Thixocasting Steel Hand Tools using Al2O3-coated Steel and Molybdenum Dies

• Published in: Steel research international Vol. 81; no. 7; pp. 581 - 588
• Main Authors: Bünck, M., Subasic, E., Bührig-Polaczek, A., Jiang, K., Münstermann, S., Schneider, J. M., Fickert, K., Günther, H.-J.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.07.2010; WILEY‐VCH Verlag
• Subjects: Austenitic stainless steels; Casting; Chemical vapor deposition; Forging; Hand tools; Ion nitriding; Iron and steel industry; Molybdenum base alloys; Semi-solid; Semi-solid processing; Thixocasting; Tool steels; X39CrMo17 steel
• ISSN: 1611-3683; 1869-344X; 1869-344X
• DOI: 10.1002/srin.201000032

Forging is state‐of‐the‐art for producing hand tools on an industrial scale. Due to high demands on the stiffness and the fracture toughness, high‐strength forging steels are used to provide cavity‐free components with high mechanical load capacity. Moreover, forging is a cost‐effective mass production process but, in spite of all its advantages, it has its limitations, e.g. in the freedom of designs. However, because of the extreme thermal loading (particularly with regard to permanent moulds) and the frequently unavoidable casting defects, hand tools are not cast. By means of thixocasting steel, technical difficulties can be reduced and new options are provided which allow the manufacturing of components with much higher complexity than that using forging. Through near‐net shape production, manufacturing steps and costs can be reduced. Furthermore, steels, which are difficult to forge but nonetheless have high potential for specific applications (such as high strength or corrosion resistant steels), can also be processed. In cooperation with industrial partners, X39CrMo17 stainless steel size 17 combination spanners were thixocast. Forming dies were designed and optimized by simulation, the hot forming X38CrMoV5 tool steel as well as the molybdenum alloy TZM were selected as the tool alloys. The dies were treated by a plasma nitriding process and subsequently coated with crystalline Al2O3 protective coatings by plasma‐enhanced chemical vapor deposition (PECVD). During the experiments, combination spanners were successfully cast in the semi‐solid state. Cast parts were heat‐treated to enhance the components' toughness, which was subsequently measured by Charpy impact and tensile tests.