In-situ investigations of the physicochemical mechanisms of surface activation of stainless steels during heat treatment applying brazing-process-like conditions in reducing process gases

在还原工艺气体中应用类似钎焊工艺的条件进行热处理期间不锈钢表面活化的物理化学机制的原位研究

• 批准号: 268192580
• 负责人: Professor Dr. Ronald Reinhard Frahm
• 金额: --
• 依托单位: Institut für Werkstoffkunde (IW)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/268192580?language=en
• 关键词: situ; investigations; physicochemical; mechanisms; surface

The deoxidation of work piece surfaces in a furnace brazing process using reducing process gases is the pre-condition for its wettability with braze metal and determines the success and the quality of the resulting brazed joints. While the necessary thermodynamic conditions for the reduction of native oxidized stainless steel surfaces with hydrogen or monosilane are known, the kinetics of such reactions has not been investigated up to now on the atomic scale. However, the latter is essential for a general understanding of the process and is key for further developments in brazing technology. In this context, the use of monosilane doped nitrogen as a cost efficient and resource saving alternative to hydrogen, which is state of the art in furnace brazing, is of mayor scientific and technologic interest.The proposed research aims at developing a fundamental understanding of the physicochemical mechanism of surface deoxidation, when brazing stainless steels in a conveyor belt furnace using hydrogen and monosilane containing process gases. The experiments planned are expected to provide detailed information of the chemical reactions and surface conditions during brazing, which are essential for the advancement of fluxless brazing processes with regard to lower process temperatures, robust processes and demanding stainless steel specifications.The starting point of the project are thermodynamic calculations of possible reactions, for which analytical transport models of oxide layer formation are specified and adjusted for the actual problem. These theoretical considerations are validated by in situ analysis of surface reactions - also time resolved - covering typical process conditions in a conveyor belt furnace, in order to obtain information about the kinetics of changes in the surface region of stainless steels with respect to crystal structure, atomic coordination (bond distances, coordination numbers), chemical bonding and atomic diffusion. For this purpose TR-XRD (Time Resolved X-ray Diffraction) and X-ray absorption spectroscopy (EXAFS/XANES) measurements using synchrotron radiation are performed. Realistic furnace conditions during these measurements will be realized in a high temperature cell for X-ray experiments, which is custom-made to be able to mimic the conditions in the actual brazing process.The X-ray measurements are performed at the DELTA synchrotron light source in Dortmund, which is located close to the home institutions of the applicants, and the working group of Prof. Frahm operates two X-ray beamlines there. Additional experiments are planned at the Synchrotron Radiation Facilities SLS, SOLEIL and ESRF.Based on the diffraction data obtained and complementary brazing experiments in a conveyor belt furnace with ex-situ analysis of the heat treated specimen a physical model will be developed, which takes into account the relevant physicochemical aspects of surface changes in brazing processes.

在使用还原性工艺气体的炉内钎焊工艺中，工件表面的脱氧是其与钎焊金属润湿的先决条件，并决定了所得钎焊接头的成功和质量。虽然用氢或甲硅烷还原天然氧化不锈钢表面的必要热力学条件是已知的，但迄今为止尚未在原子尺度上研究这种反应的动力学。然而，后者对于一般理解该工艺至关重要，并且是钎焊技术进一步发展的关键。在这种情况下，使用甲硅烷掺杂的氮作为一种具有成本效益和资源节约的替代氢，这是最先进的炉钎焊，是市长的科学和技术interests.The拟议的研究旨在发展的物理化学机制的基本理解，表面脱氧时，钎焊不锈钢在传送带炉使用氢和甲硅烷的工艺气体。计划中的实验预计将提供钎焊过程中化学反应和表面条件的详细信息，这对于在较低工艺温度、稳健工艺和苛刻的不锈钢规格方面推进无焊剂钎焊工艺至关重要。该项目的起点是对可能的反应进行热力学计算，其中氧化物层形成的分析传输模型被指定并针对实际问题进行调整。这些理论考虑通过表面反应的原位分析（也是时间分辨的）来验证，涵盖传送带炉中的典型工艺条件，以便获得有关不锈钢表面区域在晶体结构、原子方面变化动力学的信息。配位（键距、配位数）、化学键和原子扩散。为此，使用同步辐射进行TR-XRD（时间分辨X射线衍射）和X射线吸收光谱（EXAFS/XANES）测量。这些测量过程中的真实炉况将在用于X射线实验的高温室中实现，该高温室是定制的，能够模拟实际钎焊过程中的条件。X射线测量在多特蒙德的DELTA同步加速器光源处进行，该光源靠近申请人的家庭机构，Frahm教授的工作组在那里操作两条X射线光束线。计划在同步辐射设施SLS，SOLEIL和ESRF.Based上获得的衍射数据和互补的钎焊实验在传送带炉与非原位分析的热处理试样的物理模型将开发，考虑到在钎焊过程中的表面变化的相关物理化学方面。

项目成果

Brazing in SiH4-Doped Inert Gases: A New Approach to an Environment Friendly Production Process

• DOI: 10.1007/s40684-019-00109-1
• 发表时间: 2020-11-01
• 期刊: INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING-GREEN TECHNOLOGY
• 影响因子: 4.2
• 作者: Hollaender, Ulrich;Wulff, Daniel;Maier, Hans Juergen
• 通讯作者: Maier, Hans Juergen

Ex-situ and in-situ investigations of thermal anti-oxidation treatments of stainless steels by reflection mode EXAFS

反射模式 EXAFS 不锈钢热抗氧化处理的异位和原位研究

• DOI: 10.1088/1742-6596/712/1/012047
• 发表时间: 2016
• 期刊: Journal of Physics: Conference Series
• 作者: Lützenkirchen-Hecht;Wagner;Holländer
• 通讯作者: Holländer