AISI H13 Tool Steel Research Articles

Assessment of laser power and scan speed influence on microstructural features and consolidation of AISI H13 tool steel processed by additive manufacturing

Additive manufacturing can produce parts with complex geometries in fewer steps than conventional processing, which leads to cost reduction and a higher quality of goods. One potential application is the production of molds and dies with conformal cooling for injection molding, die casting, and forging. AISI H13 tool steel is typically used in these applications because of its high hardness at elevated temperatures, high wear resistance, and good toughness. However, available data on the processing of H13 steel by additive manufacturing are still scarce. Thus, this study focused on the processability of H13 tool steel by powder bed fusion and its microstructural characterization. Laser power (97−216 W) and scan speed (300−700 mm/s) were varied, and the consolidation of parts, common defects, solidification structure, microstructure, and hardness were evaluated. Over the range of processing parameters, microstructural features were mostly identical, consisting of a predominantly cellular solidification structure of martensite and 19.8 %–25.9 % of retained austenite. Cellular/dendritic solidification structure displayed C, Cr, and V segregation toward cell walls. The thermal cycle resulted in alternating layers of heat-affected zones, which varied somewhat in hardness and microstructure. Retained austenite was correlated to the solidification structure and displayed a preferential orientation with {001}//build direction. Density and porosity maps were obtained by helium gas pycnometry and light optical microscopy, respectively, and, along with linear crack density, were used to determine appropriate processing parameters for H13 tool steel. Thermal diffusivity, thermal conductivity, and thermal capacity were measured to determine dimensionless processing parameters, which were then compared to others reported in the literature.

Exo-Inoculant Modification of Secondary Phase Precipitation in H13 Tool Steel

Secondary phase carbides in term of type and morphology are considered as the most challenge facing the applications of hot work tool steel. AISI H13 tool steel is one of the most applicable hot work tool steel grades. M23C6, M6C and MC are the common secondary carbides that are forming throughout the martensite matrix of H13 tool steel. In this research, nanoinoculant silicon nitride was added to the molten H13 tool steel to act as an inoculant for the secondary carbide categories through ladle treatment process. By using OM and SEM, it was observed that nanoinoculant has the great impact in the nucleation of secondary carbides into fine shape, in particular M23C6type. In addition, mechanical tests proved that the nucleation of secondary carbides promotes the mechanical properties of hot work H13 tool steel to its ultimate. Impact toughness of the inoculated H13 tool steel was observed with higher value than that was done at the ordinary H13 tool steel. At the meantime, wear resistance of inoculated H13 tool steel was multiplied two times higher than as delivered H13 tool steel.

The effect of tool material grain size on the machining process in ball end milling

Cutting tool material has a significant effect on the temperature of the tool during machining that determines the tool life and machining performance. The objective of this study is to analyze the effect of reducing the grain size of tool material on tool life and cutting performance in terms of tool temperature and cutting forces during ball end milling of tool steel AISI H13. Tool material was prepared from three different sizes of tungsten carbide (WC) powder mixed with cobalt binder and sintered to fabricate ball end mills. The thermo-mechanical properties of the tool material were determined to investigate the effect of grain size. Machining tests were conducted to evaluate the performance of the tool in terms of tool temperature, cutting forces, and tool wear. Results showing a decrease in tooltip temperature with the reduction in grain size of the tool are the main and novel findings of this paper. The same trend was followed in the case of cutting forces and wear.

Effect of scan strategy and heat input on the shear strength of laser cladded Stellite 21 layers on AISI H13 tool steel in as-deposited and heat treated conditions

Coating of hard-facing, wear and corrosion resistant materials on working surfaces of engineering parts made of relatively lower grade materials plays an important role in their service life as this is dictated by the coating material rather than the substrate material. However, the quality of coating in terms of pores- and crack- free deposition, low dilution and good bond strength is vital for the working life of coatings. In this work, bond strength of laser cladded Stellite 21 layers deposited on AISI H13 tool steel with different scanning strategies and line energy is investigated by subjecting the clad-substrate interface to shear force. As Stellite 21 is deposited to improve surface property of high-temperature dies and also for refurbishing worn out dies, bond strength of cladded specimens subjected to a high thermal cycle was also measured. Three sets of shear test specimens of rectangular clad build-up were made with different deposition strategies. First two sets have same laser line energy, but interfacial layers have overlapped clad tracks deposited in two orthogonal directions to study the effect of track orientation on the bond strength. In the third set line energy was doubled by reducing the scan speed. Bond strength was more for shear force applied along the direction of clad tracks. Higher interfacial bond strength of clad tracks parallel to shear stress direction compared to transverse tracks could be resulting by the similar effect that the orientation of fibers in a composite have on its strength. Deposition with higher line energy also had higher bond strength because of more uniform overlapped clad interface. However, specimens subjected to heating up to 1000 °C followed by furnace cooling had much reduced bond strength due to grain coarsening. Results are supported by the micro-structure, micro-hardness, dilution and elemental analyses of cladding and fractured surfaces.

Multi response optimization of CNC end milling of AISI H11 alloy steel for rough and finish machining using TGRA

The AISI H11 tool steel is an essential material used in fabrication of tools & dies. It is an air hardening, high chromium, supreme carbon steel having high wear and abrasion resistant as the main features. Machining is a basic activity in production of tools & dies where the surface finish and metal removal rate play a very essential role. The purpose of the current study is to evaluate the influence of the machining parameters during milling upon the surface roughness (SR) and material removal rate (MRR) of AISI H11 steel. The machining tests have been performed on CNC vertical milling machine. Taguchi grey relational analysis (TGRA) with standard L27 orthogonal array (OA) has been selected to investigate the relationship between surface roughness (SR) and material removal rate (MRR). Optimization was performed considering each input parameter inside the range to obtain best combination of better SR and MRR. Analysis of data has been carried out in MS EXCEL software, and the model significance tests have been conducted using ANOVA method. The 20% weightage for response surface roughness and 80% for material removal rate is assumed for considering the rough machining conditions. The percentage contribution of cutting speed, feed rate and depth of cut for rough machining are 18.48%, 37.49% and 35.61% respectively. Whereas, 80% weightage for response surface roughness and 20% for material removal rate is assumed for considering the finish machining conditions. The percentage contribution of cutting speed, feed rate and depth of cut for finish machining are 71.55%, 13.88% and 1.09% respectively.

Comparative study and modelling of machinability characteristics of single and double tempered AISI H13 steel during hard part finish turning using brazed tungsten carbide tip

The machinability of a material is highly influenced by the surface quality and material removal rate during the machining process. In any machining process, it is cardinal to have a thorough study about how the process parameters affect the machining quality. AISI H13 tool steel is a widely used as a die material at elevated temperatures in industries. A better surface quality of this dies will definitely be efficacious in ensuring product quality and smooth production lines. Thus, this study focuses on the comparative study of the effects of cutting speed, feed rate and depth of cut on surface roughness and material removal rate (MRR) on the hard part finish turning of single tempered and double tempered AISI H13 steel. Initially, annealed workpiece was hardened and tempered at a specified temperature. The machining was done using brazed uncoated tungsten carbide tip as the cutting tool material. Taguchi’s L-25 orthogonal array was implemented for conducting the experiment with the aim of achieving minimal surface roughness (Ra) and maximize the material removal rate (MRR) by determining the optimal combination of input parameter for the desired response. To study the significant effect of the process parameters and the individual percentages contribution on the response parameters, analysis of variance (ANOVA) was performed. Thus, the effect of two type of heat treatment on the machinability characteristics of the material was studied. Also, artificial neural network (ANN) models were developed for all the response parameters i.e. surface roughness and MRR which depicted propitious predicting potential for determining the required responses at any combination of cutting speed, feed rate and depth of cut.

A study and modeling of cutting forces in dry turning of heat treated AISI H13 tool steel with brazed tungsten carbide tip

The machining efficiency and tool life is greatly influenced by the cutting forces generated. As a machining operation is a complex process, it is important to have a thorough idea about the parameters affecting the machining quality. The fine machining quality of the dies produced will be efficacious in the production lines and will also ensure the quality of the product being produced. One such material widely used as hot working dies and casting dies is AISI H13 steel. Thus, this study focuses on investigation of the effects of cutting speed, feed rate and depth of cut on the cutting force components produced during the hard finish turning of heat treated AISI H13 steel using uncoated brazed tungsten carbide tip as the cutting tool material. Initially, annealed H13 steel was hardened and tempered (54 HRC) at specified temperature. Taguchi’s L-25 orthogonal array comprising of 3 factors and 5 levels of each was employed for minimizing the cutting forces generated during machining, with the help of signal to noise ratio evaluation. Analysis of variance (ANOVA) study showed that the effect of feed rate and depth of cut on the cutting forces generated are statistically significant in comparison to cutting speed. Additionally, artificial neural network (ANN) models were developed which depicted promising predicting capabilities for determining the cutting forces at any cutting conditions

Electrical resistivity measured by millisecond pulse-heating in comparison to thermal conductivity of the hot work tool steel AISI H11 (1.2343) at elevated temperature

Selected thermophysical properties of the hot work tool steel AISI H11 (1.2343) were measured in the temperature range from room temperature to the melting temperature. Thermal diffusivity was measured by the laser-flash method; heat capacity by differential scanning calorimetry; linear thermal expansion by push-rod dilatometry; and density at room temperature by an Archimedean balance. From these experimentally obtained data, thermal conductivity was calculated. Additionally, electrical resistivity of AISI H11 (1.2343) was measured by millisecond pulse-heating in the above mentioned temperature range. The measurement results of electrical resistivity as a function of specific enthalpy was combined with results of specific heat capacity measurements by differential-scanning calorimetry to obtain the relation between resistivity and temperature. Based on measured electrical resistivity and thermal conductivity, a Smith-Palmer-plot for the hot work tool steel AISI H11 (1.2343) is obtained for the ferritic and austenitic phases. No linear behaviour – as expected by the Wiedemann-Franz law – is observed in the ferritic phase region. In the high temperature austenitic region, the thermal conductivity can be computed from electrical resistivity using empirical constants of similar austenitic steels or superalloys.

On the wear and corrosion of plasma nitrided AISI H13

Tool steels are applied in a variety of industrial operations providing a good balance of properties. Surface engineering has the potential to improve productivity and further extend the lifetime of metallic components. In the present work plasma nitriding is applied to the hot work AISI H13 tool steel to improve wear and corrosion characteristics. The steel was nitrided in the tempered condition at three different temperatures and pressures for 5 h of duration. At 450 °C of nitriding temperature mainly a diffusion zone is observed while a compound layer is produced at 550 and 650 °C. Both surface and bulk hardness decrease as nitriding temperature is increased. X-ray diffraction indicates that a mixture of both ε and γ′ iron nitrides is produced in all cases. The content of ε-nitride appears to decrease with temperature while γ′-nitride and CrN increase. Working pressure does not lead to significant alterations in phase proportion, hardness and wear resistance after plasma nitriding at a given temperature. However, increasing processing temperature, from 450 to 650 °C, reduces the wear coefficient from 1.19 · 10−7 to 7.06 · 10−8 mm3/N·m, respectively, while from the base steel such coefficients are in the order of 10−5 mm3/N·m. Regarding the corrosion behavior, plasma nitriding at 450 and 550 °C yields higher corrosion potentials, lower current densities and an extensive passivation range, while the tempered substrate, irrespective the condition, exhibits no passivation. From the wear and corrosion perspective it is concluded that plasma nitriding at 450 or 550 °C leads to better corrosion properties while nitriding at 650 °C yields a better wear performance.

Fracture Toughness of a Hot Work Tool Steel Fabricated by Laser‐Powder Bed Fusion Additive Manufacturing

The fracture toughness of AISI H13 tool steel, additively manufactured by laser powder bed fusion (L‐PBF) technique, is studied. The influence of the building direction on fracture toughness is investigated on small notched bending samples heat treated according to two different thermal cycles, namely, quenching and tempering (QT) and only tempering (T). The notch is electro‐discharge machined parallel (P||), perpendicular (P⊥), and longitudinal (L) to the building direction. Both heat treatments, even if to a different extent, delete the as‐built (AB) microstructure, producing secondary carbides precipitation in the martensitic matrix. The microstructure of the directly tempered parts is finer than the quenched and tempered ones. The fracture toughness increases moving from P⊥ to P||. The T samples show a higher apparent fracture toughness in the P||, despite the higher hardness. Secondary cracks formation allows reducing the main crack opening driving force increasing the fracture toughness in P|| samples. This effect is more pronounced in T samples where the stronger precipitation of carbides at the prior melt boundaries promotes secondary cracks. Moreover, in P|| samples the laser tracks act as barriers to crack propagation and as stress dissipators.

Impact on Machining of AISI H13 Steel Using Coated Carbide Tool under Vegetable Oil Minimum Quantity Lubrication

Abstract In machining, final surface quality and dimensional accuracy are the most specified customer requirements. AISI H13 tool steel is used in many fields such as the automotive, aerospace, and defense fields. It is considered to be a hard-to-machine material because of its immense strength. Conventional machining has several negative effects for the environment and human health. It has failed to produce a superior performance on machining of H13 steel. In this study, an eco-friendly minimum quantity lubrication technique is implemented by using a commercially available vegetable-based cutting fluid. An investigation was done on surface characteristics, chip morphology, and intensity of cutting temperature evolved during the machining of H13 steel. Further, wear on the tool of PVD-titanium-aluminum-nitrogen/titanium-nitrogen–coated carbide inserts used for milling was observed for the given input cutting speeds of 30, 45, 60, and 75 m/min and feed rates of 0.08, 1, and 1.2 mm/rev for the constant depth of cut of 1 mm. The results obtained from vegetable oil–based minimum quantity lubrication showed a reduction in the cutting temperature by 52–57 % and 38–45 % and the average surface roughness in the range of 53–64 % and 22–40 % compared to dry and wet machining.

Influence of the etching processes on the adhesion of TiAlN coatings deposited by DCMS, HiPIMS and hybrid techniques on heat treated AISI H11

Ensuring a good adhesion of the coatings to the substrate is one of the key points during the manufacturing of machining and forming tools. The nature of the substrate material and the way it is pre-treated and cleaned before the deposition plays an important role in the adhesion of the coatings. The in-situ cleaning processes as plasma etching and metal ion etching have demonstrated to have an influence on the adhesion of different coating/substrate systems. The introduction of HiPIMS technologies for the in-situ cleaning and the deposition of PVD coatings throughout this technique has opened varied opportunities to improve the performance of the coated parts. Systematic and comparative analysis of the influence of plasma etching itself (PE), plasma etching and metal ion etching (PE + MIE), and plasma etching and HiPIMS etching (PE + HiPE) etching processes on the adhesion of the TiAlN to the hot work tool steel AISI H11 has been performed. Additionally, subsequent to the etching processes, TiAlN coatings have been deposited using DCMS, HiPIMS and hybrid (DCMS/HiPIMS) technologies. Residual stresses of the heat treated AISI H11 were evaluated before and after the different etching process as well as after coating's deposition. It has been shown that the etching process affects the growth direction and microstructure of the TiAlN coatings, especially of those deposited by DCMS and hybrid. For instance, DCMS and hybrid TiAlN coatings deposited after PE have the presence of the TiAlN (200) reflection, not evidenced on the coatings deposited after PE + MIE and PE + HiPE. Moreover, hybrid coatings on PE + HiPE have a preferential (220) growth orientation and a (111) orientation when deposited on PE and PE + MIE cleaned substrate. Finally, in order to evaluate the adhesion of the coatings to the substrate, both scratch test and Rockwell C indentation test were used. The coatings deposited on the mere plasma etched (PE) substrate turn out to be the coatings with the highest critical load Lc3 and the lowest HF standards (HF1–HF3). This behaviour is attributed to the conservation of the substrate's surface integrity and the no promotion of surface tensions that can act in detriment of the adhesion of the coating.

Properties and Corrosion Resistance of Borided AISI H11 Tool Steel

Abstract In this study, the effect of different boriding parameters on some mechanical properties and corrosion resistance of AISI H11 steel, which is extensively used in hot and cold processing applications, was investigated. The grown boride layers were compact and crack-free for all boriding conditions, and they were detected as single phase (Fe2B) at 800 °C and dual phase (FeB + Fe2B) at 900 and 1000 °C. Depending on the treatment condition, the thickness, surface hardness, and Ra values of the coatings were ranged 10.25–94.5 µm, 1704–2015 HV, and 0.285–0.650 µm, respectively. The corrosion resistance was observed to be related to the phase structure, coating thickness, surface roughness, and the density of the boride layers. There is found to be an increase in the corrosion resistance up to almost 65 times after the boriding process, due to the barrier effect of the grown boride layers (such as B2O3).

Development and construction of AISI H11/ZrO2 joints for injection molding tools

Increasing demands in industrial applications and simultaneous efforts to provide long-lasting and cost-efficient tools in the injection molding industry lead to the use of metal–ceramic joints with the aim to combine the specific properties of both materials. Due to its high CTE, zirconium oxide (ZrO2) is used for the ceramic part and is joined with the tool steel AISI H11 (1.2343). In this work, suitable joining techniques with a low heat input and therefore a low thermal load are applied and characterized for the production of metal–ceramic composites. The selection of joining techniques is based on the boundary conditions during the injection molding process, in which the composites have to resist the temperature, pressure, as well as shear and tensile loads. Therefore, besides brazing, other joining processes such as gluing, screwing, shrinking, and clamping were analyzed as possible low temperature joining techniques for ceramic-metal-compounds. The best results for the tensile strengths with 90 MPa were achieved by a brazing process, carried out in vacuum with approximately 10−5 mbar, at a temperature of 920 °C for 5 min, using the commercially available brazing filler alloy CB4.

Effect of tungsten carbide partial dissolution on the microstructure evolution of a laser clad surface

Laser surface modification has been a way to promote wear resistance in dies and molds application. Previously, researchers have succeeded in enhancing surface properties through laser surface modification. The addition of particles in laser cladding process enhanced the surface properties by strengthening the modified AISI H13 tool steel structure. Controlled parameter was laser power, pulse repetition frequency (PRF) and scanning speed with a range of 1.7–2.5 kW, 30–70 Hz and 10.5–24.5 mm s−1 respectively. The powder addition executed by a preplaced method. The grain size and hardness properties of treated samples were characterized using scanning electron microscope (SEM) and hardness Vickers indenter respectively. Surface roughness was characterized using roughness tester. From the findings, tungsten carbide (WC) particles were dissolved homogenously within refined substrate grain structure at higher laser energy. Higher laser scanning speed contributed in uniform particles distribution. The grain refinement with W element in modified layer resulted in maximum hardness of 660 HV. Rapid solidification during laser processing produced metastable phase formation grain refinement, and a higher fraction of grain boundary which resulted in grain boundary strengthening, grain refinement and metastable phase formation. In this paper laser cladding of AISI H13 tool steel with micron size WC particles addition for enhanced surface properties was investigated. These findings are important to design high precision modification of die surface for high temperature forming process.

Tribomechanical Behaviour of TiAlN and CrAlN Coatings Deposited onto AISI H11 with Different Pre-Treatments

In the metalworking industry, different processes and applications require the utilisation of custom designed tools. The selection of the appropriated substrate material and its pre-treatment as well as the protective coating are of great importance in the performance and life time of forming tools, dies, punches and coated parts in general. TiAlN and CrAlN coatings have been deposited onto the hot work tool steel AISI H11 by means of Direct Current Magnetron Sputtering. Prior to the deposition, the steel substrate was modified by the implementation of three different pre-treatments: nitriding of the annealed substrate [Nitr.], heat treatment of the steel (quenching and double tempering) [HT] and nitridation subsequent to a heat treatment of the substrate [HT + Nitr.]. The purpose of this research is to obtain valuable information on the microstructural properties and tribomechanical behaviour of two of the most promising ternary transition metal nitride coatings, TiAlN and CrAlN, when deposited on the AISI H11 steel with different initial properties. The different pre-treatments performed to the steel prior to the deposition favour the tailoring during the design and construction of tools for specific applications. The microstructure, the adhesion and the wear resistance of TiAlN coatings were highly influenced by the substrate preparation. Contrarily, CrAlN results were more independent of the substrate preparation and no high influences were found. For instance, the adhesion of the TiAlN coating varied from 17 to 43 N for the coating deposited onto the HT + Nitr. substrate and the HT substrate respectively, while the lowest and highest adhesion of the CrAlN coating varied between 42 and 53 N for the HT and the HT + Nitr. respectively. Likewise, the wear coefficient of the CrAlN were ten times smaller than those found for the TiAlN coatings, presumably due to the presence of hex-AlN phases and the small differences on the Young´s Modulus of the substrate and the CrAlN coatings.

Process-Structure-Property Relationships of AISI H13 Tool Steel Processed with Selective Laser Melting.

Due to a good combination of high hardness, wear resistance, toughness, resistance to high operating temperatures, and fairly low material cost, AISI H13 tool steel is commonly used in the manufacture of injection molds. Additive manufacturing (AM) such as selective laser melting (SLM), due to the layer-wise nature of the process, offers substantial geometric design freedom in comparison with conventional subtractive manufacturing methods, thereby enabling a construction of complex near-net shape parts with internal cavities like conformal cooling channels. The quality of SLM-manufactured parts mainly depends on the part geometry, build orientation and scanning strategy, and processing parameters. In this study, samples of H13 tool steel with a size of 10 × 10 × 15 mm3 were SLM-manufactured using a laser power of 100, 200, and 300 W; scanning speed of 200, 400, 600, 800, 1000, and 1200 mm/s; and hatch spacing of 80 and 120 µm. A constant layer thickness of 40 µm, 67° scanning rotation between subsequent layers, and a stripe scanning strategy were maintained during the process. The samples were built considering a preheating of 200 °C. The relative density, surface roughness, crack formation, microstructure, and hardness were evaluated. The relative density is shown to increase with increasing the volumetric energy density up to a value of about 60 J/mm3 and then no significant increase can be pointed out; the maximum relative density of 99.7% was obtained. A preheating of 200 °C generally aids to increase the relative density and eliminate the crack formation. The microstructure of built samples shows fine equiaxed cellular-dendritic structure with martensite and some retained austenite. The microhardness of the as-built samples was found to vary from 650 to 689 HV 0.2, which is comparable to a conventionally produced H13 tool steel.

The effect of plasma nitriding treatment time on the tribological properties of the AISI H13 tool steel

In a conventional plasma nitriding mechanism and actual processing, the sample is primarily treated with nitrogen ions. Hence, nitriding is not mainly performed using neutral nitrogen species, such as nitrogen atoms. In this study, a novel method to control nitrogen ions was implemented, and nitriding of the AISI H13 tool steel was performed in electron-beam-excited plasma using neutral nitrogen species and nitrogen ions. The effect of various treatment times on the formation of a hard but brittle compound layer were investigated, along with subsequent tribological change to the surface of the material. The results show that tool steel nitrided by neutral nitrogen species for 6 h produced a diffusion-based nitrided layer (up to 60 μm) without altering the pretreatment surface finish (Ra = 14 nm), and there was a specific wear rate of less than one hundredth (4.3 × 10−7 mm3/N·m) compared with the untreated sample (2.9 × 10−5 mm3/N·m). Conversely, nitriding by ions produced a rough, brittle compound layer on the surface of the tool steel. The samples with a compound layer exhibited a lower coefficient of friction than those with no compound layer.

Preliminary Study of Ultrasound-Assisted Laser Hardening of AISI H13 Tool Steel

This paper presents the viability of ultrasound in assisting the performance of laser hardening process. A nanosecond pulse laser was employed as a heat source in this study to heat and introduce hardened phase in AISI H13 tool steel. The influences of laser power and traverse speed on surface roughness and case depth of laser-irradiated region were experimentally investigated. The laser processing with the assist of ultrasound can improve the surface roughness of laser-hardened area by 7.5% and also increase the case depth by 7.65% compared to the non-ultrasound condition. Under a suitable processing condition, the laser can harden and polish the metal surface at the same when the ultrasound was incorporated in the process. The implication of this study will broaden the viability of ultrasound in the laser surface hardening/polishing of metals.

Recast layer mechanical properties of tool steel after electrical discharge machining with silicon powder in the dielectric

This work investigates the surface modification of quenched and tempered AISI H13 tool steel, widely used in mold-making industry, by sinking EDM with very fine Si powder suspended in the dielectric. The output variable resultant friction coefficients, wear resistance, and hardness of recast layer were measured for different input variables. The 1 A/2.8 μs and 2 A/3.2 μs and 2 A/6.4 μs combinations of discharge current and discharge duration, respectively, produced high hardness, low friction coefficient, and high wear-resistant recast layers, after the formation of martensitic phases in the recast layer as well as C0.17, Fe0.81, Si0.02 carbide. Layer thickness tends to grow with machining time. PMEDM process produced variable amounts of Si in the resultant recast layers, forming iron-silicon carbide phases. Lower wear rates were measured for the high-quality recast layers tested favoring the lifetime of this tool steel in abrasive applications. Martensitic phase formation in the recast layers helps explaining the increased hardness.