Dilatometric analysis tool steel X153CrMoV12

The article deals with phase transformations and austenitizing behavior of the X155CrMoV12 tool steel. Dilatation analyses of a series of samples were performed at various cooling rates, chosen in the range from 10 °C·s-1 to 0.1 °C·s-1. Acquired experimental data were used for evaluation of dilatometric curves in order to map the temperature ranges of phase transformations of the austenite to pearlite, bainite or martensite. All experimental samples from dilatometric analyses were then subjected to microstructural analyses and hardness measurements to characterize the microstructure and hardness for every tested heat treatment regime. The second part of this article, entitled "EXPERIMENTAL DETERMINATION OF CONTINUOUS COOLING TRANSFORMATION DIAGRAM FOR HIGH STRENGTH STEEL X153CRMOV12", deals with these analyses of the cooling curve microstructure.

Optimization of heat treatment of glass-ceramics made from blast furnace slag

CaO–MgO–Al2O3–SiO2 glass-ceramics with diopside as the main crystalline phase were prepared by melting blast furnace slag obtained from Baotou Iron and Steel Company. The effect of heat treatment on the crystallization behavior of glass-ceramics, containing a large proportion of melted blast furnace slag, was studied by means of differential thermal analysis and scanning electron microscopy. The optimum heat-treatment regime was obtained by orthogonal experimental results for glass-ceramics in which blast furnace slag comprised 70% of the composition and 1% Cr2O3 and 4% TiO2 were used as nucleating agents. The nucleation temperature was 750°C for 2.5 h and the crystallization temperature was 930°C for 1 h. Under this regime, the performance of the glass-ceramic was better than that of other groups in the orthogonal experiment.

Control Factors on the Heat Treatment Process Applied to A537 Steel for Increasing Hardness Using Hardening and Tempering

The paper is based on laboratory experiments of heat treatments applied to samples of A537/A537M steel. The work continues other previous works aimed at modifying structures and properties of this steel, including through surface treatments. The experiments were performed using Taguchi methods from Quality Engineering. A number of four factors were selected as influencing the structure after heat treatment: heating temperature for hardening, cooling rate on hardening, time and tempering temperature. A number of nine experiments were performed using an L9 orthogonal matrix. Objective function was changed to maximum hardness after the heat treatment regime. The results show that the tempering temperature has the greatest influence on the final hardness of the A537 steel samples.

Choosing a Suitable Heat Treatment Regime for Stress-Relief and Microstructure Stabilization of Ti6Al4V Alloy 3D-printed by SLM Method

During the processing of Ti6Al4V alloy by a 3D printing method SLM (selective laser melting), high internal stresses are developed in the material as a result of high temperature gradients between microvolumes of the powder melted at a given time and the already solidified material. Cooling rates thus reach up to the order of 108 °C·s-1. At such rates, a diffusionless martensitic transformation occurs, which also contributes to internal stresses in the material. High internal stresses can be a problem already during production; they can manifest themselves by cracking of products, deformations of thin parts, etc. Even in defectless products, internal stresses negatively affect their properties; in particular, they reduce ductility. Therefore, it is desirable to include a heat treatment after the 3D printing, which would reduce the stresses and transform the metastable martensitic structure into a stable one. As a result of the heat treatment, the ductility increases at the expense of strength. The subject of this paper is to find such heat treatment regime that provides the best combination of mechanical properties.

Evaluation of the Cavitation Resistance of INCONEL 718, in Delivered and Respectively Heat Treated Condition

Inconel 718 is a very difficult metal for machining because of its high plasticity. Lately, more and more researchers are interested in using it for cavitation parts, such as the plugs and drawers of the valves. For this purpose, thermal volumetric treatments have been initiated to facilitate mechanical machining, aiming simultaneously to obtain good compression and cavitation resistance results. Therefore, this paper presents the results of cavitation erosion behavior and cavitation resistance of ICONEL 718, subjected to two thermal treatment regimes, differentiated by the duration (temperature 800 °C and residence times 5 hours, and respectively 10 hours). The assessment of the cavitation resistance provided by each heat treatment regime is based on the average durability cavitation parameter, as defined by K. Steller. The research is achieved by using the standard vibrator device with piezo - ceramic crystals from the Cavitation Laboratory of the Politechnica University of Timisoara.

Assessment of the Cavitation Resistance of Stainless Steel X5crni18-10, Subjected to Thermal Sensitization Based on Average Durability

Among the uses of stainless steel GX5CrNi18-10 one mentions the hydraulic machine blades and the rotors, which are highly susceptible to cavitation. To achieve a long life service under cavitation conditions, the pieces made of this steel are subjected to volumetric thermal treatments, which change the structure and mechanical properties. In this paper, one presents the results of the research concerning the behavior and the resistance to the cavitation erosion of the thermally sensitized GX5CrNi18-10 stainless steel, applying four different temperature regimes (two at 650°C and two at 750°C) and different durations (30 minutes and respectively 60 minutes). The results are presented in the form of cumulative mass loss curves M (t) and erosion rate v (t). The assessment of the cavitation resistance provided by each heat treatment regime is based on the average durability cavitation parameter, as defined by K. Steller. The research was conducted on the standard vibrator with piezo-ceramic crystals from the Cavitation Laboratory of the Politechnica University of Timisoara.

Hydrogen Effect on Cumulation of Failure, Mechanical Properties, and Fracture Toughness of Ni-Cr Alloys

Influence of hydrogen pressure and internal hydrogen contents on short-term strength, plasticity, and plane-stress fracture toughness of 05Cr19Ni55 alloys at pressure up to 30 MPa was investigated. It was established that the crack resistance parameters Kc of alloys decrease with displacement rates decreasing similar to elongation (δ) and reduction of area (ψ) of smooth specimens. The maximum hydrogen influence is achieved at strain rate speeds less than 0.1 mm/min and hydrogen pressures above 15 MPa when δ and Kc of prehydrogenated samples are reduced by 3 times. The plane-strain conditions required for the evaluation of KІc were fulfilled on compact tension 05Cr19Ni55 alloy specimens with thickness above 20 mm under hydrogen pressure 30 MPa and preliminary dissolved hydrogen concentration above 20 wppm. Regardless of the test conditions, the value of the characteristics of plasticity (δ, ψ) and fracture toughness (Kс) of alloy (TO1) specimens oriented in the transverse direction (orientation TV) is significantly lower than that of specimens oriented in the longitudinal direction (LT). Alloy cleaning by vacuum arc remelting and optimization of heat treatment regime increase their hydrogen resistance.