摘要气阀是内燃机的关键组成部件，它的性能直接影响内燃机的使用安全，高温、高 压的腐蚀性燃气环境对气阀材料提出了极为苛刻的要求。镍基合金组织稳定、性能优 异，在高温环境中应用广泛，本文选用了江苏申源特钢有限公司提供的镍基气阀合金。79864

本文研究了该合金材料的固溶处理及随后的时效强化工艺，通过硬度测试、金相 观察及 XRD 分析，确定材料的最佳热处理工艺参数，利用 SEM 观察时效强化相的 显微形貌。试验的固溶温度是 1050℃~1150℃，固溶处理后，测试表面显微硬度，观 察表面金相组织的变化，确定最佳的固溶工艺为 1100℃×1h，该工艺下获得最大硬 度为：341。0HV0。5。随后的对固溶 1h 后的试样进行 XRD 分析，选择的标准物相为 Cr-Ni-Fe-C 奥氏体相，发现 1100℃时各个峰的相对偏移均较小，可见在该温度下处理 能获得较好的固溶度。与硬度分析结果相一致，表明在 1100℃×1h（AC）能获得相 对最佳的晶粒组织及固溶度，有利于随后的时效处理。

试验的时效温度是 850℃和 750℃，时效最长时间为 12h，在 850℃下时效保温时， 硬度略有降低，可能原因是部分已析出 γ′相质点发生了回溶，导致材料的整体硬度降 低。在 750℃下时效保温，类似试样的显微硬度持续增加，12h 后硬度达到 358。0 HV0。5。 参照类似合金的标准热处理工艺（1100℃×1h, AC。+850℃×4h, AC。+750℃×4h, AC。）， 试样硬度达到 379。2HV0。5，晶粒内部有大量 γ′时效强化析出，与基体保持共格关系， 部分晶界处有富 Nb 碳化物析出。

毕业论文关键词：镍基高温合金；气阀钢；固溶强化；时效析出强化

Abstract Valve is a key component part of the internal combustion engine, its performance directly affects the safety of the engine。 The working environment, high-temperature, high-pressure with corrosive gas, presentes extremely demanding to the valve materials。 Nickel based alloys are widely used in high temperature environment, and the stability and performance of Ni based alloys are excellent, materials used in this study are Special Steel Co。, Ltd。 Jiang Su Shenyuan nickel-based alloy valves。

The solid solution treatment and the subsequent aging strengthening technology of the alloy were studied through hardness testing, metallographic observation and XRD analysis, the material to determine the optimum heat treatment process parameters and observed by SEM of strengthening precipitates microstructure。 Solid solution temperature is 1050℃ to 1150℃,after solution treatment, testing the surface micro-hardness and observing changes in the microstructure of surface determine optimal solution process for 1100℃1h, AC。, the technology to obtain the maximum hardness is 341。0HV0。5。 Subsequent to the solid solution 1h after samples were analyzed by XRD, choice standard phase is Cr-Ni-Fe-C austenite phase was found to 1100℃ when the offsets for each peak are small, visible in the temperature treatment can obtain good solubility。 And hardness analysis are consistent。 The results show that in 1100 ℃ 1h, AC。 can be obtained relatively optimum microstructure and solid solubility, which is in favor of the subsequent aging treatment。

Test aging temperature is 850℃ and 750℃ and the maximum time for the aging is

12h。 When the heat aging at 850℃, the hardness decreased, because some of the γ ' phase particles which have been precipitated may dissolve back,it has resulted in overall lower hardness of the material。 Aging at 750℃ under the insulation, the hardness continued to increase which is similar to the sample until hardness get 358。0HV0。5 12h later。 With reference to the similar alloys standard heat treatment process (1100℃×1h, AC。+850℃× 4h, AC+750℃×4h, AC。), the hardness reached 379。2HV0。5, grain interior has a lot of γ' aging precipitation strengthening, and the substrate to maintain coherent relationship, some grains have rich Nb carbides。