论文总字数：21622字

摘 要

奥氏体不锈钢拥有优异的综合性能和良好的抗腐蚀性能，在工业生产中不可或缺。但与其他材料相比，奥氏体不锈钢的表面硬度和表面强度一般，严重制约了不锈钢设备的性能和寿命。尤其是那些要求高硬度，抗疲劳和耐磨损，同时又需要抗腐蚀性能的苛刻环境。

预应变的304不锈钢在经过470℃，30h低温气体渗碳后，在金相显微镜下，可以观察到亮白的渗碳层，且 304不锈钢中因形变诱发的马氏体经过低温气体渗碳处理后转变为扩张奥氏体。在低温气体渗碳过程中，预应变引起的位错密度的增加和形变马氏体含量的增加，并不会促进渗碳层的增长，304奥氏体不锈钢渗碳层厚度分别稳定在26μm左右。渗碳后，两种材料的表面硬度和表面残余应力提高显著，主要强化机理为固溶强化与塑性预应变量无关。

通过动电位极化曲线测试实验，对3.5%NaCl的溶液中低温气体渗碳的预应变304奥氏体不锈钢进行腐蚀性能研究，结果表明：低温气体渗碳的未预应变试样腐蚀性能一般不会降低；经低温气体渗碳后预应变的304奥氏体不锈钢电化学腐蚀性能没有影响；经低温气体渗碳后的预应变 304奥氏体不锈钢电化学腐蚀性能与塑性预应变量有关，15%塑性预应变之前，渗碳后预应变304试样的腐蚀性能没有影响，15%塑性预应变以后，渗碳后预应变304试样线性极化电阻降低，自腐蚀电位正移，抗腐蚀性能随着预应变量提高而下降。

关键词：预应变 304奥氏体不锈钢 低温气体渗碳 腐蚀性能

ABSTRACT

Austenitic stainless steels (ASSs) are the indispensable materials in the industrial production due to their good integrated performance and the excellent corrosion resistance. However, they have only modest surface strength and hardness compared to other steels, influencing their performance and lifetime in many applications, especially in the fields where surface hardness, fatigue resistance and wear resistance are of crucial importance, meanwhile the good corrosion resistance is needed.

After 470℃, 30h low temperature gas carburizing, the 304 stainless steel can be observed bright white carburized layer. Besides, martensite disapper in the bright white carburized layer when deformation exceed 15% for the 304 stainless steel.Different dislocation density and the change of martensite content in 304 stainless steel have no effect on the diffusion of carbon atoms in the process of low temperature gas carburizing.The carburized layer thickness of 316L and 304 are all stable at 35μm and 26μm.Strengthenging mechanism of the two materials is mainly due to interstitial solid solution strengthening and which have extraordinary surface hardness and residual stress.

Potentiodynamic curve test experiment is used to research corrosion resistance of the 304 and 304 stainless steel carburizied layer in 3.5%NaCl solution, the results show that: the low temperature gas carburizing strengthening technology does not reduce the corrosion resistence of austenitic stainless which have no pre-strain.Pre-strain has no effect on the electronchemical corrosion resistence for 304 carburized layer.But carburized layer electrochemical corrosion resistance related to plastic deformation for the 304 steel.The corrosion resistance of the 304 steel carburized layer keep same as the untreated sample before 15% plastic deformation .More than 15% of the pre-strain, linear polarization resistance is reduced ,the corrosion potential negative shift, corrosion resistence of the pre-strain 304 steel after low temperature gas carburing decreased with the increase of the deformation.

Keywords: pre strain austenitic stainless steel low temperature gas carburizing corrosion property

目 录

摘要 1

ABSTRACT 2

第一章 绪 论 1

1.1 课题的研究背景及意义 1

1.2 预应变对奥氏体不锈钢性能的影响 2

1.2.1预应变塑性强化基本原理 2

1.2.2 塑性变形诱发奥氏体不锈相变与位错密度的研究 3

1.2.3马氏体相变对不锈钢耐腐蚀性能的影响 3

1.3 低温气体渗碳 4

1.3.1低温气体渗碳工艺简介 4

1.4 本课题的研究内容与方法 5

第二章 304奥氏体不锈钢预应变试验研究 6

2.1内容与方法 6

2.1.1试验材料与试样制备 6

2.1.2预应变试验 6

2.1.3α´马氏体含量测量 8

2.2结果与讨论 9

2.2.1预应变显微形貌分析 9

2.2.2马氏体相变 10

2.2.3表面硬度及表面残余应力 11

2.3本章小结 12

第三章 预应变对304不锈钢低温气体渗碳效果的影响 13

3.1内容与方法 13

3.1.1试验材料与试验装置 13

3.1.2低温气体渗碳试验 14

3.2结果与讨论 15

3.2.1 渗碳层显微形貌与物相 15

3.3本章小结 18

第四章 预应变304不锈钢低温气体渗碳后的电化学腐蚀性能研究 19

4.1 试样制备与试验方法.........................................................................................................................19

4.1.1 试验材料及试样制备................................................................................................................19

4.1.2 实验装置与方法........................................................................................................................20

4.2 结果与讨论.........................................................................................................................................21

4.2.1 线性极化电阻测量结果分析................................................................................................21

4.2.2 极化曲线测量结果...................................................................................................................22

4.3 本章小结.................................................................................................................................................23

第五章 结论.....................................................24

参考文献 25

致 谢 27

第一章 绪 论

1.1 课题的研究背景及意义

随着科技的发展，石油化工、能源、冶金等工业中装置日益向自动化、高速化、长寿命方向发展，服役环境越来越恶劣，工作的零部件在恶劣的工作环境下容易过早失效，导致整个设备停运，甚至酿成重大事故。根据发达国家的统计数据显示，目前每年因腐蚀造成的财产损失约在6000~10000亿美元，大概是台风，地震等自然灾害财产损失总和的7倍。随着能源的日趋缺乏和可持续发展的要求，提高设备的使用寿命、可靠性和效率，对国民经济的发展有十分重要的作用。

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