Influence of Vacuum Heat Treatments on Microstructure and Mechanical Properties of M35 High Speed Steel

Abstract

Towards the end of the last century, vacuum heat treatment of high speed steels was increasingly used in the fabrication of precision cutting tools. This study investigates the influence of vacuum heat treatments at different pressures of quenching gas on the microstructure and mechanical properties of taps made of M35 high speed steel. Taps were characterized by optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, apparent grain size and Vickers hardness measurements, and scratch tests. Failure analysis after tapping tests was also performed to determine the main fracture mechanisms. For all taps, the results showed that microstructures and the values of characteristics of secondary carbides, retained austenite, apparent grain size and Vickers hardness were comparable to previously reported ones for vacuum heat treated high speed steels. For taps vacuum heat treated at six bar, the highest plane strain fracture toughness was due to a higher content of finer small secondary carbides. In contrast, the lowest plane strain fracture toughness of taps vacuum heat treated at eight bar may be due to an excessive amount of finer small secondary carbides, which may provide a preferential path for crack propagation. Finally, the predominant fracture mechanism of taps was quasi-cleavage.

Study on the Tribological Behavior of Wear and Friction Coefficient on AISI M35 High-Speed Steel with and without DLC Coating

“…Table 1 shows the measured chemical composition. The result of this analysis was compared with the chemical composition found by other authors who studied the same material [24][25][26] , in addition to the ASTM A600 -Standard Specification for High Speed Steel Tools (Figure 2). The microstructure of the HSS was analyzed using scanning electron microscopy (SEM) on the TESCAN VEGA 3 equipment, equipped with array of tungsten filament, 300 nm resolution at 30 kV and 8 nm resolution at 3kV, with secondary electrons (SE) and scattered electrons (BSE), magnification of 2X-1,000.00X and electron beam energy from 2eV to 30kV.…”

“…The more refined precipitates have elliptical and globular morphology. In the analysis by 24 on AISI M35 HSS, carbides of different sizes were also identified. The primary carbides, formed after quenching, were rich in vanadium, molybdenum and tungsten with coarse morphology and distributed heterogeneously.…”

Tribological properties of high-entropy high-speed steels under conditions of friction on stainless steel 12H18N9T

“…Currently, the performance characteristics of tools made of high-speed steels (HSS) are increased by chemical-thermal treatment, deposition of coatings, laser hardening methods and other methods related to the modification of the surface or volume properties of the material, as well as through the development of new grades of HSS [1][2][3][4][5]. The ability to predict a priori some operational characteristics of experimental compositions of tool cutting materials (TCM) is provided by the study of thermodynamic aspects of processes of wear during friction (cutting).…”

Automatic Method for Vickers Hardness Estimation by Image Processing

“…Materials such as steel used in automotive axles, cutting tools, among other applications, are subjected to constant forces or loads, which can cause deformation or breakage of the material. The search for continuous improvement has led to the implementation of materials in the form of thin films, which consist of improving the surface properties of the substrate such as steel, providing high hardness, low coefficient of friction, and wear and corrosion resistance in chemically aggressive environments, allowing for increasing its useful life and covering a wide field of applications [ 8 , 9 , 10 , 11 , 12 ].…”

“…There are different methods to modify the hardness of the material, either by heat treatment such as quenching or tempering to modify the microstructure [ 11 , 12 ] or by depositing thin film coatings on the surface of the base material. Among the most commonly used coatings in the industry are Titanium Nitride (TiN) and Niobium Nitride (NbN).…”