Franjo Cajner

Effect of Deep-Cryogenic Treatment on High Speed Steel Properties

Advantages of deep-cryogenic treatment over standard heat treatment of high speed steels for the purpose of obtaining better properties are quoted in an increasing number of scientific articles. This article deals with the most important improvements of high speed steel properties achieved by using deep-cryogenic treatment. The effect of deep-cryogenic treatment on impact and fracture toughness, on erosion wear resistance, and on the material microstructure has been tested on samples made of the PM S390 MC high speed steel. A set of test samples was heat treated by conventional methods (hardened and three times high temperature tempered), and the other set was deep cryogenic treated. From the results, it can be concluded that the application of deep-cryogenic treatment results in significantly higher wear resistance of high speed steels, but no significant improvements in toughness have been observed.

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 Austempering on Fracture Mechanics Parameters of 65 Si 7 Steel

The aim of the performed investigations was to determine the influence of two different heat treatment procedures, i. e. hardening and tempering vs. austempering, on some mechanical and fracture properties of a particular type of steel. An advantage of austempering over hardening and tempering is in obtaining the bainite microstructure which has greater toughness, strain, contraction, fatigue strength and a better fracture toughness than a tempered martensite of the same type of steel [2,3]. All these advantages of bainite refer to untempered state. By tempering of bainite microstructure steel its toughness decreases and in tempered bainite it is lower than the toughness of temepered martensite [3].

An analysis of induction hardening of ferritic ductile iron

Achievements of the induction hardening of ferritic ductile iron were investigated. Ductile iron is not advisable for use in induction hardening because of the small carbon content in the metal matrix of ferritic ductile iron. The carbon content in the metal matrix of ductile iron can be increased by additional preparation of metal matrix before final induction heat hardening. Wear resistance of the induction hardened ferritic ductile iron can increase as result of increased carbon content of the metal matrix and higher hardness after induction hardening. Some heat pretreatments for metal matrix preparation were applied before the induction hardening of ferritic ductile iron. The process parameters of the induction hardening heat pretreatment were analyzed and optimized. According to recommended elemental composition of ferritic ductile iron and required mechanical properties, the process parameters of the investigated induction heat pretreatment were optimized. The efficiency of pretreatment processes of induction hardening was analyzed. Applicability and manufacture ability of engineering components by proposed heat pretreatments were investigated. The limitations of the investigated heat pretreatment applications were estimated by the comparison of mechanical properties of heat-treated specimens.

Influence of Steel Substrate on the Properties of PACVD Gradient Multilayer TiCN Coating

Titanium-based hard coatings are known for increasing both hot work and cold work tool steel performance in terms of wear and corrosion resistance. In this paper, the influence of different steel substrates on the properties of plasma-assisted chemical vapor deposition (PACVD) gradient multilayer titanium carbo-nitride (TiCN) coating was investigated. The same gradient multilayer TiCN coating was deposited by pulsed direct current (dc) PACVD on a hot work tool steel grade X37CrMoV5-1 and two Bohler cold work tool steels K390 PM and K110. Hardened samples of each steel were also included in the investigation. The coating-substrate systems have been characterized with respect to their chemical composition, thickness, adhesion, and resistance to electrochemical corrosion, abrasion, erosion, and dry sliding wear. The results show an increased wear and corrosion resistance of TiCN-coated specimens compared with noncoated and prehardened specimens. The application of gradient multilayer TiCN coating on different steel substrates shows the different behavior of TiCN coating. Therefore, besides the coating itself, the base material on which the coating is applied has a significant influence on the tool properties.

Influence of heat treatment of high-speed steel on its microstructure, hardness and fracture toughness

The correlation between fracture toughness, hardness and microstructure of vacuum heat-treated high-speed steel AISI M2 was investigated. Our intention was to investigate the influence of microstructural parameters such as the volume fraction of undissolved eutectic carbides, their mean diameter, the mean distance between the carbides, as well as the volume fraction of retained austenite in the matrix, on the above mentioned mechanical and fracture properties. The experimental investigations were performed on the high-speed steel. This steel had the following chemical composition (mass content in %): 0.89% C, 0.20% Si, 0.26% Mn, 0.027% P, 0.001% S, 3.91% Cr, 4.74% Mo, 1.74% V and 6.10% W.

Influence of Heat Treatment on Crack Tip Opening Displacement and on Resistance of Crack Propagation of Alloyed Steel

The aim of the performed investigations was to determine the influence of two different heat treatment procedures, i.e. hardening and tempering vs. austempering, on some mechanical properties, as well as the influence of these procedures on the magnitude of some fracture mechanics parameters for example, crack tip opening displacement (CTOD) and J-integral. The experimental investigations were performed on the specimens made of spring steel 65Si7 (chemical composition: 0.69% C, 1.56% Si and 0.90% Mn).

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...

Effect of the heating rate in the tempering of DIN 100 V1

Abstract In this paper, the effect of the heating rate on the process of tempering and the obtained hardness of the DIN 100 V1 (AISI W2) carbon tool steel has been investigated and determined. Steel specimens in two initial states were investigated: after quenching and after quenching and deep-cryogenic cooling. The specimens were submitted to tempering in a dilatometer, varying the heating rates, temperature of tempering between 200°C and 690°C and duration of keeping the specimens at that temperature. A common effect of these factors on the temperature of the start of particular stages in tempering and the obtained properties was determined using dilatometry. Differential dilatation analysis was carried out, together with hardness tests and XRD (X-ray diffraction) analysis.