Sanja Šolić

Fracture toughness-Charpy impact test- Rockwell hardness regression based model for 51CrV4 spring steel

Abstract 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.

Effect of deep cryogenic treatment on mechanical and tribological properties of PM S390 MC high-speed steel

Abstract 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.

Effects of thermochemical treatments on properties of maraging steels

Abstract 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.

Influence of heat treatment on mechanical properties of 51CrV4 high strength spring steel

The durability of the springs is limited by plastic deformation, fatigue and fracturing. From this point of view, the use of spring steel with following properties is recommended: high ductility and toughness at operation temperatures from −40°C to +50°C, good hardenability that provides required mechanical properties even at maximum dimensions. For the manufacturers of springs, the information relating to the heat treatment of specific spring steel is important. This paper describes the influence of heat treatment parameters on tensile strength Rm, yield strength Rp0·2, fracture toughness KIc, impact toughness, Charpy-V as a function of tempering temperature in the range from 350 to 700°C for a specific austenitising temperature. Also the difference between the properties given by the mathematical modelling of heat treatment using the computer software Hardenability and the properties obtained by testing the heat treated samples are presented.

Effect of deep cryogenic treatment on dilatometric curve and tribological properties of high speed steel

Advantages of deep cryogenic treatment (DCT) over the standard heat treatment of high speed steels for the purpose of obtaining better properties are quoted in an increasing number of scientific papers to be found in literature. This paper deals with the improvements in high speed steel properties achieved by using DCT on test samples made of PM S390 MC high speed steel. The effect of DCT on the dilatometric curve during tempering and on the abrasive and the erosion wear resistance has been investigated and compared with results obtained from a set of test samples made of the same steel heat treated by the conventional method (hardened and three times high temperature tempered). Dilatometric tests confirmed the existence of common processes in tempering, which depend on the initial state of steel (only quenched, and quenched and deep cryogenically treated). These tests showed that the DCT had not completely eliminated the residual austenite, particularly in the case of the highest austenisation temperatur...