An Experimental Study of Temperature Effect on Properties of Nitride Layers on X37CrMoV51 Tool Steel Used in Extrusion Aluminium Industry

This article is devoted to the issues of thermal softening of materials in the surface layer of forging tools. The research covers numerical modeling of the forging process, laboratory tests of tempering of nitrided layers, and the analysis of tempering of the surface layer of tools in the actual forging process. Numerical modeling was supported by measuring the temperature inside the tools with a thermocouple inserted into the tool to measure the temperature as close to the surface as possible. The modeling results confirmed the possibility of tempering the die material. The results of laboratory tests made it possible to determine the influence of temperature on tempering at different surface layer depths. Numerical analysis and measurement of surface layer microhardness of tools revealed the destructive effect of temperature during forging on the tempering of the nitrided layer and on the material layers located deeper below the nitrided layer. The results have shown that in the hot forging processes carried out in accordance with the adopted technology, the surface layer of working tools is overheated locally to a temperature above 600 °C and tempering occurs. Moreover, overheating effects are visible, because the surface layer is tempered to a depth of 0.3 mm. Finally, such tempering processes lead to a decrease in the die hardness, which causes accelerated wear because of the abrasion and plastic deformation. The nitriding does not protect against the tempering phenomenon, but only delays the material softening process, because tempering occurs in the nitrided layer and in the layers deeper under the nitrided layer. Below the nitrided layer, tempering occurs relatively quickly and a soft layer is formed with a hardness below 400 HV.

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“…in its entire volume. The recent research results confirm such a negative effect of annealing of nitride layers on X37CrMoV51 tool steel [23].…”

Section: Test Results For Tempering Of Nitrided Layers Under the Conditions Of The Actual Forging Processsupporting

confidence: 61%

“…In the case of a sample annealed entirely in laboratory conditions, these changes are visible in its entire volume. The recent research results confirm such a negative effect of annealing of nitride layers on X37CrMoV51 tool steel [ 23 ].…”

Section: Resultsmentioning

confidence: 62%

Advanced Complex Analysis of the Thermal Softening of Nitrided Layers in Tools during Hot Die Forging

2021

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“…The microstructural changes observed in this area point to strong degradation of the die material. The literature data show that the decomposition of the nitrided layer is accompanied by denitriding [37]. The authors of the work [38] demonstrate that the denitriding process is accompanied by penetration of nitrogen into the material.…”

Section: Microscopic Observations In Area Imentioning

confidence: 96%

Influence of the nitrided layer thickness of dies made of two types of tool steel used in hot extrusion of valve forgings made of nickel–chromium steel on the durability of these tools

Hawryluk

Lachowicz

Janik

et al. 2021

Archiv.Civ.Mech.Eng

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The study constitutes an analysis of the durability of dies used in the first operation of producing valve forgings from chromium–nickel steel (NCF 3015) for motor trucks. The average durability of the dies (subjected to standard thermal treatment and nitriding) in this operation equals about 800 forgings. To perform an in-depth analysis of the effect of the nitrided layer thickness (0.1 mm and 0.2 mm) and the tool material (W360 and QRO90) on the possibilities of increasing the die durability, complex studies were carried out, which included: a macroscopic analysis combined with 3D scanning, microstructural examinations using a scanning microscope and a metallographic microscope, as well as hardness measurements. A minimum of three tools were tested for different variants, and for each of them, one representative die was selected for detailed examinations. The research showed the presence of abrasive wear, thermo-mechanical fatigue and traces of adhesive wear as well as plastic deformation on the surface of the working impressions. Also observed was the effect of the extruded material sticking to the tools (high friction and the presence of intermetallic phases in the extruded material) and the forging being blocked in the smallest section of the die, which is a critical factor causing a production shutdown and the necessity of tool replacement. The highest mean durability equalling 2600 forgings was obtained for the dies with a lower carbon content and a higher content of vanadium and the nitrided layer thickness at the level of 0.2 mm. The lowest mean durability (after one forging item) was recorded for the dies made of steel with a higher carbon content and a higher chromium content, forming less stable compound carbides and the thickness layer at the level of 0.1 mm.

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“…Whereas for the material characterization of the base material within the scope of this study, a very detailed modeling could be referenced, a single static hardness value in connection with a constant layer thickness was defined as a first approach for the properties of the nitrided protection layer. As the properties of this layer in terms of hardness during the adjustment process are essentially determined by the set temperatures and treatment times [ 17 , 28 ], it can be assumed that the properties of this layer also undergo an evolution during the ongoing process. For this reason, a characterization analogous to the one described by Müller et al [ 19 ] is already in progress in order to implement the results in the next iteration into the model described here.…”

Section: Future Workmentioning

confidence: 99%

“…While the consideration of nitriding layers in wear calculations with the Archard model is highly relevant in general, the use of the surface layer distance to retrieve the corresponding tool hardness during FE-calculations is problematic. Since typical nitriding depths achievable in industrial applications reach values of approximately 0.1 mm to 0.4 mm [ 16 , 17 ], it is necessary to apply an even smaller element size for the discretization of the surface layer. Considering this, Groseclose could successfully use this model in a 2D calculation of an extrusion process featuring relatively simple tool geometries while maintaining the necessary small element size.…”

Section: Introductionmentioning

confidence: 99%

Multi-Layer Wear and Tool Life Calculation for Forging Applications Considering Dynamical Hardness Modeling and Nitrided Layer Degradation

et al. 2020

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As one of the oldest shaping manufacturing processes, forging and especially hot forging is characterized by extreme loads on the tool. The thermal load in particular is able to cause constant changes in the hardness of the surface layer, which in turn has a decisive influence on the numerical estimation of wear. Thus, also during numerical wear, modeling hardness changes need to be taken into account. Within the scope of this paper, a new implementation of a numerical wear model is presented, which, in addition to dynamic hardness models for the base material, can also take into account the properties of a nitride wear protection layer as a function of the wear depth. After a functional representation, the new model is applied to the wear calculation of a multi-stage industrial hot forging process. The applicability of the new implementation is validated by the evaluation of the occurring hardness, wear depths and the locally associated removal of the wear protection layer. Consecutively, a tool life calculation module based on the calculated wear depth is implemented and demonstrated. In general, a good agreement of the results is achieved, making the model suitable for detailed 2D as well as large 3D Finite Element calculations.

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An Experimental Study of Temperature Effect on Properties of Nitride Layers on X37CrMoV51 Tool Steel Used in Extrusion Aluminium Industry

Cited by 11 publications

References 30 publications

Advanced Complex Analysis of the Thermal Softening of Nitrided Layers in Tools during Hot Die Forging

Advanced Complex Analysis of the Thermal Softening of Nitrided Layers in Tools during Hot Die Forging

Influence of the nitrided layer thickness of dies made of two types of tool steel used in hot extrusion of valve forgings made of nickel–chromium steel on the durability of these tools

Multi-Layer Wear and Tool Life Calculation for Forging Applications Considering Dynamical Hardness Modeling and Nitrided Layer Degradation

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