【作者】 王国阳；

【导师】 王德和；

【作者基本信息】 大连理工大学 ， 材料学， 2006， 硕士

【摘要】 目前,渗硼尤其是硼钒共渗和稀土硼钒共渗的工艺、组织及性能方面尚存在不少问题,仍缺乏系统的实验数据和较为全面的分析结论。为了给工业生产提供理论指导,推动渗硼及含硼多元共渗在工业上的进一步应用,本文以中低碳钢为待渗基体,采用固体粉末法进行了渗硼、硼钒共渗以及稀土硼钒共渗工艺实验。首先设计了正交实验方案,通过改变渗剂配方和工艺参数进行了一系列工艺实验,根据所得渗层厚度和显微硬度的大小来分析渗剂配方、工艺参数对渗层结构和性能的影响规律,从而为这三种工艺确定了合理的渗剂配方和工艺参数。然后,对经过这三种工艺处理试样的渗层组织形貌、渗入元素含量及分布、物相组成、显微硬度以及脆性等方面进行了全面的检测分析。 研究结果表明:渗硼层厚度随着温度的升高、时间的延长和供硼剂含量的提高而增大,渗硼温度对渗层厚度影响效果最大,共渗时间的影响相对最小;三种工艺的渗层硼化物组织都呈梳齿状锲入基体,硼齿区最外层比次外层更疏松;过渡区有不同程度的增碳和晶粒粗大现象;45钢渗层的梳齿比20钢更加粗大和致密,添加钒铁的共渗改善了渗层的致密性。渗硼层均获得了FeB和Fe₂B的双相组织,随试样含碳量提高,渗硼层中FeB相含量趋于降低。添加钒铁的共渗倾向于抑制FeB相的产生,并可能形成V₂C甚至VB化合物相;硼钒共渗层的显微硬度高于渗硼层,但硬度梯度仍然较大。稀土硼钒共渗层显微硬度受渗入硅的影响而减小,同时硬度梯度也较小;在大载荷作用下,20钢的渗层脆性显著大于45钢渗层,同种材料稀土硼钒共渗层和硼钒共渗层的脆性均大于渗硼层,因此应该对渗硼及含硼多元共渗试样进行淬火和回火处理以提高基体强度。 最后根据实验结果,探讨了各渗层形核长大模型和各元素的微观扩散机制及其对渗层性能的影响。更多还原

【Abstract】 There are many problems about process,microstructure and properties of bonding espencially boron-vanadizing and systematic experiments data and all-rounded analysis are lacked presently. Boridng,boron-vanadizing and RE-boron-vanadizing experiments which adopt solid powder method based carbon steel have been done in this paper for affording academic guidance to industrialized production and propeling more applications of boriding and boron included multicomponent thermochemical treatment in industry.Orthogonal experimental project is designed. A series of process experiments have been done by altering dispensation of permeation reagent and process parameter.The effects of dispensation of permeation reagent and process parameter on structure and properties of the layers have been studied According to thickness and microhardness of the layers,and then rational dispensation of permeation reagent and process parameter are confirmed for the three processes.Then structure pattern,content and distribution of element permeated,phase makeup,microhardness and brittleness for the layers are tested roundly.The results show:thickness of boriding layer increase with temperature rising ,time prolonging and content of boride provided reagent increasing.Boriding temperature has a maximum effect on boriding layers thickness,and boriding time has a minimal effect on boriding layers thickness.Surface of boron tooth zone is more looser than subsurface;the carbon pick-up and grain coarseness appear in the transition zone;comb tooth of permeation layer of 45 steel is thicker and denser than 20 steel. Boron-vanadizing improves density of permeation layer.All the boriding layers obtain Fe₂B and FeB phase.Content of FeB phase in boriding layer decrease with the increase of sample carbon content.boron-vanadizing is inclined to inhibit FeB phase,and is likely to engender V₂C and VB phase.Microhardness of boron-vanadizing layer is higher than boriding layer,but its hardness gradient is rather big.Microhardness of RE-boron-vanadizing layer decreases for the influence of ihrigizing,and its hardness gradient is less. Brittleness of 20 steel is higher than 45 steel markedly under heavy load,brittleness of RE-boron-vanadizing layer and boron-vanadizing layer is higher than boriding layer, thereforce the boronized samples by multicomponent thermochemical Treatment should be quenched and tempered for the purpose of enhance body intensity.Finally, nucleation and growth model of the layers ,Microscopic diffusion Mechanism of the elements and effects on properties of the layers are discussed on the basis of the results of the experiments.更多还原