摘要：对Cr12和Cr12MoV两种Cr12型冷作模具钢进行固体渗硼，渗硼温度为880℃、910℃、940℃和970℃，保温时间为3h、5h、7h和9h；用光学显微镜观察渗层显微组织，根据渗层厚度和时间的关系计算得到生长速率常数k和扩散激活能Q；用显微硬度计测量了渗层硬度梯度；用X射线衍射仪对渗层进行相分析，确定渗层表面的物质组成；根据渗硼温度和时间，使用Sigma软件绘制渗层等厚度图。结果表明，Cr12钢渗层厚度在15-122μm之间，硬度最高可达1855 HV0.1，渗硼扩散激活能Q为185.65kJ/ mol; 而Cr12MoV钢渗硼后的渗层厚度在13-112μm之间，硬度最高可达1931 HV0.1，扩散激活能Q为192.65 kJ/ mol。对比两种钢的渗硼结果可知，渗层表面主要相均为硬且脆的FeB相；然而，由于合金元素含量的差别，Cr12MoV钢渗硼相对较难，虽然深层硬度稍高，但脆性大，容易出现裂纹；而且渗层孔洞多，致密度下降。另外，等厚度图的绘制，将温度、时间、渗层厚度联系起来，为以后的实践提供理论依据。61095

毕业论文关键词：Cr12  渗硼层  动力学  激活能

毕业设计说明书（论文）外文摘要

Title    Research  on  the  Boronizing  Process of Cr12 Type Cold Work Die Steels

Abstract In this study, the Cr12,Cr12MoV cold work die steels substrates were pack-borided at 880, 910, 940 and 970℃ for 3, 5, 7, and 9 h. The morphology and thickness of borides formed on the surface of steel substrates were confirmed by optical microscopy analysis, depending on which activation energies were figured out. The hardness gradients of boride layers formed on the samples were measured by using micro -hardness tester. The phases were confirmed by X-diffraction method to determine what the boriding layers were composed of. According to process temperature, treatment time and boride layer thickness, the contour diagrams of boride layers were drawn out. The results showed that the boride layer thickness formed on the borided Cr12 and Cr12MoV steels range from 15 to 122μm and from 13 to 112μm ,respectively. Activation energies (Q) of borided Cr12 and Cr12MoV steels at present study are determined as 185.65 and 192.65KJ/mol, respectively. The max-microhardness of boriding layers of borided Cr12 and Cr12MoV steels could reach 1855 and 1931HV0.1,respectively. Comparing the boriding results of Cr12 steels with those of Cr12MoV steels , these conclusions are made that the major phase of these boriding layers is FeB which is very hard and brittle. However, on account of different contents of alloying elements, It’s more difficult for Cr12MoV steels to boronize; Compared to borided Cr12 steels, the boride layers of Cr12MoV steels which include small holes leading to reduced density , are more brittle and prone to crack, despite their hardness are slightly higher. Moreover, by linking process temperature, treatment time and boride layer thickness, the contour diagrams are figured out to provide a theoretical basis for future practice.

Key words: Cr12 type cold work die steel; Boride layer; Kinetics; Activation energy

1 绪论 1

1.1 Cr12型冷作模具钢简介. 1

1.2 Cr12型冷作模具钢的渗硼研究. 2

1.3 渗硼动力学.. 4

1.4 本课题主要研究内容及意义.. 6

2 实验方法 6

2.1 实验材料..6

2.2 渗硼剂组成..6

2.3 实验设备..6

2.4 实验过程与方法..7

3 实验结果与讨论 8

  3.1 Cr12、Cr12MoV钢渗硼层的金相组织分析..8

  3.2 Cr12、Cr12MoV钢渗硼层的显微硬度分析..11

  3.3 Cr12、Cr12MoV钢渗硼层的XRD分析11

  3.4 Cr12、Cr12MoV钢渗硼动力学.14