AISI H13 Tool Steel Research Articles

Effects of Post-oxidizing Treatment on Melting Loss and Corrosion Resistance of Gas Nitrided AISI H13 Tool Steel

This study conducted gas nitriding on AISI H13 steels, followed by oxidization treatments at various temperatures (560°C, 580°C, 600°C) and soaking times (1 h, 2 h, 3 h), to investigate the melting loss and corrosion resistance of A380 aluminum alloy. The experimental results indicated that the samples of oxynitriding (post-oxidizing treatment after nitrided) at 580°C for 3 h, 600°C for 2 h and 600°C for 3 h have better ability to resist melting loss due to their thicker oxidized layers. The weight loss rate also showed that they are near zero after a 4 h erosion test. The increasing weight loss rate is relative to the appearance of the FexAlySiz compound. In addition, the difference in corrosion current is closely related to the corrosion rate. A smaller corrosion current will lead to a smaller corrosion rate. As a result, increasing the temperature and soaking time of oxidization is advantageous to the corrosion resistance, and a small variation in corrosion current will result in a significant change to the polarization resistance of corrosion. Consequently, the oxide layer can enhance the polarization resistance, and quickly generate a passivation layer that increases the corrosion resistance ability.

Predictive Modeling of Cutting Forces and Tool Wear in Hard Turning using Response Surface Methodology

In the present study, an attempt has been made to investigate the effect of cutting parameters on cutting forces and tool wear in hard turning of AISI H13 tool steel using ceramic tool. The machining experiments were performed in accordance to Central Composite Design (CCD). The second order regression model of machining forces and tool wear has been developed. The influence of each operating factors have been studied through analysis of variance (ANOVA) technique. The obtained results reveal that, cutting speed and depth of cut have significant effect on feed force whereas feed rate and depth of cut are factors that significantly influences on thrust force. The depth of cut and cutting speed has predominant effect on tool wear. Feed rate have less significant effect on tool wear. But, in case of cutting force modeling, all the three parameters have significant effect. Key parameters and their effects on tool wear and cutting forces have also been presented in graphical contours which may help for choosing operating parameter preciously. Optimized model indicates desirability level for economy in hard turning process.

Experimental investigation and 3D finite element prediction of the white layer thickness, heat affected zone, and surface roughness in EDM process

An axisymmetric three-dimensional model for temperature distribution in the electrical discharge machining process has been developed using the finite element method to estimate the surface integrity characteristics of AISI H13 tool steel as workpiece. White layer thickness, depth of heat affected zone, and arithmetical mean roughness consisting of the studied surface integrity features on which the effect of process parameters, including pulse on-time and pulse current were investigated. Additionally, the experiments were carried out under the designed full factorial procedure to validate the numerical results. Both numerical and experimental results show that increasing the pulse on-time leads to a higher white layer thickness, depth of heat affected zone, and the surface roughness. On the other hand, an increase in the pulse current results in a slight decrease of the white layer thickness and depth of heat affected zone, but a coarser surface roughness. Generally, there is a good agreement between the experimental and the numerical results.

Carbon Distribution and the Influence on the Tempering Behaviour in a Hot-Work Tool Steel Aisi H11

The microstructure of the common hot-work tool steel AISI H11 has been characterized by atom probe tomography with the focus on the carbon distribution after the hardening treatment and in the early stages of tempering. The carbon distribution shows significant differences within the probed volumes, regions differently affected by carbon segregation can be observed in some specimens. In all samples pronounced carbon segregation to dislocations and cluster formation is observed. Through all hardened samples no segregation of any substitutional elements has taken place. Heating to 500°C does not significantly change the elemental distribution. Carbon enriched interlath austenite films with peak carbon levels of 6 to 9 at% show a thickness increase with increasing λ. These films and the pre-existing carbon clusters have been found to be nucleation sites for carbide formation during heating to 610°C.

Computational Analysis of Material Flow During Friction Stir Welding of AA5059 Aluminum Alloys

Workpiece material flow and stirring/mixing during the friction stir welding (FSW) process are investigated computationally. Within the numerical model of the FSW process, the FSW tool is treated as a Lagrangian component while the workpiece material is treated as an Eulerian component. The employed coupled Eulerian/Lagrangian computational analysis of the welding process was of a two-way thermo-mechanical character (i.e., frictional-sliding/plastic-work dissipation is taken to act as a heat source in the thermal-energy balance equation) while temperature is allowed to affect mechanical aspects of the model through temperature-dependent material properties. The workpiece material (AA5059, solid-solution strengthened and strain-hardened aluminum alloy) is represented using a modified version of the classical Johnson-Cook model (within which the strain-hardening term is augmented to take into account for the effect of dynamic recrystallization) while the FSW tool material (AISI H13 tool steel) is modeled as an isotropic linear-elastic material. Within the analysis, the effects of some of the FSW key process parameters are investigated (e.g., weld pitch, tool tilt-angle, and the tool pin-size). The results pertaining to the material flow during FSW are compared with their experimental counterparts. It is found that, for the most part, experimentally observed material-flow characteristics are reproduced within the current FSW-process model.

Thermo fatigue cracking of die casting dies

The investigation of aluminium alloy die casting die failures was done with the emphasis on thermal cracks. The aim of the study was to prolog the in-service die life by cladding with maraging steels, which would be economically beneficial. A vast analysis of thermal fatigue cracks in aluminium alloy die casting is done. Immersion test apparatus was developed, which enables simulation of conditions during aluminium alloy die casting and enables controlled thermal fatigue testing of materials. Special specimens made of the AISI H13 tool steel were differently heat treated. On the edges of some specimens, the maraging steel is cladded using gas tungsten arc (GTA) welding. These samples are tested in as-welded and in optimally aged condition. After completion of a particular number of cycles, the specimen edge surfaces were examined visually. The specimens were then sectioned and examined with light and scanning electron microscopy (SEM). The energy-dispersive X-ray spectroscopy (EDS) mapping of areas around the cracks was done. The number and length of thermal fatigue cracks were statistically evaluated and a Vickers hardness profiles were measured. The results confirmed a good thermal fatigue resistance of the properly hardened H13 hot work tool steel. The surface cracks growth is accelerated by surface oxidation.

Constitutive Laws for the Deformation Estimation of Extrusion Die in the Creep-Fatigue Regime

Tools are exposed to severe working conditions during the hot extrusion process. In particular, dies and mandrels can be subjected to an excessive amount of deformation as a result of the developed high cyclic loads and temperatures. In this scenario, a physical experiment reproducing the thermo-mechanical conditions of a mandrel in a porthole die was performed with the Gleeble machine on the AISI H11 tool steel with the aim to investigate the mechanisms that influence the die deformation. The design of experiment consisted of 4 levels of temperature, 3 levels of stress and 3 types of load, i.e. pure creep, pure fatigue and creep-fatigue. In all the testing conditions, a comparable pattern of the mandrel displacement-time curve was found reproducing the 3 stages of softening typical of the strain evolution in a standard creep test but with a marked primary phase. Thus, with the aim to identify an easy-applicable equation to estimate the die deformation, the time hardening creep law was chosen. Coefficients of the time-hardening law were optimized, for each testing condition, on the basis of experimental data starting from values for similar alloys taken from the literature. Results in terms of mandrel displacement were then compared to experimental data for the creep-fatigue condition at different stress and temperature levels. The values found were validated against additional experimental data performed with different specimen geometries. A good average agreement was found between experimental and numerical results. The developed procedure was then applied to an industrial die.

Influence of Input Parameters on the Characteristics of the EDM Process

This paper presents the results of experimental studies carried out to conduct a comprehensive investigation on the influence of Electrical Discharge Machining (EDM) input parameters on characteristics of EDM process. The studied process characteristics included machining features, embracing material removal rate, tool wear ratio, and arithmetical mean roughness, as well surface integrity characteristics comprising of the thickness of white layer and the depth of heat affected zone of AISI H13 tool steel as workpiece. The experiments performed under the designed full factorial procedure, and the considered EDM input parameters included pulse on-time and pulse current. The results of this study could be utilized in the selection of optimum process parameters to achieve the desired EDM efficiency, surface roughness, and surface integrity when machining AISI H13 tool steel.

Experimental investigations on cryogenic cooling by liquid nitrogen in the end milling of hardened steel

Milling of hardened steel generates excessive heat during the chip formation process, which increases the temperature of cutting tool and accelerates tool wear. Application of conventional cutting fluid in milling process may not effectively control the heat generation also it has inherent health and environmental problems. To minimize health hazard and environmental problems caused by using conventional cutting fluid, a cryogenic cooling set up is developed to cool tool–chip interface using liquid nitrogen (LN 2). This paper presents results on the effect of LN 2 as a coolant on machinability of hardened AISI H13 tool steel for varying cutting speed in the range of 75–125 m/min during end milling with PVD TiAlN coated carbide inserts at a constant feed rate. The results show that machining with LN 2 lowers cutting temperature, tool flank wear, surface roughness and cutting forces as compared with dry and wet machining. With LN 2 cooling, it has been found that the cutting temperature was reduced by 57–60% and 37–42%; the tool flank wear was reduced by 29–34% and 10–12%; the surface roughness was decreased by 33–40% and 25–29% compared to dry and wet machining. The cutting forces also decreased moderately compared to dry and wet machining. This can be attributed to the fact that LN 2 machining provides better cooling and lubrication through substantial reduction in the cutting zone temperature.

Development of Surface Roughness Prediction Model for High Speed End Milling of Hardened Tool Steel

The quality of the surface plays a very important role performance of milling as a good-quality milled surface in a variety of manufacturing industries including the aerospace and automotive sectors where good quality surface significantly improves fatigue strength, corrosion resistance, or creep life. This study discussed the issue of surface machined quality and the effort taken to predict surface roughness. For thus purpose , hardened materials AISI H13 tool steel with hardness of 48 Rockwell Hardness (HRC) was chosen for work material. Machining was done at High Cutting speed (Vc) from 150 up to 250 m/min, feedrate (Vf) 0005-0.15 mm/rev and depth of cut (DOC) 0.1-0.5mm. The analysisi and observation of the surface roughness were done by using optical surface roughness machine. Response Surface Methodology (RSM) Model was used to design the prediction model with parameters generated by using Central Composite Face (CCF) methods. A prediction model developed with 90% accuracy with the conclusion of feedrate as the main contributor to surface roughness followed by cutting speed. Therefore, RSM has been proven to be an efficient method to predict the surface finish during end-milling of H13 tool steel using TiAIN coated carbide tool inserts under dry conditions.

Machinability Improvement by Workpiece Preheating during End Milling AISI H13 Hardened Steel

Hardened materials like AISI H13 steel are generally regarded as s difficult to cut materials because of their hardness due to intense of carbon content, which however allows them to be used extensively in the hot working tools, dies and moulds. The challenges in machining steels at their hardened state led the way to many research works in amelioration its machinability. In this paper, preheating technique has been used to improve the machinability of H13 hardened steel for different cutting conditions. An experimental study has been performed to assess the effect of workpiece preheating using induction heating system to enhance the machinability of AISI H13. The preheated machining of AISI H13 for two different cutting conditions with TiAlN coated carbide tool is evaluated by examining tool wear, surface roughness and vibration. The advantages of preheated machining are demonstrated by a much extended tool life and stable cut as lower vibration/chatter amplitudes. The effects of preheating temperature were also investigated on the chip morphology during the end milling of AISI H13 tool steel, which resulted in reduction of chip serration frequency. The preheating temperature was maintained below the phase change temperature of AISI H13. The experimental results show that preheated machining led to appreciable increasing tool life compared to room temperature machining. Abrasive wear, attrition wear and diffusion wear are found to be a very prominent mechanism of tool wear. It has been also observed that preheated machining of the material lead to better surface roughness values as compared to room temperature machining.

Surface Roughness and Wear Behavior of Laser Machined AISI H13 Tool Steel

The effects of laser machining process parameters namely, scan speed and frequency on wear performance of AISI H13 hot work tool steel were investigated in this study. The process parameters are combined with wear process factors and the responses of wear tests were evaluated. The results showed that both friction coefficient and wear rate are affected by process parameters. The average friction coefficient and wear rate increased with an increase in frequency at each set of scan speed. Lowest scan speed and highest frequency produced higher surface roughness and rough texture form.

Surface Integrity of AISI H13 in End Milling and Electrical Discharge Machining Process

Industries are forced to seriously evaluate their design and manufacturing of their products due to the competition in the marketplace. Product characteristics such as tolerance specification, appearance, and service life now become a major concern for machined components. One of the most important aspects in machined components is surface integrity. It involves mainly the surface roughness and micro hardness changes during machining operation, which should be controlled and monitored to fulfill the product functions and customer needs. This paper presents the comparison effect of the end milling and EDM parameters on the surface integrity of AISI H13 tool steel (HRC50 3). The parameters studied were the cutting speed (224 m/min – 280 m/min), feed rate (0.25 mm/tooth) and depth of cut (0.3 mm-0.8 mm for end milling process. Whereas for EDM, the parameters studied were the peak current (1 and 4 A), pulse ON-time (6 and 12 μs), and pulse OFF-time (2 μs). The electrodes used were graphite and copper. In this study, the workpiece surface and recast layer were examined using an optical microscope. The observation revealed that both processes of end milling and EDM had cause the formation of three layers structure, i.e. white, martensite quenched and bulk material layers. The subsurface alteration for EDM process is considered rigorous as compared with the end milling process. Damages beneath the machined surface such as micro cracks and void were observed for EDM process, and microscopic pitting and surface roughning for end milling process. The measurement of the microhardness beneath the machined surface of AISI H13 was carried out using Vickers microhardness tester to characterize its mechanical properties. It was found that the highest hardness of 1010 Hv was in the white layer, and hardness of martensite quench layer was 423 Hv, which was lower than the bulk material layer of 430 Hv in EDM process. Whereas, a maximum of 550 Hv was measured directly underneath the generated surface, i.e. 30% more as compared to the hardness of the basic material in the end milling process.

The Effect of Scan Speed on Engraving Depth and Surface Roughness of AISI H13 Tool Steel

The aim of this study is to investigate the effect of scan speed and frequency on surface roughness and engraving depth of AISI H13 hot work tool steel. The experimental studies were conducted by fiber laser marker machine. The relationship between the parameters is showed that the highest surface roughness and depth values were achieved at lowest scan speed (125mm/s). The depth and surface roughness of engraved geometry was decreased at increase in scan speed. It was concluded that, the surface roughness and depth can be controlled by scan speed and frequency.

Thermal Fatigue Testing of Bulk Functionally Graded Materials

Thermal fatigue resistance is one of the most important characteristics of the materials subjected to rapid temperature changes, i.e., high-pressure die casting, hot forging. Therefore the aim of the present study was to determine the suitability of using the functionally graded materials (FGM) in applications subjected to thermal fatigue. A specially designed thermal fatigue test was utilized, developed to be used on servo-hydraulic testing machine, Gleeble 1500D. The FGM samples were prepared using a laser cladding method that ensures sound welds. Two different filler materials on the AISI H13 tool steel were utilized, varying in the content of the silicon. The gradation in the properties was made by changing silicon content with varying welding parameters, and thus achieving gradation of the secondary carbide content. The test results show that the silicon distribution has large effect on thermal fatigue resistance; the resistance is decreasing with the increasing the content of silicon in the filler material. This was studied through the sequence of crack formation. The results of this study will contribute to prolonged use of die casting tools.

Modificações microestruturais e tribológicas nos aços-ferramenta AISI H13 e DIN X100CrMoV 8-1-1 produzidas por nitretação a plasma

The tool-steels AISI H13 and DIN X100CrMoV 8-1-1, which are used for different applications, were plasma nitrided in a low concentration nitrogen atmosphere at 500°C in order to increase the wear resistance. Then, metallurgical properties of these steels before and after nitriding were evaluated, and wear tests were also performed. The results demonstrated that plasma nitriding successfully increased the wear resistance on both steels. This study also demonstrated how the modified properties contributed in this way. Key words: plasma nitriding, wear, H13, DIN X100CrMoV 8-1-1.

Comparative Study and Mathematical Modeling of Machining Parameters in Ultrasonic-Assisted EDM of AISI H13 Tool Steel by the Application of Workpiece Vibration

The correct selection of the machining parameters is one of the most significant issues to take into consideration in Ultrasonic-assisted Electrical Discharge Machining (US-EDM) and EDM processes. In the present work, a study has been made to develop and extract statistical models to show the relationship between important machining performance data (material removal rate (MRR), tool wear ratio (TWR) and surface roughness Ra) and the input machining parameters (pulse current, and pulse-on time) in the EDM and US-EDM of AISI H13. The models obtained were used to analyze the effects of input parameters on machining performance. In addition, a comparative study was carried out to investigate the effect of ultrasonic vibration of the workpiece on machining performance. The results show that Ultrasonic vibration of the workpiece can significantly reduce the inactive pulses and improves the stability of process. Also US-EDM is effective in attaining a high material removal rate (MRR) in finishing regime in comparison with conventional EDM. The results of Analysis of Variance (ANOVA) indicate that the proposed mathematical models can adequately explain the performance within the limits of the factors being studied.

Finite element and dimensional analysis algorithm for the prediction of mechanical properties of bulk materials and thin films

In this work, the applicability of a new algorithm for the estimation of mechanical properties from instrumented indentation data was studied for thin films. The applicability was analyzed with the aid of both three-dimensional finite element simulations and experimental indentation tests. The numerical approach allowed studying the effect of the substrate on the estimation of mechanical properties of the film, which was conducted based on the ratio h max /l between maximum indentation depth and film thickness. For the experimental analysis, indentation tests were conducted on AISI H13 tool steel specimens, plasma nitrated and coated with TiN thin films. Results have indicated that, for the conditions analyzed in this work, the elastic deformation of the substrate limited the extraction of mechanical properties of the film/substrate system. This limitation occurred even at low h max /l ratios and especially for the estimation of the values of yield strength and strain hardening exponent. At indentation depths lower than 4% of the film thickness, the proposed algorithm estimated the mechanical properties of the film with accuracy. Particularly for hardness, precise values were estimated at h max /l lower than 0.1, i.e. 10% of film thickness.

Microstructural evolution during friction surfacing of tool steel H13

Coatings of AISI H13 tool steel were made on low carbon steel by friction surfacing. Detailed microstructural studies and microhardness tests were carried out on the coatings. Studies revealed defect-free coatings and sound metallurgical bonding between the coating and the substrate. In addition, mechanical interlocking on a very fine scale was observed to occur between the coating and the substrate. Coatings exhibited martensitic microstructure with fine grain size and with no carbide particles. Coatings in as-deposited condition showed very high hardness (58 HRC) compared to the mechtrode material in annealed condition (20 HRC). Based on these findings, microstructural evolution during friction surfacing of H13 tool steel is discussed. The current work shows that friction surfaced tool steel coatings are suitable for use in as-deposited condition. Further improvements in coating microstructure and properties are possible with appropriate post-surfacing heat treatment.

Microstructure and corrosion behaviour of pulsed plasma-nitrided AISI H13 tool steel

The effect of pulsed plasma nitriding temperature and time on the pitting corrosion behaviour of AISI H13 tool steel in 0.9% NaCl solutions was investigated by cyclic polarization. The pitting potential ( E pit) was found to be dependent on the composition, microstructure and morphology of the surface layers, whose properties were determined by X-ray diffraction and scanning electron microscopy techniques. The best corrosion protection was observed for samples nitrided at 480 °C and 520 °C. Under such experimental conditions the E pit-values shifted up to 1.25 V in the positive direction.