Physico-chemical study of high speed steel structural components

This paper is a study concerning structural components of high speed steels. The purpose of this study is the characterisation of the high speed steels structural components by several physico-chemical methods, the correlation of the main features and the improvement of the properties of these steels by heat treatment. One study is of the carbide phases: type M2C, M6C, MC or type Fe-W-C, Fe-Mo-C, using metallographic methods and the matrix features in correlation with the chemical composition. The structural components have been distinguished by specific etchings, followed by optical microscopy. The heat treatment of the high speed steels and the features of structural components: martensite, austenite, primary and secondary carbides have also been studied. X-ray diffraction has been used to determine the retained austenite fraction (10-15%) after heat treatment and mean crystallite sizes (D = 571.71A and 571.91Å), which are related to the solidification pattern. An unwelcome structural feature of high speedsteel is the decarburization. It has been determined as a non-homogeneous decarburate layer 1mm, which is correlated to HRC hardness (HRC = 52-54). The study has been applied to characterise some cutting tools made of high speed steels and Rp5 high speed steel used for the pin nozzle, which equips the body nozzle of the diesel injection components.