B-alloyed tool steels - thermodynamic calculation and metallographic characterization of the effect of the alloying elements Mn and Mo in the quaternary system Fe-C-B-Cr

B合金工具钢。四元系Fe-C-B-Cr中合金元素Mn和Mo影响的热力学计算和金相表征

基本信息

批准号：
232707733
负责人：
Professor Dr.-Ing. Arne Röttger
金额：
--
依托单位：
Lehrstuhl für Neue Fertigungstechnologien und Werkstoffe (FUW)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2012
资助国家：
德国
起止时间：
2011-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/232707733?language=en
关键词：
alloyed tool steels thermodynamic calculation

项目摘要

As a hard-phase forming alloying element, boron is a cost-effective possibility to improve the tribological performance of tool steels. Targeted stabilization of boride phases is used to uncouple martensitic hardening (promoted by carbon) from hard phase formation. In particular, borides of M2B type (Fe2B, Cr2B, (Fe,Cr)2B) feature higher hardness and fracture toughness than the carbide of type M7C3. These Cr-rich M7C3 carbides are used as hard phase in conventional tool steel concepts. Results gathered in the first funding period show that high B/(B+C)-ratios promote the formation of M2B type borides. In addition, the alloying element Cr further stabilizes the M2B phase and improves its micro-mechanical properties like hardness and fracture toughness. With respect to the solidification sequence in the system Fe-C-B and Fe-Cr-C-B, carboborides of M3(C,B) or M23(C,B)6 type are formed besides the M2B type boride. The formation of these softer carboborides is associated by a consumption of the elements C and Cr. This counteracts a martentisic hardenability of the metal matrix by C depletion and decreases the hardness of M2B phase due to decreased solute Cr-content inside the M2B phase. Preliminary test as well as literature data indicate that the elements Mn and Mo further stabilize the M2B type phase, while avoiding the formation of undesirable carboborides in the systems Fe-C-B and Fe-Cr-C-B.However, characterization and understanding of the effects of the alloying elements Mo and Mn in the systems Fe-C-B and Fe-Cr-C-B remains an area of research interest. Regarding the development of tool steels, focus of the investigations is placed on solidification sequence, resulting microstructure and phase composition, phase transformation in solid-state and micro-mechanical properties of the formed hard phases. Within the scope of the renewal proposal, thermodynamic calculation and metallographic characterization of laboratory melts are simultaneously used to uncover the interdependencies of the elements Cr and Mn or Mo in the underlying mechanisms. Furthermore, the effect of the element B on secondary-hardening precipitations is of high interest. Commonly, secondary-hardening carbides are formed by the alloying elements Mo, Cr, V and C during tempering a quenched tool steel in the secondary hardening regime. It will be investigated, whether the low solubility of boron and its simultaneously high diffusivity in the metal matrix enable the formation of secondary-hardening borides or carboborides. Results will be used to deduce an alloying concept for a B-alloyed tool steel. Using this concept, an alloy featuring preferably spherolitic M2B borides, which are embedded inside a martensitic metal matrix should be developed. Finally, tribological properties of this alloy are characterized to enable comparability with a conventional Fe-Cr-C based reference alloy.

作为形成合金元素的硬相，硼是改善工具钢的摩擦学性能的一种经济高效的可能性。靶向硼化物相的稳定稳定用于从硬相形成中解开马塞塞我的硬质硬化（由碳促进）。特别是，M2B类型的硼化物（FE2B，CR2B，（Fe，Cr）2b）比M7C3型碳化物具有更高的硬度和断裂韧性。这些富含CR的M7C3碳化物在常规工具钢概念中用作硬相。在第一个资金期间收集的结果表明，高B/（B+C） - 鼠标促进了M2B型硼化物的形成。此外，合金元件CR进一步稳定了M2B相，并提高了其微力学特性，例如硬度和断裂韧性。关于系统Fe-C-B和Fe-Cr-C-B中的凝固序列，M3（C，B）或M23（C，B）6类型的Carboborides除M2B型硼化物外还形成。这些柔软的碳纤维形成与元素C和Cr的消费相关联。这抵消了金属基质通过C耗竭的马嫩素强度，并降低了M2B相中M2B相中溶质cr的硬度的硬度。初步测试以及文献数据表明，MN和MO进一步稳定了M2B类型阶段，同时避免了系统Fe-c-c-b和fe-cCR-c-b和fe-cr-c-b的形成，对系统Fe-c-b-b和fe-c-b-b研究的效果的表征和理解仍然是Fe-c-b-b和fe-cr-c-b。关于工具钢的开发，研究的重点放在凝固序列上，导致微结构和相组成，固态和微力学特性的相变。在更新建议的范围内，实验室熔体的热力学计算和金相表征同时用于揭示基本机制中元素CR和MN或MO的相互依赖性。此外，元素B对二次硬化降水的作用引起了人们的兴趣。通常，在次要硬化状态下的淬火工具钢中，合金元素，CR，V和C的合金元素MO，CR，V和C形成了次要硬化碳化物。将研究硼的低溶解度及其在金属基质中同时具有很高的扩散率是否能够形成次级硬化的硼化物或碳纤维。结果将用于推断出与B合金工具钢的合金概念。使用此概念，应开发出嵌入在马氏体金属基质中的球状M2B硼的合金。最后，该合金的摩擦学特性具有与常规的基于FE-CR-C的参考合金的可比性。