【作者】 代毅；

【导师】 李宁； 高福全；

【作者基本信息】 四川大学 ， 机械工程， 2002， 硕士

【摘要】 本文在综合分析了激光相变强化处理技术的发展、特点、激光与材料之间的相互作用和工艺过程的基础上，提出了激光相变强化技术的应用存在着工艺的重复性和可移植性较差的问题，特别是4Cr13不锈钢无法利用常规方法进行预处理。为此，本文重点研究了4Cr13不锈钢预处理的工艺方法和配方、添加剂的作用和影响、氧化膜的性能，以及单道激光相变强化技术和整体强化技术，并通过组织结构的分析探讨了强化的机理。还在产品模拟件上进行了工艺验证。得到了以下研究成果： (1)采用铬酐—硫酸体系或者重铬酸盐并用熔融氧化工艺法，都能够成功地对4Cr13不锈钢进行激光相变强化前的预处理。在铬酐—硫酸体系的配方中，GW—1复合添加剂可显著提高预处理的速度，改善氧化膜的致密性、结合强度和外观均匀性，同时还对黑化液具有稳定作用。 (2)获得的黑色氧化膜致密、均匀，耐腐蚀性能、与基体的结合力和耐磨性能都达到了吸光表层的要求，完全满足激光表面强化工艺的需要，使材料对激光吸收率大大提高。 (3)当采用获得的最佳工艺参数时，可使阀芯φ10mm×8mm摩擦部分表面获得均匀的强化层，强化层深度约0.62mm—0.86mm，硬度为41.3HRC—44HRC，满足阀芯的设计使用要求。 (4)激光表面强化组织共分三层，强化层晶粒细小，组织为隐针高碳马氏体，亚结构有较高密度的位错，对阀芯的耐磨性和使用寿命的提高有极大的促进作用。 代毅：4Q13 37sc＄N阀芯剜优相变强化技术研究 （5）激光相变强化工艺参数的硬化层特性影响较大，在产品应用之前必须进行工艺验证。组织的显著细化、高碳马氏体的形成、内部位错的大量增殖是获得强化区高硬度的主要原因。更多还原

【Abstract】 Having analysed synthetically the history, characteristics, interaction between the laser and material and technological procedure, it is put forward that poor technological repetition and transplantation exist when laser transition hardening technique (LTHT) is applied, especially that 4Cr13 stainless steel can not be pretreated with regular method. Therefore, it has been study on pretreatment method, prescription, effect of additive and properties of oxide film for 4Cr13 stainless steel, then the techniques of LTHT on single lane and whole surface, while strengthening mechanism is explored through analyzing the microstructure. Technological verification has also been conducted on the product simulation. Results have been achieved as follow:4Cr13 stainless steel manages to be pretreated before laser transition hardening with chromate-vitriol or dichromate. Within chromate-vitriol prescription, GW-1 additive can raise pretreatment velocity obviously and improve density, combining strength and uniform appearance, as well as stabilize the blacking chemical composition.The dense uniform black oxide film on the surface of material improves the attractive ratio to the laser energy greatly with better corrupt resistance, combining strength and wear resistance, which can totally meet the requirements of LTHT.When appropriate parameters are adopted, a uniform hardened case on ? 10mmx8mm rub part of valve core can be acquired with depth about0.62mm-0.86mm and hardness about 41.3 HRC-44HRC,which meets the perform requirements.The microstructures can be divided into three layers, with the hardening case having finer grains, high carbon martensite with dense dislocation, which can promote wear resistance and perform span.The technological parameters of LTHT can affect the characteristics of hardening case, so verification must be conducted before applying the product. Refining microstructures remarkably, yielding martensites with high carbon, proliferating dislocations greatly are the main causes of surface hardening.更多还原