加热源对38CrMoAl钢氮化层组织及性能的影响
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摘要
目的研究电磁感应加热、等离子轰击以及电阻热效应在氮化过程中对氮化层组织性能的影响规律。方法通过电磁感应真空脉冲氮化、等离子氮化以及真空氮化技术,对38CrMoAl钢进行氮化处理,并利用光学显微镜、SEM、X射线衍射仪、电子背散射衍射、自动显微硬度仪等仪器,对氮化层的微观形貌、相成分、晶体形态、硬度梯度等进行测试分析。结果 38CrMoAl钢经三种方式分别氮化后,氮化层主要为Fe_2N、Fe_3N相结构,晶粒以0.5～2.5μm的小尺寸晶粒为主,取向差以小于5°的取向差为主。电磁感应加热容易导致氮化层中白亮层较厚,ε相含氮量高,表面硬度达到1200HV_(0.5),但过渡层的界面不平整。等离子轰击下的氮离子扩散能力相对较强,致使38CrMoAl钢氮化层厚度高达240μm,0.5～2.5μm的小晶粒和小于5°的取向差分布分别为81%、73%。电阻加热的真空氮化,氮化层厚度仅为90μm,氮化层小尺寸晶粒和小角度取向差的分布分别为76.4%和71.9%。结论在氮化过程中,电磁感应加热集肤效应有助于氮化层获得高氮含量和较高表面硬度。等离子轰击能加强氮原子扩散和细化晶粒组织,获得优良的组织及性能。而电阻加热方式不能提供能量集中的反应环境,氮化效率和氮化层性能均弱于前两者。
The work aims to study the influence rules of the heating mechanism of electromagnetic induction,plasma bombardment and resistance heat on the microstructure of nitriding layer in nitriding process.38CrMoAl steel was treated by electromagnetic induction vacuum pulse,plasma and vacuum nitriding technology.OM,SEM,XRD,EBSD and automatic microhardness tester were carried out to detect and analyze the microstructures,phase composition,crystal phase and hardness gradient of these nitriding layers.After 38CrMoAl steel were nitrided by three methods respectively,the nitriding layers were mainly Fe_2N and Fe_3N phase structure,and small-sized crystal grains of 0.5～2.5μm and misorientation of less than 5°were distributed.The electromagnetic induction heating facilitated the nitriding layer to obtain a higher content ofεphase and a thicker white bright layer,resulting in a surface hardness of 1200HV_(0.5) and uneven transition layer.Under the plasma bombardment,the nitrogen ion diffusion ability was relatively strong,resulting in the thickness of the nitriding layer of 38CrMoAl steel up to 240μm and the distribution of small grain size of 0.5～2.5μm and the misorientation of less than 5°were 81%and 73%respectively.However after the vacuum nitridation of 38CrMoAl steel by resistance heating,the thickness of the nitriding layer was only 90μm,and the distribution of the small-sized grain and the small angle misorientation in the nitriding layer were 76.4%and 71.9%.The skin effect of electromagnetic induction heating helps the nitriding layer to obtain high nitrogen content and high surface hardness.Plasma bombardment enhances the diffusion of nitrogen atoms and refines the microstructure of the grains,and obtains excellent microstructure and performance.The resistance heating method cannot provide a concentrated reaction environment,so the nitriding efficiency and the nitride layer performance are weaker than the former two.
The work aims to study the influence rules of the heating mechanism of electromagnetic induction,plasma bombardment and resistance heat on the microstructure of nitriding layer in nitriding process.38CrMoAl steel was treated by electromagnetic induction vacuum pulse,plasma and vacuum nitriding technology.OM,SEM,XRD,EBSD and automatic microhardness tester were carried out to detect and analyze the microstructures,phase composition,crystal phase and hardness gradient of these nitriding layers.After 38CrMoAl steel were nitrided by three methods respectively,the nitriding layers were mainly Fe_2N and Fe_3N phase structure,and small-sized crystal grains of 0.5～2.5μm and misorientation of less than 5°were distributed.The electromagnetic induction heating facilitated the nitriding layer to obtain a higher content ofεphase and a thicker white bright layer,resulting in a surface hardness of 1200HV_(0.5) and uneven transition layer.Under the plasma bombardment,the nitrogen ion diffusion ability was relatively strong,resulting in the thickness of the nitriding layer of 38CrMoAl steel up to 240μm and the distribution of small grain size of 0.5～2.5μm and the misorientation of less than 5°were 81%and 73%respectively.However after the vacuum nitridation of 38CrMoAl steel by resistance heating,the thickness of the nitriding layer was only 90μm,and the distribution of the small-sized grain and the small angle misorientation in the nitriding layer were 76.4%and 71.9%.The skin effect of electromagnetic induction heating helps the nitriding layer to obtain high nitrogen content and high surface hardness.Plasma bombardment enhances the diffusion of nitrogen atoms and refines the microstructure of the grains,and obtains excellent microstructure and performance.The resistance heating method cannot provide a concentrated reaction environment,so the nitriding efficiency and the nitride layer performance are weaker than the former two.
引文
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[18]范航京,梁益龙,邹雄,等.42CrMo钢等离子氮化和水射流喷丸复合处理[J].中国表面工程,2016,29(6):23-29.FAN Hang-jing,LIANG Yi-long,ZOU Xiong,et al.Composite treatment of water jet shot peening combined with plasma nitriding on 42CrMo Steel[J].China surface engineering,2016,29(6):23-29.
[2]ZHANG L Z,ZHANG H,DING L Y.Using the vacuum ion nitriding process to improve the quality of 38CrMoAIAcylinder[J].Advanced materials research,2015,1089:93-96.
[3]王博,孙淑华,郭明伟,等.不锈钢固溶渗氮工艺与技术的研究进展[J].材料热处理学报,2014,35(6):1-9.WANG Bo,SUN Shu-hua,GUO Ming-wei,et al.Research progress in solid solution nitriding process and technology for stainless steels[J].Transactions of materials and heat treatment,2014,35(6):1-9.
[4]WANG B,SUN S,GUO M W,et al.Study on pressurized gas nitriding characteristics for steel 38CrMoAlA[J].Surface&coatings technology,2015,279:60-64.
[5]CHEN Y,SONG L,ZHANG C,et al.Plasma nitriding without formation of compound layer for 38CrMoAl hydraulic plunger[J].Vacuum,2017,143:98-101.
[6]陈尧,宋磊,张宸恺,等.38CrMoAl液压柱塞无白亮层低温离子渗氮工艺研究[J].机械工程学报,2017,53(22):81-86.CHEN Yao,SONG Lei,ZHANG Chen-kai,et al.Lower temperature plasma nitriding without white layer for38CrMoAl hydraulic plunger[J].Journal of mechanical engineering,2017,53(22):81-86.
[7]冯治国,郑纪豹,刘静.渗氮温度对38CrMoAl钢真空感应氮化层耐磨性能的影响[J].材料热处理学报,2017,38(10):100-105.FENG Zhi-guo,ZHENG Ji-bao,LIU Jing.Effect of nitriding temperature on wear resistance of vacuum induction nitriding layer of 38Cr Mo Al steel[J].Transactions of materials&heat treatment,2017,38(10):100-105.
[8]冯治国,郑纪豹,刘静.38CrMoAl钢负压感应快速氮化工艺及性能[J].材料热处理学报,2017,38(8):128-133.FENG Zhi-guo,ZHENG Ji-bao,LIU Jing.Negative pressure rapid nitriding process and performance of38CrMoAl steel under vacuum induction[J].Transactions of materials&heat treatment,2017,38(8):128-133.
[9]范航京.等离子氮化及表面强化对42Cr Mo齿轮钢接触疲劳性能的影响[D].贵州:贵州大学,2017.FAN Hang-jing.Effect of plasma nitriding and surface strengthening on contact fatigue properties of 42CrMo gear steel[D].Guizhou:Guizhou University,2017.
[10]雷声,黄己立,苏广柱.临界氮势控制及影响因素[J].安徽大学学报(自科版),2004,28(2):54-58.LEI Sheng,HUANG Ji-li,SU Guang-zhu.The control of critical nitro-genpotential and its influencing factors[J].Journal of Anhui University(natural science edition)2004,28(2):54-58.
[11]MICHALSKI J,BURDYNSKI K,WACH P.Nitrogen avail-ability of nitriding atmosphere in controlled gas nitriding processes[J].Archives of metallurgy and materials,2015,60(2):747-754.
[12]SONG M C,MOON Y H.Coupled electromagnetic and thermal analysis of induction heating for the forging of marine crankshafts[J].Applied thermal engineering,2016,98:98-109.
[13]刘沅东,王成彪,车延岗,等.离子轰击热处理技术对轴承钢摩擦学性能的影响[J].机械工程学报,201147(5):126-133.LIU Yuan-dong,WANG Cheng-biao,CHE Yan-gang,et al.Ttibological properties of 52100 steel treated by different plasma bombardment heat treatment method[J].Journal of mechanical engineering,2011,47(5):126-133.
[14]李敏,李惠东,李惠琪,等.等离子体表面改性技术的发展[J].金属热处理,2004,29(7):5-9.LI Ming,LI Hui-dong,Li Hui-qi,et al.Development of plasma surface modification technology[J].Heat treatment of metals,2004,29(7):5-9.
[15]杨卓立,廖海峰,孙迪,等.等离子体辅助球磨对Al+C4H4N4合成超细AlN的影响机制[J].中国有色金属学报,2018,28(8):1587-1596.YANG Zhuo-li,LIAO Hai-feng,SUN Di.et al.Effect of plasma-assisted ball milling on the synthesis of ultrafine Al N by Al+C4H4N4[J].The Chinese journal of nonferrous metals,2018,28(8):1587-1596.
[16]COJOCARU M O,DRAGOMIR D,DRUGA L.Effects of electromagnetic induction on growth kinetics of case hardened layers[J].International heat treatment&surface engineering,2013,7(1):38-42.
[17]夏冬生,杨平,谢利,等.升温速率对低碳无取向电工钢脱碳退火组织及织构的影响[J].金属学报,2014(12):1437-1445.XIA Dong-sheng,YANG Ping,XIE Li,et al.Influence of heating rate on the decarburized annealing microstructure and texture in low-carbon non-oriented electrical steel[J].Acta metallurgica sinica,2014(12):1437-1445.
[18]范航京,梁益龙,邹雄,等.42CrMo钢等离子氮化和水射流喷丸复合处理[J].中国表面工程,2016,29(6):23-29.FAN Hang-jing,LIANG Yi-long,ZOU Xiong,et al.Composite treatment of water jet shot peening combined with plasma nitriding on 42CrMo Steel[J].China surface engineering,2016,29(6):23-29.