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1

Microstructure and properties of the hot work tool steel gradient surface layer obtained using laser alloying with tungsten carbide ceramic powder

Jonda E., Labisz K., Dobrzański L. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 73, nr 2

214--221

EN

Purpose: The aim of the paper is to present the innovatory investigation results of the impact of laser treatment consisting of multiple remelting and alloying using tungsten carbide ceramic powder on the microstructure and properties of hot work tool steel X40CrMoV5-1 surface layer. Design/methodology/approach: Laser heat treatment allows the production of gradient surface layer with a thickness reaching from of tenths of a millimetre even to few millimetres with specific functional properties, including high hardness and abrasion resistance, while maintaining the properties of the substrate material. Findings: Preliminary investigations of the effects of laser radiation on steel surface have showed, that in the surface layer there occur changes concerning the microstructure as well as in the chemical composition different from those occurring during conventional heat treatment. Research limitations/implications: There was determined the effect of laser power on the remelting depth, the depth of the heat affected zone and the width of the laser tray face. There was also measured and compared to the hardness and roughness of the steel processed by remelting with different process parameters. Practical implications: The current application areas for hot work tool steels are constantly growing, and the intensive development of techniques requires the use of new technologies, what leads to production of specific surface layer on materials, in order to meet the extremely difficult working conditions of modern tools. Originality/value: The effect of a HPDL laser melting on the hot work tool steel, especially on their structure and hardness has been studied.

2

Badania odporności na ścieranie warstw napawanych i stali narzędziowych na matryce kuźnicze

Turek J., Okoński S., Piekoszewski W.

Obróbka Plastyczna Metali

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2012

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T. 23, nr 1

39-44

PL

W artykule przedstawiono wyniki badań odporności na zuSycie ścierne stali narzędziowych do pracy na gorąco X37CrMoV5-1 i 55NiCrMoV7 i warstw napawanych materiałami UTOP-38, F-812 i F-818. Badania wykonano na urządzeniu T11 produkcji ITE Radom w temperaturze 250 oC. Najlepsze wyniki uzyskano dla stali X37CrMoV5-1 i 55NiCrMoV7 oraz dla materiału F-818.

EN

The article features an analysis of the resistance to abrasive wear of X37CrMoV5-1 and 55NiCrMoV7 hot-work tool steels and of padding welds overlaid with UTOP-38, F-812 and F-818 materials. The analysis was conducted at the temperature of 250 oC on the T11 testing machine produced by ITE Radom. The best outcome was achieved for X37CrMov5-1 and 55NiCrMoV7 steels and for F-818

3

Modelling of microstructure evolution in hot work tool steels during service

Krumphals F., Wlanis T., Sommitsch Ch., Holzer I., Sonderegger B., Wieser V.

Computer Methods in Materials Science

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2009

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Vol. 9, No. 2

228-233

EN

Hot work tool steels are commonly in use as tools for manufacturing processes of metallic materials at elevated temperatures. To establish a reliable lifetime prediction of the tool, it is necessary to characterize the initial microstructure as well as its evolution during service since the material properties depend on the microstructural configuration. The investigated X38CrMoV5-1 hot work tool steel, which has a body centered cubic lattice structure, forms a distinct dislocation cell and subgrain structure, respectively. In this work a dislocation model for thermal creep using the rate theory with particular consideration of the subgrain boundary behaviour is applied [1]. The subgrains limit the dislocation movement and their diameter is a key parameter in determining the creep rate under many conditions. Prior computations using a dislocation dynamics technique show that the emergence of an organized subgrain structure results as a consequence of elastic energy minimization. The choice of a dislocation model has many advantages over phenomenological models and equations of state with variables not identified with microstructural features in hot work tool steels. For a detailed description of the dislocation density evolution under thermal and cyclic mechanical loads, the dislocation model is adapted to consider both creep and concurrent appearing of low cycle fatigue. Several impacts of different load cases on the microstructure evolution are demonstrated. Simultaneously, the influence of precipitation size evolution and distribution on dislocation movement is considered. The model is compared with experimental investigations of inelastic strains in tools used for hot extrusion applications, i.e. for both container [2] and die [3]. [1] N.M. Ghoniem et al.: "A dislocation model for creep in engineering materials", Res Mechanica 29, 197-219, 1990 [2] C. Sommitsch et al.: "Modelling of creep-fatigue in containers during aluminium and copper extrusion", Computational Materials Science 39, 55-64, 2007 [3] W. Mitter et al.: "Lifetime prediction of hot work tool steels", Lab. Report, Journal of Heat Treatment and Materials Science (HTM), 52, 1997

PL

Tematem pracy jest przewidywanie czasu pracy narzędzi w warunkach eksploatacyjnych. Końcowe własności wyrobu zależą od jego początkowej mikrostruktury oraz zmian tej mikrostruktury podczas wytwarzania. Dlatego za główny cel pracy postawiono sobie modelowanie rozwoju mikrostruktury podczas procesu obróbki cieplnej oraz pracy narzędzi w warunkach eksploatacyjnych. Modelowanie ewolucji mikrostruktury ze szczególnym uwzględnieniem kinetyki wydzieleń wykonano z wykorzystaniem pakietu MatCalc. W pracy analizie poddano stal narzędziową X38CrMoV5-1 o strukturze bcc, która tworzy wyraźną strukturę dyslokacyjną oraz podziarnową. Wykonane obliczenia numeryczne poddano również weryfikacji doświadczalnej.

4

Comparison of the secondary hardness effect after tempering of the hot-work tool steels

Mazurkiewicz J., Dobrzański L. A., Hajduczek E.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 2

119-122

EN

Purpose: of this paper was to examine of the secondary hardness effect after tempering of the developed complex hot-work tool steel 47CrMoWVTiCeZr16-26-8 in relation to standard hot-work tool steel X40CrMoV5-1. Design/methodology/approach: The investigations steels were made using the specimens made from the experimental steel, for which the working 47CrMoW-V-TiCe-Zr16-26-8 denotation was adopted, similar to the ones used in the ISO Standard on using the standard alloy hot-work tool steel X40CrMoV5-1. Both investigated steels were melted in a vacuum electric furnace. Specimens made from the investigated steels were heat treated with austenitizing in salt bath furnaces for 30 minutes in the temperature range of 970-1180 degrees centigrade with gradation of 30 degrees centigrade. Next, the specimens were tempered twice in the temperature range of 450-660 degrees centigrade for 2 hours. Findings: The secondary hardness effect after tempering from temperature of 540 degrees centigrade in the 47CrMoW-V-Ti-CeZr16-26-8 steel and from temperature of 510 degrees centigrade for the X40CrMoV5-1 steel, which is caused by the carbides M4C3 and M7C3 in the 47CrMoWVTiCeZr16-26-8 steel and M7C3 in the X40CrMoV5-1 steel. Practical implications: The developed complex hot-work tool steel 47CrMoWVTiCeZr16-26-8 can be used to the hot work small-size tools which requires higher strength properties at elevated temperature. Originality/value: The obtained results show the influence of the chemical compositions on the secondary hardness effect after tempering in the hot-work tool steel. The secondary hardness effect after tempering determined structure and mechanical properties in this kinds of steels group.

5

Creep fatigue of multi-part container during hot extrusion of copper - Simulation and experimental comparison

Krumphals F., Wlanis T., Redl C., Sommitsch C.

Computer Methods in Materials Science

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2007

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Vol. 7, No. 1

47-53

EN

Extrusion tools exhibit a complex strain-time pattern under a variety of cyclic loading conditions and thus are prone to failure by creep-fatigue interactions. Elevated temperature failure by creep-fatigue processes is time dependent and often involves deformation path dependent interactions of cracks with grain boundary cavities. The extrusion industry tries to accelerate the process by increasing the billet temperature and/or by accelerating the press speed that raise the loading of the tools. On the other side the tool steel producers develop enhanced more homogeneous and cleaner materials in order to increase tools lifetime. Finite element simulation of the extrusion process to get the temperature and stress evolution in the container, coupled with constitutive equations as well as lifetime consumption models in order to calculate both the inelastic strains and the tools lifetime, help to optimise the extrusion process and to compare the operating times of different hot work tool steels. Viscoplastic constitutive models were developed in the past to take into account the inelastic behaviour of the material during creep-fatigue loads. In the present study the Chaboche model was selected and calibrated to the material response of a hot work tool steel between 470°C and 590°C. To extend the prediction capability of Chaboche’s model for non-isothermal processes a temperature-rate term was added to the isotropic hardening rule. Additionally, a creep-fatigue lifetime rule for complex processes was investigated that is independent of single loading parameters, like stress or strain ranges or corresponding maxima, for the description of an entire cycle. Instead this rule evaluates the total damage in each time increment and accumulates that to the lifetime consumption. The present paper shows the development of temperatures, stresses and lifetime consumption during three copper extrusion cycles in a two-part container. The simulation of the heat treatment and the resulting state of the container used was the basis for the subsequent modelling of the cyclic loads during the press cycles. The numerical FEM extrusion simulation consists of the plastic simulation of the billet extrusion with rigid tools as well as of the subsequent simulation of several cycles of the same process, only considering the elastic container and using the time dependent temperature and pressure boundary conditions at the contact surface billet-liner. The reason for this procedure is the much shorter calculation time for the elastic container model with specified boundary conditions in comparison to the plastic extrusion process, especially for several extrusion cycles. Both a constitutive law and a lifetime consumption rule were coupled to the elastic container model in order to get the local inelastic strain rates and the damage rate, respectively. To verify the calculated temperature and pressure boundary conditions at the contact surface billet-liner, a experimental extruding plant was constructed. To obtain a pressure distribution, three holes at different levels were drilled into the container, with only a thin container wall thickness left. The pressure force is transmitted through a plug gauge with a ceramic temperature isolator to a load cell. The system plug gauge /load cell sustains the container wall against damage. The same drilled holes are also used for temperature measurements, measuring points are positioned near the inner wall of the liner, in the middle of the container and for heat control at the outer container region. For the chosen extrusion examples, the simulations led to maximum lifetime consumption in the region of relatively high both temperature and equivalent stresses. These results seem to be reasonable in comparison to real lifetime of copper extrusion containers.

PL

Artykuł przedstawia rozkład pól temperatur, naprężeń oraz zużycia materiału podczas trzech cykli wyciskania miedzi w dwuczęściowym pojemniku. Symulacja procesu obróbki cieplnej oraz ostateczny stan pojemnika zostały wykorzystane jako podstawa do opracowania kolejnych kroków zużycia materiału podczas cyklicznych etapów wyciskania. Symulacja numeryczna MES obejmuje modelowanie plastycznego wsadu i sztywnych narzędzi oraz kilku cykli tego samego procesu dla elastycznego pojemnika przy wykorzystaniu zależnych od czasu warunków brzegowych dla temperatury oraz nacisku. Powodem takiej procedury obliczeniowej jest krótszy czas symulacji niż w przypadku plastycznego procesu wyciskania. W celu weryfikacji obliczonych warunków brzegowych temperatury i nacisku na powierzchni styku, skonstruowano specjalną maszynę laboratoryjną do prowadzenia procesu wyciskania.