Hot Work Tool Steel

Metin ZEYVELİa, *, Halil DEMİRa ve Hasan Basri ULAŞb, Abdulkadir GÜLLÜb a, * Karabük Üniversitesi, Teknik Eğitim Fakültesi, Makine Eğitimi Bölümü, 78050, Karabük, hdemir@karabuk.edu.tr , mzeyveli@karabuk.edu.tr b Gazi Üniversitesi, Teknik Eğitim ...

X32CrMoV33 hot work tool steel samples coated with AlTiN and AlTiON were submitted to thermal cycling under conditions that approximate thixoforming of steels and to sliding wear tests at 750 ?, measured to be the cavity surface temperature shortly after the steel slurry is forced into the thixoforming die. AlTiN and AlTiON coatings provide adequate protection against oxidation of the tool steel substrate, but fail to avoid thermal fatigue cracking. This is attributed to the extensive softening of the substrate, the thermal expansion mismatch between the hot work tool steel and the coatings and residual compressive stresses inherited from the deposition process. The impact of AlTiN and AlTiON coatings on the high temperature wear resistance, on the other hand, is favourable. The improved wear resistance is attributed to the stable, protective surface oxide films.

Purpose: The aim of the research is the investigation of the structure and mechanical properties of monolayers CrN, TiN and multilayers TiN/TiAlN and Ti/TiAlN coatings deposited by PVD techniques onto the substrate from the X37CrMoV5-1 steel and CuZn40Pb2 brass. Design/methodology/approach: The microhardness tests were made on the dynamic ultra-microhardness tester. Tests of the coatings’ adhesion to the substrate material were made using the scratch test. The wear and friction tests were performed on a standard pin-on-disc device. Findings: The monolayer PVD coatings deposited onto hot work steel and brass substrate demonstrate the high hardness, adhesion and wear resistance. The critical load LC2, which is in the range 32-60 N, depends on the coating and substrate type. The friction coefficient for the investigated coatings is within the range of 0.33-0.75. Practical implications: The investigation results will provide useful information to applying the PVD coating for the improve...

Purpose: The aim of the paper was to compare the structure, mechanical propeties, adhesion and wear resistance of the monolayer TiN PVD coatings deposited onto heat treated and plasma nitrided hot work tool steel X37CrMoV5-1. Design/methodology/approach: The microhardness tests of the PVD coatings were made with use of a dynamic ultra-microhardness tester. The topography of the surface and the structure of the PVD coatings was observed with use of scanning electron microscopy.The evaluation of the adhesion of coatings to the substrate was made with use of the scratch test. The wear and friction tests were performed with use of a pin-on-disc device at the room temperature and at the temperature of 500°C. Findings: IIn case of the TiN coating deposited onto the nitrided hot work steel X37CrMoV5-1 a very good adhesion to the substrate has been revealed in comparison with the TiN coating deposited onto the heat treated hot work steel. Taking into account the results of measurements, one...

In this paper we report the influence of temperature (260 to 510 °C) on the AISI H13 steel microstructure and hardness in pulsed plasma nitriding processes. The experimental results show that bulk nitrogen penetration is well represented by a temperature-activated law. Even at the lowest studied temperatures, grain boundary diffusion causes nitrogen to move relatively deep in the bulk sample. The microstructure was studied by X-ray diffraction analysis at grazing angle and in the Bragg–Brentano configuration. Scanning Electron Microscopy with spatially resolved X-ray energy disperse spectroscopy was also employed to map nitrogen influence on the morphology of the material. Also, surface (frontal) and profiling nano-indentation was utilized to elucidate the effect of the temperature on the nitrited material hardness.

High temperature abrasive wear performance of X32CrMoV33 hot work tool steel with and without an Al0.61Cr0.39N coating was investigated under three body abrasion conditions. The Al0.61Cr0.39N coating has a remarkable impact on the wear resistance of the X32CrMoV33 hot work tool steel. Extensive oxidation co-occurring with abrasive wear at 750 °C leads to substantial material loss in the latter. The poor adherence and limited ductility of Fe3O4 promote the failure of the thick oxide scale on the tool steel sample impairing its resistance to abrasion at elevated temperatures. The material loss of the AlCrN-coated tool steel, however, is nearly two orders of magnitude smaller. This is attributed to the adhesive and highly plastic Cr2O3 film that forms on the coating and sustains the abrasion. The much reduced oxidation in the coated sample suppresses the synergy between oxidation and wear, and improves the resistance to abrasive wear. Much higher hardness of the AlCrN coating with respect to the substrate is also believed to be instrumental.▶ Extensive oxidation and abrasive wear at 750 °C leads to substantial material loss in hot work tool steel. ▶ The material loss of the AlCrN-coated tool steel is nearly two orders of magnitude smaller. ▶ This is attributed to the adhesive and highly plastic Cr2O3 film that forms on AlCrN coating. ▶ Reduced oxidation suppresses the synergy between oxidation and wear, and improves the resistance to abrasive wear. ▶ Higher hardness of the AlCrN coating is also believed to be instrumental.

Purpose: The objective of the present work was to study the effect of the microstructural banding on the thermal anisotropy of hot-work tool steel used for die for aluminium alloy die-casting. In particular, the major purpose of this research was to find possible correlation between geometrically oriented thermal expansion coefficient values and the presence of number of parallel cracks on the working surface of die. Design/methodology/approach: The studies were performed on the specimens which were cut from the failed prematurely die along the three axes of the coordinate system (X-axe was parallel to the cracks direction). Macroscopic, metallographic, SEM and dilatometric examination were made. Findings: Surface cracks of die are parallel to the microstructural banding orientation. Differences in the values of thermal expansion coefficient determined along the three axes of the coordinate system probably promote cracks propagation direction. Research limitations/implications: Stud...

High temperature abrasive wear performance of X32CrMoV33 hot work tool steel with and without an Al0.61Cr0.39N coating was investigated under three body abrasion conditions. The Al0.61Cr0.39N coating has a remarkable impact on the wear resistance of the X32CrMoV33 hot work tool steel. Extensive oxidation co-occurring with abrasive wear at 750 °C leads to substantial material loss in the latter. The poor adherence and limited ductility of Fe3O4 promote the failure of the thick oxide scale on the tool steel sample impairing its resistance to abrasion at elevated temperatures. The material loss of the AlCrN-coated tool steel, however, is nearly two orders of magnitude smaller. This is attributed to the adhesive and highly plastic Cr2O3 film that forms on the coating and sustains the abrasion. The much reduced oxidation in the coated sample suppresses the synergy between oxidation and wear, and improves the resistance to abrasive wear. Much higher hardness of the AlCrN coating with resp...

Purpose: The objective of the present work was to study the modification of the microstructure of hot-work tool steel X40CrMoV5-1 during the surface modifying by means of laser technology. Design/methodology/approach: The structural mechanism of surface layer development was determined and the effect of alloying parameters and thickness of paste layer applied onto the steel surface on structure refinement and influence of these factors on the crystallisation mechanism of surface layer was studied. Findings: Development of the surface layer was observed in which one can distinguish the remelted zone, heataffected zone and the transient zone. The fine grained, dendritic structure occurs in the remelted and alloyed zone with the crystallization direction connected with the dynamical heat abstraction from the laser beam influence zone. The X40CrMoV5-1 conventionally heat treated steel was used as reference material. Practical implications: Laser surface modification has the important co...

Effects of atmosphere and specimen geometry on thermal fatigue (TF) crack initiation and propagation in a low Si content hot work tool steel X38CrMoV5-47HRC were investigated. The TF specimen’s geometry enhances the uni-axial TF loading conditions. A high frequency induction heating (3 to 4 MHz) is used. A new TF rig, working under air and/or inert atmosphere with reduced PO2 has been set up. The reduction of PO2 results in localized oxidation sites. Whatever geometry and atmosphere conditions, TF cracks initiate exclusively in the oxide layers. Damage mechanisms are environment dependant. Under laboratory air, parallel macroscopic cracks initiate perpendicular to the hoop stress. Under argon and nitrogen, SEM surface observations show that initiated cracks coalesce by zigzagging along crystallographic paths between non-oxidized zones. In-depth crack propagation mechanism is mainly trans-granular. TF crack initiation life under air and in presence of Fe-Al intermetalllics is decreas...

The nitrocarburization of the AISI-H13 tool steel by ion beam assisted deposition is reported. In this technique, a carbon film is continuously deposited over the sample by the ion beam sputtering of a carbon target while a second ion source is used to bombard the sample with low energy nitrogen ions. The results show that the presence of carbon has an important impact on the crystalline and microstructural properties of the material without modification of the case depth.