This paper presents the development of a modified tool steel (X30CrMnMoN13-3-1) specifically designed for defect-free processing via laser powder bed fusion (LPBF) without requiring complex machine modifications. The research addresses the dual challenge of carbon-containing tool steels in additive manufacturing: maintaining wear resistance while preventing cracking. Through optimization of the alloying system—particularly with carbon, nitrogen, chromium, molybdenum, and manganese—and the use of moderate preheating (150 °C), the authors achieved crack-free components with hardness levels up to 57 HRC after appropriate heat treatment.

Additive brazing is a highly advanced process for producing functional and highly durable coatings. By creating a material bond between components through diffusion without the use of flux, dense, wear-resistant, and crack-free layers are formed, which are particularly useful in areas such as wear protection and the reclamation of components. The ability to adjust the coating thickness and hardness makes the process extremely flexible, allowing it to meet the specific requirements of a wide range of applications. Particularly innovative is the ability to precisely and locally braze using laser energy, further enhancing the efficiency and precision of the process. This paper provides an overview of the process, properties of brazed coatings, and applications.

In this paper, oxidation behavior of three hardmetal coating compositions with different Cr 3 C 2 content deposited on 1.4828 (AISI 309) or 2.4856 (Alloy 625) substrates was investigated. Heat treatment was performed in a tube furnace in a slight air flow (2 l/h) in the temperature range 500-900 °C for 2–32 days.

Cold spraying mixed metal-ceramic powders creates metallic matrix composites, but typically achieves low hard phase content in deposits. We investigated this challenge using various hard phases (SiC, diamond, WC, W) with Al and Cu metal matrices. Our results reveal that density difference—not hardness—between components primarily determines deposition efficiency. When using Al with similarly dense materials (diamond, SiC), deposit compositions remained comparable despite hardness variations. However, mixing Al with 50 vol.% of WC or W produced deposits containing 57.9 vol.% and 79.8 vol.% hard phases, respectively. Based on these findings, we established a ballistic theory-based criterion for effective hard particle deposition.

High-pressure die casting (HPDC) is a well-established manufacturing process used in the automotive sector to make high-precision components. The necessity to reduce fuel consumption increases the use of low-density components in the automotive industry. Corrosion induced by molten metal is one of many failure modes for dies, changing the die's geometry and surface roughness. All combined wear changes the dimensional precision of the manufactured parts but also the surface quality of the components. Many additive deposition methods are applied to decrease wear and recover the surface. Thermally sprayed coatings can improve the surface properties and recover the geometry of the die caused by the aluminum attack. The main objective of this work is to observe the behavior of the H13, Cr3C2-25NiCr, and WC10Co4Cr coatings deposited by HVOF and HVAF, tested against Aluminum corrosion and Die-soldering tests. After dissolution, the chromium carbide reacts with the aluminum, creating a tough intermetallic interface, and raising the extraction tensile stress. After Aluminum corrosion tests, it was observed that the WC 10Co 4Cr HVAF coating presented low adhesion to the aluminum with no observed coating failure due to the formation of intermetallic. Die soldering tests indicated that the WC 10Co 4Cr protects the substrate, resulting in lower extraction tensile stress than H13 base material and other HVOF coatings. It was possible to observe that WC 10Co 4Cr HVAF coating showed results comparable to AlCrN PVD coating.

Successful cold spray of tool steels and other hard steels would unlock several opportunities, including the repair of molds as well as ships and heavy industry components. However, the high hardness of typical atomized steel powders strongly limits their cold sprayability. It has been recently demonstrated that heat treatment in a rotating furnace can significantly improve H13 cold sprayability via softening and agglomeration. In this work, this powder modification method is extended to a range of transformation hardenable steels: 4340, SS420, A588, 1040 and P20. The results show that powder heat treatment improves the powder deposition efficiency and the quality of the final cold sprayed coating, probably as the result of the decreased powder micro-hardness. The effects of the powder heat treatment atmosphere, a key parameter, will also be presented and discussed.

In nuclear fusion reactors, the first wall is the name given to the surface which is in direct contact with the plasma. A part of it is the divertor which is a device that removes fusion products from the plasma and impurities that have entered into it from the vessel lining. It is covered with water cooled tiles which have to withstand high temperatures and high heat fluxes. Moreover, resistance to neutron bombardment, low tritium absorption and low hydrogen permeation are additional demands. One materials concept under research is the application of a Reduced Activation Ferritic Martensitic Steel (RAFM) as a structural material with a tungsten protective coating. Since there is a considerable thermal mismatch between, a functional graded materials (FGM) concept was proposed. As the formation of undesired intermetallic Fe-W phases as well as oxidation should be avoided, cold gas spraying was chosen as manufacturing process. Two powder blends of EUROFER97 RAFM steel and a fine tungsten powder cut on the one hand and a coarser one on the other hand were tested in different ratios. The coatings were characterized with respect to their porosity and surface structure. Furthermore, the deposition efficiencies for steel and tungsten were determined each. It turned out, that the deposition process is a complex mixed situation of bonding and erosion mechanisms as the deposition windows of these very different materials obviously diverge. Thus, a lower working gas temperature and pressure was advantageous in some cases. Unexpectedly, the coarser tungsten powder in general enabled to achieve better results.

Process monitoring and control methods during direct metal deposition (DMD) are used to ensure a consistent manufacturing quality of the process. In the optical regime, naturally occurring process emission provides therefore selective and specific element lines, which can be obtained by optical spectrometers. However, DMD processes are in the heat conduction regime and superimposed broad spectral emissions dominate the wavelength specific signals. The aim of this work is to investigate the occurrence of different elemental lines in DMD processes as well as deposition track cross-sectional dimensions. Therefore, experiments were simultaneously conducted by using a high-resolution spectrometer (resolution = approx. 47 pm FWHM at 522 nm and 55 pm FWHM at 407.5 nm) and a medium resolution spectrometer (resolution = 0.73 nm FWHM), which were coupled by a bifurcated optical fibre. A parameter study of 27 single track DMD experiments using Co-Cr-based (MetcoClad21) powder on low-alloyed tool steel C45W (1.1730) substrate material, varying laser power, scan velocity and powder feed rate was conducted. Series of spectra were obtained for all sets of parameters with a scan rate of 100 Hz. The individual wavelength spectrum was analysed and classified by an algorithm into two types. Type-A spectra, with specific element emission lines and Type-B spectra, without significant emission lines with mostly predominant thermal emission radiation. Each deposition track was coupled to cross-sectional dimensions, including height, welding depth and melted areas. In addition, certain elemental lines contained in Type-A spectra were verified by using data from the NIST atomic spectra database. The investigation indicates that the relative number of Type-A spectra with respect to the total quantity of spectra, correlates significant to the process parameters. All detected and identified element lines occurred to be non-ionised elements, especially Cr I, Fe I and Mn I lines were frequently observed.

A novel powder modification method based on the simultaneous softening and agglomeration of steel powders via heat treatment in a rotary tube furnace has been investigated as a means to improve the cold sprayability of H13 tool steel powder. By adjusting starting powder size and shape as well as heat treatment conditions (maximum temperature, cooling rate, and atmosphere), cold spray of H13 powder went from virtually no deposition to the production of thick dense deposits with a deposition efficiency of 70%. Powder agglomeration, surface state, microstructure evolution, and softening are identified as key factors determining powder deposition efficiency and resulting deposit microstructure.

Nickel-aluminum alloys are widely used in harsh environments due to their corrosion resistance, high melting temperature, and thermal conductivity. In this work, Ni-5wt%Al coatings were deposited by twin-wire arc spraying (TWAS) on tool steel using a design of experiments approach to study the effect of process parameters on coating microstructure and performance. Test results presented in the form of process maps show how N2 pressure, stand-off distance, and current affect in-flight particle velocity and temperature as well as coating thickness and oxide content. Using this information, optimized coatings were then deposited on test substrates and subjected, along with uncoated tool steel, to several hours of molten aluminum attack. The coated samples showed no signs of physical or chemical damage, whereas the uncoated substrates experienced oxidation, aluminum infiltration, and formation of Fe-Al intermetallics.

A common method to combat abrasive wear and prolong the life of a component is to hardface the exposed region by overlay welding. State of the art coatings for these applications consist of a nickel-based ductile matrix with hard tungsten carbide particles embedded in it. An alternative with low environmental impact in combination with high performance to cost ratio is to use iron-based alloys. Critical in affecting the abrasive and impact wear resistance of these alloys is the coating quality e.g. porosity, cracks, dilution from the substrate combined with chemistry, size and volume fraction of the hard phase particles formed during solidification. Selection of the process parameters is critical for producing sound clads with expected properties. This paper focuses on the properties of PTA welded and laser cladded M2, M4 and A11 high speed steel coatings. Clad quality, hardness, abrasive wear resistance and microstructure are presented and interpreted with support of thermodynamic simulations.

An ultrasonic nanocrystal surface modification (UNSM) technique was applied to the thermally sprayed yttria-stabilized zirconia (YSZ) ceramic thermal barrier coating (TBC) deposited onto a hot tool steel substrate to improve the mechanical and tribological properties. The surface microstructure of the as-sprayed and UNSM-treated coatings was examined using a scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Raman spectroscopy, while the hardness of the coatings was measured by Vicker`s hardness tester. The friction and wear behavior of the coatings was assessed using a ball-on-disk tribometer against bearing steel (SAE52100) ball at temperatures of 25 °C and 200 °C under dry reciprocating conditions. Results showed that the UNSM-treated coating had smoother surface, lower friction and higher resistance to wear compared to that of the as-sprayed coating. It was found that hybrid use of thermal spray coating (TSC) and UNSM technique is meaningful to bring together synergy effect of two emerging surface technologies.

High-temperature tribology plays an important role in many engineering applications such as metal forming operations and aerospace industry. Several problems in hot-metal forming of high strength steels occur such as oxidation of tool and workpiece surfaces, increased wear of tools and scaling of workpiece. Moreover, operations at elevated temperatures can significantly influence frictional behavior of tool steels. Present research attempts to analyze experimentally and understand tribological behavior of AISI H11 and AISI H13 under dry conditions at room temperatures. High velocity oxy-fuel (HVOF) thermal spray NiCrBSi coating was developed on tool steels. The room-temperature wear performance of uncoated and coated tool steels was evaluated on pin-on-disc tribometer in the laboratory. In-depth analysis of exposed as-sprayed samples was examined with X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS).

The objective of this study is to investigate the feasibility of high velocity oxy-fuel (HVOF) spraying of tool steel coating containing high boron and high carbon. A full factorial experimental design was established to investigate the influence of process parameters on the coating formation. The microstructural investigations revealed that the tool steel containing ultrahigh boron and high carbon can be coated using HVOF. The coating microstructure does not seem to be conventional lamellar structure and consists of high density micro-cracks. However, the coating features superior hardness of about 980 HV and shows the potential for wear resistance applications.

Multilayer high-speed cladding by injection of a M2 steel powder with 0.82%C, 4.7%Mo, 6.4%W, 4.1%Cr, 2.02%V, 0.3%Mn, as chemical composition, in a melted bath produced using a CO 2 continuous wave laser connected to a x-y-z coordinate table was tested in order to increase the wear resistance and heat stability of tool active surfaces made of 0.45%C steel. Layers made by different laser runs were characterized by macro and microstructure analysis, as well as a phase identification analysis by X-ray diffractometry, micro-hardening analysis and hardness testing on the coated layer surfaces in order to establish the optimal cladding condition. Lathe tools made using this technique showed a good ability to maintain their cutting power during steel shaping.

Laser cladding is a novel way to produce metal matrix composites for need of abrasion resistant coatings. There are, however, few comparative studies concerning the choice of reinforcing material and the metallic matrix material. In this study, MMC’s were formed from vanadium-, tungsten- and titanium carbides mixed with tool steel M2, Stellite 21 and NiCrBSi-alloy. The abrasion resistances were tested using rubber wheel abrasion apparatus. The wear surfaces were examined. The best results were achieved by M2 tool steel with vanadium carbides.

Wear resistance of materials in very aggressive environment of different industrial sectors like drilling, mining, cutting, etc, appears to be critical and many efforts have been made to limit the major economic loss that represents a broken or damaged tool. The objective of the CLADIAM project (G5ST-CT-2002-50179) is to develop a cladding technique to coat complex parts based on an innovative cladding material composed of diamond pellets and cast spherical tungsten carbide particles using an automated high power diode laser (HPLD) equipment. The result of these two and a half years of work has led to the finalization of following techniques: A pelletizing alloy that takes into account the constraints of laser cladding, Enrobing of diamond particles to avoid their damage, An industrial technique, technically and economically efficient, of laser cladding that allows the realization of complex shapes. The combination of a new technique of wear and abrasion tests has led to the characterization of the obtained cladding. The results have been compared with the tests on industrial parts in severe and even extreme wear conditions. The development of this new cladding technology has been possible thanks to the use, the characterization and the optimization of specific cladding nozzles associated with the special beam of high power diode laser. The results obtained are very encouraging and open the doors to new claddings that combine the specific advantages of diamond and tungsten carbides for the nature of cladding, but also the fineness of the structure, the improvement of behaviour in wear conditions, the small thermal impact of the parts, some of the well known advantages of laser cladding.

WC-Co and WC-CoCr coatings were deposited with the JP-5000 liquid fuel HP/HVOF system using various thermal spray powder types. The microstructure, microhardness, deposition rate and wear resistance of the coatings were characterized. The results show that these coatings provide significantly more protection from dry three-body abrasion than from dry sand erosion, when compared to mild steel. They also provide more advantage at low angles of erosion than at high angles of erosion. Furthermore, the coating composition was found to have a significant effect on the wear rates, with WC-CoCr providing the best wear resistance even after taking the higher cost of the powder into account. The powder manufacturing route had only a secondary effect on the wear rates, except in the case of fused and crushed powder, which produced an inferior coating.

Tungsten caibide (WC) thermal spray coatings are being used for wear protection on selected components of aircraft. Tungsten carbide coatings are being used on aircraft flap tracks and fan and compressor blade mid-span dampers. However, a larger use of tungsten carbide coatings is being considered for other commercial aircraft applications where it would be used as a replacement for chrome plating. For instance, WC coatings are currently being tested on aircraft landing gear parts. One factor that affects the suitability of WC coatings for these applications is the fatigue life of the coated part. Coatings, whether chrome plating or thermal spray coating, can reduce the fatigue life of the part compared to an uncoated part. This study compares the fatigue life of uncoated 6061 aluminum specimens to the fatigue life of WC thermal sprayed coated 6061 aluminum specimens. The relation between the residual stress level in the coating and the fatigue life of the specimens is also investigated. Fatigue tests were run on cantilever flat beam specimens that were coated on one side. Specimens were cycled in bending so that the coatings experienced tensile fatigue stresses. Residual stress levels for each type of coating were determined using the Modified Layer Removal Method on specimens processed along with the cantilever flat beam specimens. Test results show that the fatigue life of the WC coated specimens is directly related to the level of compressive residual stress in the coating.

WC-Co-Cr powders with different WC particle size have been sprayed by the HVOF process. At constant spraying conditions the powders give coatings of different quality. The deposition efficiency during spraying of powders containing large WC particles was found to be low compared to powders with finer WC grains. In addition the amounts of porosity and cracks were different. The coatings have been characterised by different methods. Erosion and erosion-corrosion tests showed that the WC particle size also influence the wear resistance of the coatings. Small WC particle size was found to be beneficial. Chemical composition of the matrix was also found to be decisive for the coating properties. An increase of the chromium content improved the erosion-corrosion resistance.