AISI H13 Hot Work Tool Research Articles

Failure Analysis of Cryogenically Treated and Gas Nitrided Die Steel in Rotating Bending Fatigue

<div>AISI H13 hot work tool steel is commonly used for applications such as hot forging and hot extrusion in mechanical working operations that face thermal and mechanical stress fluctuations, leading to premature failures. Cryogenic treatment was applied for AISI H13 steel to improve the surface hardness and thereby fatigue resistance. This work involves failure analysis of H13 steel specimens subjected to cryogenic treatment and gas nitriding. The specimens were heated to 1020°C, oil quenched followed by double tempering at 550°C for 2 h, and subsequently, deep cryogenically treated at −185°C in the cryochamber. Gas nitriding was carried out for 24 h at 500°C for 200 μm case depth in NH<sub>3</sub> surroundings. The specimens were subjected to rotating bending fatigue at constant amplitude loading at room temperature. Measurement of surface roughness, hardness, and microstructural analysis indicated improved fatigue life for cryogenically treated specimens as compared to gas nitride, which could be attributed to fine carbide precipitation accountable for the delayed crack initiation and propagation.</div>

Experimental and statistical investigation of electro-erosion machining performance of cryogenic treated hardened AISI H13 hot work tool steel

This study investigated the machinability of AISI H13 hot work tool steel with a hardness of 54 HRC, which has been deep cryogenically treated using the electro-erosion machining technique, one of the unconventional manufacturing methods. The machinability parameters used in the study were determined as current (4, 8 and 12 A), pulse time (200, 300 and 400 µs) and three different electrodes (Copper, Graphite and Tuncop). The experimental design was designed according to the Taguchi L27 model, and machinability tests were carried out to examine the results obtained from the experimental study both experimentally and statistically. When the literature was examined, it was seen that cryogenic treatment was generally applied to electrode materials, and only surface roughness and material wear amounts were examined as output parameters. The original value of the study is the interpretation of the results by applying cryogenic treatment to the test material and exploring the surface roughness and material wear amount, as well as the hole diameters and criterion diameters formed on the treated surfaces after the EDM process. As a result of the study, it was observed that the surface roughness value, the hole diameter, the amount of material wear, and the crater diameter increased with the increase in ampere and impact time. The lowest surface roughness value was 2.266 µm in the graphite electrode material at 4 amps and 200 µs impact time and the highest wear amount was realized as 0.555 g in the copper electrode material 12 amps and 400 µs impact time. The smallest hole diameter was 12.254 mm with a tuncop electrode with a pulse duration of 4 amps and 200 µs, and the lowest crater diameter was 127.301 µm with a graphite electrode at a current of 4 amps and a pulse duration of 200 µs. When the signal-to-noise ratios were examined, the optimum machining parameters for surface roughness, hole diameter, material wear amount, and crater diameter were determined as A2B1C1, A1B3C3, A3B1C1, and A3B1C1, respectively. When the ANOVA results are examined, it is determined that the most effective parameter for the surface roughness is of the current value with 86.54%, the most effective parameter for the hole diameter is the electrode material with 85.20%, the most effective parameter for material wear amount is the electrode material with 45.67% and the most effective parameter for the crater diameter is current value with 75.35%.

Investigation of CMT Welding AISI H13 Hot Work Tool Steel on Weld Bead Geometry, Microstructure, and Mechanical Performance

Investigation of CMT Welding AISI H13 Hot Work Tool Steel on Weld Bead Geometry, Microstructure, and Mechanical Performance

Investigation on Microstructure, Hardness and Fracture Energy of AISI H13 Hot Work Tool Steel by Cyclic Heat Treatment

Investigation on Microstructure, Hardness and Fracture Energy of AISI H13 Hot Work Tool Steel by Cyclic Heat Treatment

Information-rich quality controls prediction model based on non-destructive analysis for porosity determination of AISI H13 produced by electron beam melting

The number of materials processed via additive manufacturing (AM) technologies has rapidly increased over the past decade. As of these emerging technologies, electron beam powder bed fusion (EB-PBF) process is becoming an enabling technology to manufacture complex-shaped components made of thermal-cracking sensitive materials, such as AISI H13 hot-work tool steel. In this process, a proper combination of process parameters should be employed to produce dense parts. Therefore, one of the first steps in the EB-PBF part production is to perform the process parameter optimization procedure. However, the conventional procedure that includes the image analysis of the cross-section of several as-built samples is time-consuming and costly. Hence, a new model is introduced in this work to find the best combination of EB-PBF process parameters concisely and cost-effectively. A correlation between the surface topography, the internal porosity, and the process parameters is established. The correlation between the internal porosity and the melting process parameters has been described by a high robust model (R2adj = 0.91) as well as the correlation of topography parameters and melting process parameters (R2adj = 0.77–0.96). Finally, a robust and information-rich prediction model for evaluating the internal porosity is proposed (R2adj = 0.95) based on in situ surface topography characterization and process parameters. The information-rich prediction model allows obtaining more robust and representative model, yielding an improvement of about 4% with respect to the process parameter-based model. The model is experimentally validated showing adequate performances, with a RMSE of 2% on the predicted porosity. This result can support process and quality control designers in optimizing resource usage towards zero-defect manufacturing by reducing scraps and waste from destructive quality controls and reworks.

Applying Thermo-Reactive Diffusion Method to Surface Coating of H13 Tool Steel Using Ferrovanadium, Ferrochromium, and Misch Metal

The thermo-reactive diffusion (TRD) process is a method for surface hardening that improves the hardness, corrosion resistance, and wear resistance of the materials. In this study, the effect of composition was investigated, by using 8, 12, 16, 20, and 24 wt% of ferrochrome and ferrovanadium with equal amounts, along with 3 wt% aluminum and borax. The TRD process was carried out at 1000°C for 7 hours on AISI H13 hot work tool steel so that a complex coating of chromium-vanadium carbide was formed on the H13 substrate. Optical and scanning electron microscopes were used to evaluate the thickness and microstructure of the samples, respectively. Moreover, the amount of alloying elements and constituent phases on the surface were analyzed by point analysis and X-ray diffraction. The micro-hardness method was used to evaluate the hardness of the samples. The results of this study showed that by increasing the amount of ferroalloy, the hardness and thickness of the coating increase. The optimal composition with 8% ferrochrome and 8% ferrovanadium was found to yield a coating with a thickness of 7.65 μm and a hardness of 2115 HV.

Analysis of wear of a nitrided AISI H13 hot work tool steel in an aluminium hot extrusion process

The present work present experimental results of hot wear testing of AISI H13 tool steel with the aim of replicating the wear mechanisms occurring during hot extrusion process. The hot wear tests were carried out at a temperature of 550 °C and a sliding speed of 0.5 m/s for sliding distances of 1800, 3600 and 5400 m. A pin-on-disk test fixture was designed and fabricated to investigate the sliding between nitrided AISI H13 steel pins and 6063 aluminium alloy disks in a "flat surface-flat surface" conformal contact mode. The different characterisation techniques used (SEM/EDS, XRD) helped to better explain the complex wear mechanisms leading to surface degradation in the tribological couple. Graphitisation phenomenon caused by the dissolution of metastable iron carbide Fe3C was observed to occur after a sliding distance of 3600 m. In addition, coarsening, coalescence and tearing of carbides in the ultimate lower valleys of the degraded surface were observed to occur after 5400 m sliding distance. Nano-indentation technique was used to evaluate the cross-sectional hardness evolution of the nitrided layer, and results showed that the maximum value of hardness of 12.01 ± 0.63 GPa was obtained at the nearest point of the surface. Volume and surface parameters were used to characterise the surfaces before and after wear damage as function of sliding distance. The progressive variation and evolution of the peak material volume parameter (Vmp), core material volume (Vmc), core void volume (Vvc) and dale void volume (Vvv) parameters reached higher values after wear testing at 3600 m sliding distance indicating a synergy between different and complex wear mechanisms.

Combined effects of cryogenic treatment and tempering on microstructural and tribological features of AISI H13 steel

AISI H13 hot work tool steels were subjected to shallow and deep cryogenic treatment. One set of the samples was single tempered, while the other set was double tempered. Cooling specimens to −196 °C increased martensite content and hardness. After tempering, martensite morphology changed, carbides of Cr7C3 and V2C precipitated, and some retained austenite transformed again. Hardness decrease remained limited due to carbide formation. Both cryogenic treatments and tempering processes improved the wear resistance, although the effect of double tempering seemed nebulous. Worn surface analysis revealed that delamination and abrasion predominantly occurred during sliding based on microstructural alteration.

Experimental, Numerical and Statistical Investigation of Cutting Force in the Machining of AISI H13 Hot Work Tool Steel

Bu çalışmada, seramik kesici takımlar ile AISI H13 sıcak iş takım çeliğinin tornalanmasında kesme parametrelerinin kesme kuvveti üzerindeki etkileri araştırılmıştır. Tornalama deneyleri, üç farklı kesme hızında (120, 180 ve 240 m dak-1), üç farklı ilerleme miktarında (0.12, 0.15 ve 0.18 mm dev-1) ve üç farklı talaş derinliğinde (0.6, 1 ve 1.4 mm) kuru kesme şartlarında CNC torna tezgahında gerçekleştirilmiştir. Aynı zamanda, tornalama simülasyonları da sonlu elemanlar analizine (FEA) dayalı olarak Third Wave AdvantEdge yazılımı ile gerçekleştirilmiştir. Deneysel ve nümerik analizler ile elde edilen kesme kuvveti verileri, Taguchi methodu, Anova ve regresyon analizleri kullanılarak istatistiksel olarak analiz edilmiştir. Analiz sonuçları her iki yöntem ile elde edilen esas kesme kuvveti (Fc) değerleri üzerinde sırasıyla %80.97 ve %80.32 katkı oranları ile en etkin parametrenin talaş derinliği olduğunu göstermektedir. Dahası, tornalama simülasyonlarında ve deneysel olarak elde edilen esas kesme kuvveti (Fc) değerleri arasında ortalama %9'lik bir fark elde edilmiştir ve her iki yöntem ile elde edilen Fc değerleri için optimum parametre grubu A3B1C1 (kesme hızı = 240 m dak-1, ilerleme miktarı = 0.12 mm dev-1 ve talaş derinliği = 0.6 mm)’dir.

Experimental Investigation on Nano Oil Added Fluid Influence for the Machining of Hardened AISI H13 Hot Work Tool Steel

Experimental Investigation on Nano Oil Added Fluid Influence for the Machining of Hardened AISI H13 Hot Work Tool Steel

Experimental evaluation and modelling of the boronizing kinetics of AISI H13 hot work tool steel

AbstractIn the study for this contribution, the AISI H13 hot work steel was pack-boronized between 2 and 6 h of exposure time within the temperature range of 800 – 1000 °C. The boriding agent was composed of a powder mixture containing (in weight percent): 90 % of boron carbide (B4C) and 10 % of sodium tetrafluoroborate (NaBF4). The SEM observations showed a less pronounced jagged interface between the boronized layer and the transient zone. A double phase boride layer (FeB and Fe2B) was identified over the surface of AISI H13 steel with the presence of metallic borides inside this compound layer. The mean diffusion coefficient (MDC) method was applied to analyze the growth of iron borides (FeB and Fe2B) as compact layers over the surfaces of AISI H13 steel. The boron activation energies in the two iron borides were also assessed from the present kinetic approach by assuming the Arrhenius relationships. Afterwards, the kinetic model was checked experimentally by considering two extra boriding conditions (925 °C for 1 and 3 h). Finally, the predicted layer thicknesses are in accordance with experimental measurements.

Selective laser melting with changing input energy periodically for production of partially hardened laminate structure in H13 steel

We produced a sub-millimeter-order periodic laminate structure exhibiting different hardness values, phase constituents, and microstructures for an AISI H13 hot work tool steel using a selective laser melting (SLM) process under a combination of different processing conditions applied periodically and continuously (under the concept of “scan strategy”). SLM-scanning with a high energy input beam, which was periodically inserted once every 1.5 mm in the building direction in combination with a low energy input, results in the formation of deep quench-hardened areas and produces a laminate structure possessing different hardness distributions. The surface area (corresponding to the top area) of the SLM product consists of untempered hard martensite because of the rapid cooling of the final heated layer. The local hardened area (corresponding to the intermediate area) and the surrounding area (corresponding to the matrix area) are subjected to tempering due to subsequent reheating to different degrees during the SLM process. Microstructures in all the regions of the top, intermediate, and matrix areas in the laminate structure consist of α'-martensite and austenite (γ) phases. A large amount of retained austenite is also present in the matrix area. The difference in hardness, depending on the area in the laminate structure, is caused by the difference in dislocation densities (related to the degree of tempering depending on the area) and the different amounts of retained austenite. Thus, the results of this study suggest a methodology as well as optimum SLM process conditions (by the “scan strategy”) for producing the laminate structure by controlling the difference in the degree of tempering and altering the Vickers hardness.

Influence of initial defect density on mechanical properties of AISI H13 hot-work tool steel produced by laser powder bed fusion and hot isostatic pressing

ABSTRACT In this study, the microstructure and mechanical properties of martensitic hot-work tool steel AISI H13 produced by laser powder bed fusion (LPBF) under argon atmosphere in different LPBF process times were analysed in the as-built, hardened and tempered (HT) and hot isostatic pressed, hardened and tempered (HIP+HT) condition and compared to conventionally manufactured reference material. Three parameter sets were selected to adjust an initial defect density of 0.6%, 0.9% and 2.2% and thus process time reductions of 17% and 29%. We observed a change in the defect type from almost argon-free microcracks to argon-filled pores with higher scan velocities. Argon embrittlement was evident also in the results of tensile, notched impact toughness and fatigue tests. After HIP+HT a fatigue strength of 972 MPa was obtained for the set with 0.6% microcracks, but only 775 MPa and 718 MPa were obtained for samples with argon porosity.

Experimental investigation of the influence of cutting parameters on surface quality and on the special characteristics of micro-milled surfaces of hardened steels

Micro-milling is one of the most essential technologies to produce micro components, but due to the size effect, it has many special characteristics and challenges. The process can be characterised by strong vibrations, relatively large run-out and tool deformation, which directly affects the quality of the machined surface. This paper deals with a detailed investigation of the influence of cutting parameters on surface roughness and on the special characteristics of micro-milled surfaces. Several systematic series of experiments were carried out and analysed in detail. A five-axis micromachining centre and a two fluted, coated carbide micro-milling tool with a diameter of 500 µm were used for the tests. The experiments were conducted on AISI H13 hot-work tool steel and Böhler M303 martensitic corrosion resistance steel with a hardness of 50 HRC in order to gain relevant information of machining characteristics of potential materials of micro-injection moulding tools. The effect of the cutting parameters on the surface quality and on the ratio of Rz/ Ra was investigated in a comprehensive cutting parameter range. ANOVA was used for the statistical evaluation. A novel method is presented, which allows a detailed analysis of the surface profile and repetitions, and identify the frequencies that create the characteristic profile of the surface. The procedure establishes a connection between the frequencies obtained during the analysis of dynamics (forces, vibrations) of the micro-milling process and the characterising repetitions and frequencies of the surface.

Performance of Multilayer Coated and Cryo-treated Uncoated Tools in Machining of AISI H13 Tool Steel—Part 2: HSS End Mills

This part of the study aimed to investigate the effects of cryogenic treatment applied to uncoated high speed steel (HSS) end mills on cutting forces (Fc), surface roughness (Ra), and tool life. The milling tests were performed at four cutting speeds (40, 50, 60, and 70 m/min), three feeds (0.018, 0.024, and 0.03 mm/rev), and a depth of cut (2 mm) under dry and wet conditions. Three categories of uncoated HSS end mills were used in the tests: conventional heat treated (CHT), cryo-treated (CT), cryo-treated and tempered uncoated (CTT), and TiAlN/TiN multilayer coated (MLC) end mills. The test results showed that the lowest values of Fc and Ra were measured with the use of MLC end mills. However, the cryogenic treatment provided in a reduction in Fc and Ra values. In addition, under wet conditions, the CTT end mills exhibited better performance than the CHT ones by 71.4%. The test results showed while cryogenic treatment is a useful and cheap application in steels, it does not have the ability to compete with coating technology in terms of tool life in milling of hot work tool steel. This paper is organized into two sections. In the first section, cutting performance of cryo-treated and multilayer coated end mills is evaluated. In the second section, performance comparison of cryo-treated WC-Co (Part 1), HSS (Part 2), and MLC end mills in milling of AISI H13 hot work tool steel is presented.

Performance of Multilayer Coated and Cryo-Treated Uncoated Tools in Machining of AISI H13 Tool Steel—Part 1: Tungsten Carbide End Mills

This paper focused on the performance of tungsten carbide end mills in machining of AISI H13 hot work tool steel under dry and wet conditions. The tool performance was evaluated in terms of resultant cutting force (Fc), average surface roughness (Ra) and tool life. In the milling tests, four categories of end mills were used: untreated (U), cryo-treated (CT), cryo-treated and tempered uncoated (CTT) and TiAlN/TiN multilayer coated (MLC). The tests were performed at four cutting speeds (80, 100, 120, 140 m/min), three feeds (0.08, 0.12, 0.16 mm/rev) and a depth of cut (2 mm). The test results showed that the lowest values of Fc and Ra were obtained with the use of MLC end mills. However, the cryogenic treatment was also effective on decreasing Fc and Ra. In addition, while the CTT end mills provided a slight improvement in tool life under dry conditions, they showed a remarkable improvement of 126.1% in comparison with the untreated ones under wet conditions. Although the CTT end mills exhibited a superior performance to U and CT ones, the MLC end mills were much more resistant to abrasive wear. This study is organized into two parts (WC-Co and HSS) to observe the effects of deep cryogenic treatment on performance of two different tool materials and to compare cryo-treated end mills with multilayer coated ones. This part is related to the cryogenic treatment of tungsten carbide end mills, whereas part two is regarding cryo-treated HSS end mills.

Statistical and Experimental Investigation of Hardened AISI H11 Steel in CNC Turning with Alternative Measurement Methods

In recent years, hard turning, an alternative to grinding, which provides low cost and good surface quality, has become an attractive method to the manufacturers. In this experimental study, AISI H11 hot work tool steel that has been hardened up to 50 HRC was subjected to hard turning tests with coated carbide tooling. The analyses were carried out by applying response surface methodology with the analysis of variance method. A total of 27 experiments were modeled utilizing 33 full factorial design and were carried out using a CNC lathe. The effects of the cutting parameters on surface roughness, energy consumption, electric current value, and sound intensity level were investigated. Optimum cutting parameters and levels were determined according to these optimum values. The relationship between cutting parameters and output variables was analyzed with two‐dimensional and three‐dimensional graphics. The results show that while the most effective parameter on the surface roughness was the feed rate (88.62%), the most effective parameter on the sound intensity level was the cutting speed (44.92%). In addition, the cutting depth was the most effective parameter on both electric current (52.20%) and energy consumption (46.15%). Finally, regression coefficients were determined as a mathematical model, and it was observed that this estimated model gave results that were very similar to those achieved with real experiment (correlation values: 97.64% for surface roughness, 98.72% for energy consumption, 97.22% for electric current value, and 91.38% for sound intensity level).

Effect of tempering and cryogenic treatment on wear and mechanical properties of hot work tool steel (H13)

The AISI H13 is a chromium based, medium carbon content hot work tool steel which is widely used in hot working as well as cold working applications. These steels are very popular because of their key characteristics such as high hardness, high strength, high fracture toughness and high wear resistance. These steels are continuously subjected to high mechanical stresses and temperature fluctuations, fatigue and wear loss which results in limited die life. It is therefore necessary to improve the properties of these tool steels. One of the methods to improve the properties of these tool steels is with the help of conventional heat treatment. But no significant improvements in the properties were observed. From the literature survey, it is realized that implementation of cryogenic treatment can improve the properties of tool steel. In the present paper, cryogenic treatment on AISI H13 hot work tool steel is studied with the help of characterization techniques such as hardness, wear and microstructure study. One set of specimens were subjected to conventional heat treatment (HTT) viz. hardening at 1020 °C followed by double tempering at 500 °C. Another set of specimens were subjected to conventional heat treatment followed by deep cryogenic treatment at −196 °C and soft tempering at three different temperatures viz. 200 °C, 300 °C and 400 °C (HTTCT). A modified heat treatment cycle (HTCT) is also proposed with varying soft tempering temperatures viz. 200 °C, 300 °C and 400 °C and comparison is made with HTT and HTTCT. The specimens were tested for hardness, wear and microstructure study. The experimental investigation shows that cryogenically treated specimens shows significant improvement in the hardness and carbide density as compared to conventionally treated specimens. It is thus concluded that HTTCT cycle gives two times higher wear resistance than conventional heat treatment cycle (HTT) because of precipitation of fine tertiary carbides.

Influence of deposition temperature on microstructure formation of Ti-Al-C-N ceramic coatings prepared via pulsed-DC PACVD

Ti-Al-C-N coatings were deposited on AISI H13 hot work tool steel substrates using PACVD method at deposition temperatures of 350, 425 and 500 °C. The results showed that synthesized nanostructured coatings consist of Ti-rich fcc-(Ti,Al)(C,N) and w-AlN nano-grains as well as an amorphous carbon nitride (a-CNx) phase. Increasing of the deposition temperature from 350 °C to 500 °C enhanced the intensity ratio of Disordered peak (ID) to Graphite peak (IG) from 0.94 to 1.13, respectively which is attributed to the increased graphitization of a-CNx phase. Rising the deposition temperature from 350 °C to 425 °C decreased the crystallite size from 11 to 9 nm, while further temperature increase to 500 °C generated larger crystallites of 13 nm. Layers of 2.33, 1.63 and 2.02 μm thickness were developed at different temperatures of 350, 425 and 500 °C, respectively. This behavior caused by increasing the temperature was originated from two competitive factors; the reduction of growth rate induced by more intense ion sputtering and the increase of growth rate induced by grain growth. Another result obtained by increasing the temperature from 350 °C to 500 °C was noticed as a 40% higher surface roughness due to more intense ion sputtering effect and grain growth. Finally, the highest micro-hardness value was measured as 4240 ± 53 HV0.01 for the coating deposited at 425 °C associated with the smallest crystallite size.

Txirbil-harroketan erabilitako ebaketa-jariakinaren eragina laser bidezko prozesu gehigarrian konformaziorako trokelen konponketaren kasuan

Fabrikazio-prozesu gehigarri eta kengarrien arteko konbinaketa oso erabilgarria da geometria konplexuko eta balio-erantsi altuko piezen konponketarako. Prozesuak bateratzeko aukera onena haiek makina bakarrean barneratzea da. Alabaina, bateratze horretan erronka anitz agertzen dira, besteak beste, mekanizazio-prozesuan erabiltzen diren ebaketa-jariakinek jarraiko gehitze-prozesuan izan dezaketen eraginaren ezjakintasunaren ondorioz. Egoera horren aurrean, berotako trokelgintzan ohikoa den AISI H13aren kasurako ebaketa-jariakinarekin kutsaturiko gainazalean laser bidez materiala eranstean ager daitezkeen akatsen azterketa gauzatu da. Olio-maila anitzekin egin dira saiakuntzak, eta gainazal garbian egindako erreferentziazko saiakuntzarekin alderatu dira lorturiko emaitzak. Aldaera morfologikoak nabaritzeaz gain, % 100 olio-kontzentrazioko ebaketa-jariakina erabiltzen den kasuan erantsitako materiala arrakalatu egiten dela ikusi da, eta egoera horretan fabrikaturiko piezak baliogabetu egiten dira. Hortaz, beharrezkoa dela ikusi da AISI H13aren kasuan gehitze-prozesuaren aurretik gainazalean egon daitezkeen ebaketa-jariakinen garbiketa.