Laser-powder bed fusion (LPBF) is one of the preferred techniques for producing Co-Cr metal structures for dental prosthodontic appliances. However, there is generally insufficient information about material properties related to the production process and parameters. This study was conducted on samples produced from three different commercially available Co-Cr dental alloys produced on three different LPBF machines. Identically prepared samples were used for tensile, three-point bending, and toughness tests. Light microscopy (LM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) analyses of microstructure were performed after testing. Differences were observed in microstructures, which reflected statistically significant differences in mechanical properties (one-way analysis of variance (ANOVA) and Scheffé post hoc test (α = 0.05)). The material produced on the 3D Systems DMP Dental 100 had 24 times greater elongation ε than the material produced on the Sysma MySint 100 device and the EOS M100 machine. On the other hand, the material produced on the EOS M100 had significantly higher hardness (HV0.2) than the other two produced materials. However, the microstructure of the Sysma specimens with its morphology deviates considerably from the studied group. LPBF-prepared Co-Cr dental alloys demonstrated significant differences in their microstructures and, consequently, mechanical properties.

Effects of such thermochemical processes as carburising, nitriding and boriding on properties of maraging steel grades have been investigated. Despite certain improvements in the properties of the obtained surface, at present, carburising and boriding cannot be recommended owing to problems in the layer quality and difficulties in dimension control processes. Nitriding has proved to be the most suitable process and subsequent surfacing with a TiN layer on the previously nitrided substratum of maraging steel provided additional improvement in properties.

Charpy V-notch (CVN) impact test values are widely used in toughness specifications for spring steels, even though the fracturing energy is not directly related to the spring's design. Both standard and non-standard methods for determining KIc are expensive and time consuming. In this paper, based on the results of experimental studies on spring steel grade 51CrV4, we have tried to find an expression so as to determine the fracture toughness from a computation based on the test results of the CVN and the Rockwell C hardness. This would be a much more economical and faster way to evaluate the fracture toughness of spring steels.

Deep cryogenic treatment in combination with classic heat treatment shows a significant improvement in wear resistance of high speed steel tools. The aim of this research was to investigate how the microstructure of the substrate tool steel material, which was altered by deep cryogenic treatment and plasma nitriding, influences the properties of TiAlN coating. The microstructure, topography and composition of the TiAlN coating were investigated using field-emission scanning electron microscope, atomic force microscopy, XRD, and glow discharge optical emission spectroscopy. The coating adhesion was measured using the scratch test. The sliding wear resistance and the force required to break the coating were determined with the ball-on-flat method. Resistance to microabrasion was measured by free ball abrasion test. The results show that deep cryogenic treatment combined with plasma nitriding influence the adhesion of the TiAlN coating to the high speed steel substrate. Wear resistance tests show better wear resistance of deep cryogenic treated samples in comparison with conventionally heat treated ones.Keywords: deep cryogenic treatment / plasma nitriding / PVD TiAlN coating / abrasive wear resistance / Die kryogenische Behandlung in Kombination mit der klassischen Behandlung zeigt eine wesentliche Verbesserung der Verschleißfestigkeit von Hochgeschwindigkeits-Werkzeugen an. Das Ziel dieser Arbeit war die Untersuchung der Mikrostrukturauswirkung des Werkzeugstahlsubstrats, das mit der kryogenischen Behandlung und mit dem Plasmanitrieren modifiziert wurde, auf die Eigenschaften der TiAlN Beschichtung zu zeigen. Die Mikrostruktur, die Topographie und die Zusammensetzung der TiAlN Beschichtung wurde mit FE, SEM, atomic force microscopy, XRD und glow discharge optical emission spectroscopy untersucht und analysiert. Die quantitative Beurteilung der Beschichtungsadhäsion wurde mit der Ritzprüfung durchgeführt. Der Gleitverschleiß und die benötigte Kraft mit der man die Beschichtung zerstören kann, waren mit der "Ball-on-Flat" Methode geprüft. Der Mikroabrasionswiderstand wurde mit dem Kalottenschliffverfahren gemessen. Die Resultate zeigen, dass die kryogenische Behandlung in Kombination mit dem Plasmanitrieren einen Einfluss auf die Adhäsion der TiAlN Beschichtungen an dem Hochgeschwindigkeits-Substrat hat. Die Gleitverschleißprüfungen zeigen bessere Resultate der kryogenisch behandelten Proben gegenüber den konventionell behandelten Proben.Schlüsselwörter: kryogenische Behandlung / Plasmanitrieren / PVD TiAlN Beschichtung / Charakterisierung / Gleitverschleißwiederstand /

Application of deep cryogenic treatment instead of conventional heat treatment showed an increase in wear resistance of tools made of high speed steel which are exposed to very complex and demanding conditions in exploitation. The purpose of this study was to investigate the effect of deep cryogenic treatment in combination with plasma nitriding on the tribological properties of powder metallurgy high speed steel, grade PM S390 MC. On treated specimens hardness and fracture toughness was determined, the resistance to intensive adhesive wear (galling) and dry sliding wear (dry sliding wear resistance) were also tested. Test results show that deep cryogenic treatment in combination with plasma nitdriding contributes to better abrasive wear resistance and better galling properties of tested powder metallurgy high speed steel.