for evaluating the microstructure demage of HP40Nb furnace tubes in service.