The H-class turbine, introduced nearly a decade ago, has reached a significant milestone with its 100th global sale. With 108 units sold and 91 in operation across four continents, accumulating over 3.2 million fired hours, the SGT5-8000H has established itself as a market leader, setting industry benchmarks for performance. Since its launch, the SGT5-8000H's output has increased from 375 MW to 450 MW, and combined cycle efficiency has surpassed 62%. To maintain optimal performance, the platform combustion system (PCS) of the SGT5-8000H has undergone refurbishment in Berlin since 2017. Beginning with a PCS from Samsun, Turkey, the process involves a detailed inspection, repair, recoating, and final assembly. Advanced technologies, such as blue light scanning, enhance efficiency and enable lifecycle assessments. Innovative repair methods, including 3D printed patch repairs using laser powder bed fusion (LPBF), reduce costs. Laser-based cutting and welding automation further minimizes heat input and distortion, ensuring the PCS's reliability and longevity. These technological advancements contribute to the SGT5-8000H's stable and dependable operation.

The objective of this work is to assemble an aluminum alloy to a steel to reduce the final mass of this assembly. Doing that, cold spray is considered as an efficient solution. Surfaces are previously prepared with a texturing laser to improve the adhesion of the coating on the substrate. Deposits are slightly rough (Ra < 10 μm), porosity is less than 1% and adhesion is higher than 80 MPa for textured surfaces. These high values are also due to the high filling rates in holes (100% for steel and 65% for aluminum alloy). Shear values obtained through the combination of laser texturing and cold spray for multi-material assembly are of 90 MPa (a heat treatment of 3h at 300°C applied on the joining point improves mechanical strength and increases it by three). By analogy with linear joining methods such as Laser Welding (190 MPa), the values obtained in uniaxial tension by this assembly method are significantly lower (around 50 MPa). It can be explained by the nature of the joining bead, which is made of aluminum alloy.

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.

The degradation of pump components by corrosion and complex damage mechanisms, e.g. erosion and cavitation leads to high costs through replacement and maintenance of parts. To increase the lifetime of cost-efficient components with superior casting properties, gray cast iron parts are surfaced with duplex stainless steel using an inert shielding gas metal arc welding process. The dilution of the surfacing increases with both increasing heat input and increasing thermal conductivity of the shielding gas. The microstructure is highly affected by the cooling conditions that may enhance diffusion processes and eventually lead to precipitation of deleterious carbides. Higher heat input and prolonged cooling duration during surfacing lead to high dilution and a pronounced carbide network and thus, substantially reduced corrosion resistance in artificial seawater. The corrosion of the surfacings in the potentiodynamic polarization test is driven by selective corrosion of the phase boundary between carbides and chromium-depleted austenite. Passive behavior is observed for coatings with low dilution and higher cooling rates, which showed homogeneous chromium distribution and no interconnected carbide networks. In conclusion, the corrosion behavior of gray cast iron was improved by surfacing with duplex stainless steel.

Highly wear resistant overlays for abrasive environments can be provided by welding technologies such as Plasma Transferred Arc Welding (PTAW) or Laser Cladding. Therefore, these overlays can contain higher amounts of hard particles with a desired homogeneous distribution through the weld overlay, all embedded in a metal matrix. Depending on the welding technology, the dissolution of the hard particles has to be considered as result of heat input and chemical reaction between hard particles and metal matrix while welding. Cast Tungsten Carbides (CTC) in self-fluxing Ni based alloys are widely used and accepted compositions and allow to target requirements such as hardness, impact toughness and/or corrosion resistance if required. This investigation compares CTC with Macroline Tungsten Carbide regarding abrasive wear resistance in Ni, Co and Fe based alloys applied by PTAW and Laser cladding and gives an outlook on potential new solutions for wear resistance in abrasive conditions. Beside the relative wear resistance, this investigation also focusses on the seam thickness as reaction zone between the carbide particles and the metal matrices. A first SEM and EDX analysis of a worn surface and precipitated phases provides an explanation regarding wear behavior in abrasive conditions.

Stellite 6 is a widely applied hardfacing alloy with good corrosion and wear resistance. Several different techniques have been used to deposit this alloy, like oxyacetylene, Tungsten Inert Gas welding overlay, CO 2 laser cladding and thermal spray methods. This paper evaluates the wear and corrosion resistance of Stellite 6 coatings applied by high velocity oxygen fuel (HVOF) spraying and gas tungsten arc welding (GTAW) hot wire technique. Mechanical properties and microstructural characteristics of the coatings are assessed and compared. The influence of these properties in the wear results is further discussed.

In order to improve the wire arc spray process an inverter power source (PS) from gas metal arc welding (GMAW) process was used to evaluate the influence of current modulation on the formation of coating particles. Using the inverter PS allowed the application of high current pulses with varying amplitude and frequency. It was shown that particle formation can be limited to the high current phases, and that a strong interaction with the gas flow can be observed. The investigations suggest that using this technology new parameters may be introduced to control the wire arc spray process.

The purpose of this study is to determine if a GTAW (TIG) repair weld under an APS ceramic coating would cause a reduction in adhesion strength. Two stainless steels and a titanium alloy were selected for the study. For each material, 300 buttons were machined and further processed in groups of 50 through the application of one-pass, three-pass, or full pad welds. Welded buttons were lapped parallel to within 0.0002 in. and their lengths were compared with measurements obtained from buttons that had not been welded. NiCrMo bond coats were applied by HVOF spraying to both welded and unwelded samples, which were then top-coated with a ceramic layer (Cr 2 O 3 , Cr 2 O 3 -Al 2 O 3 , or TiO 2 ) deposited by air plasma spraying. A ten-cycle heat treatment was conducted on half of the samples to determine if the weld would amplify thermal expansion stresses. Based on adhesion test results, the welding had no measurable effect on adhesion strength nor did the heat treatment. Heat input from the HVOF flame and the plasma jet was sufficient to reduce weld-related solidification stresses.

This work evaluates the potential of using twin wire arc (TWA) spraying as an alternative to metal active gas (MAG) overlay welding in the production of agricultural equipment. Corthal 65, a flux-cored wire electrode, was applied to different types of steel using each method. Some of the samples were tested in a lab and some were evaluated under actual use in the form of plow tips and harrow teeth. SEM and EDX analysis revealed the presence of Cr, Nb, and W carbides and Al-rich oxides in the hardfacing layer. Field-tested samples were assessed based on porosity and hardness, providing a measure of abrasive wear and impact resistance. The TWA-sprayed coatings performed as well as the MAG overlay welds, but their potential to improve productivity and reduce costs make them the more appealing option.

This work evaluates and compares the properties of weld overlays and thermal spray coatings produced using different feedstock materials. The mechanical and metallurgical characteristics of the coatings and their performance in corrosion and wear tests are discussed.

The main objective of this study is to compare the wear resistance of coatings obtained by gas metal arc (GMA) welding, wire arc spraying, and high-velocity oxyfuel (HVOF) spraying. Tungsten and chromium carbide (WC-Co and CrC-NiCr), iron alloy (Vecalloy B and 140-MXC), and 420 stainless steel coatings were deposited on low carbon steel substrates by the appropriate method. The coatings were examined by optical and scanning electron microscopy, showing no signs of spallation nor relevant level of defects. WC-Co coatings obtained by HVOF spraying exhibited the best abrasive wear resistance. Nanostructured Fe-alloy coatings applied by wire arc spraying performed almost 50% better than HVOF sprayed CrC and only 15% worse than WC-17Co. The erosion resistance of the two WC-Co coatings was very close, although WC-12Co was slightly better possibly due to its higher microhardness, lower porosity, and higher residual compressive stresses.

This study ranks a number of common thermal surfacing materials for soil tillage applications based on the results of dry-sand rubber-wheel testing for abrasion resistance. Test specimens were prepared by plasma transferred arc (PTA) and powder welding deposition of a nickel-based self-fluxing matrix with and without tungsten carbide (WC) additions. For comparison, PTA coated M2 tool steel and quenched and tempered spring steels were also tested. PTA and PW deposition produced coatings with a similar level of abrasive wear resistance. Hardfacing with M2 and nickel-based 1560 deposited by PTA showed ~30% and ~15% wear respectively compared to the reference steels, while nickel-based grades with additions of 50% carbide showed only ~5% wear. Moreover, by increasing the amount of WC from 50 to 60 wt%, abrasive wear resistance was increased by 25%.

Earlier works have demonstrated that Fe2B-based arc-sprayed coatings and weld overlays present outstanding dry erosion resistance when compared to other carbide-based coatings and overlays. The present work was undertaken to examine their wear resistance, particularly their slurry erosion resistance. Cored wires containing chromium (2-20 wt%) and carbon (0.2-1.2 wt%) additives were deposited by arc spraying and gas metal arc welding (GMAW). The abrasion, particle erosion and slurry erosion resistances of these (Fe-B-Cr-C) coatings and overlays were evaluated in laboratory. The results demonstrate that both differences in cored wire composition and variations in the deposition process must be considered in order to obtain the best wear properties.

The attachment hooks of training missile wings are worn out. A technology must be found to repair the hooks. The hooks cannot be replaced. They are made of annealed steel of approx. 50 HRC hardness. A similar hardness should be achieved by the repair procedure without changing the basic material in its hardness and strength characteristics through heating. Additional annealing of the assembly is not possible due to its size. To find a solution to this problem, the cold gas spraying procedure was tested first. Cold gas spraying is a highly kinetic coating procedure in which powdery metal particles are strongly accelerated using inert gases at pressures of up to 40 bars and gas velocities far beyond 1000m/sec. When the particles hit the component surface, they form compact, strongly adherent layers of very low oxide content without preceding melting. As a second procedure, manual laser welding was tested using an Nd:YAG laser under a microscope with filling material. In this procedure, a weld pool can be generated within a few milliseconds. Due to the high velocity with which the energy is applied to the material and absorbed by it, a physical reaction is almost ruled out due to its thermal conductivity. Both procedures have the following advantages: function-related composition of the material applied is possible; the characteristics of the base material are not changed due to the low heating levels; and repeated treatment is possible. This paper compares the results of the procedures and discusses the limits of the technology for this specific application.

Several model Fe- and Ni-based alloys with increased content (up to 30 at.-%) of protecting scale forming elements were developed. High temperature corrosion resistance of bulk alloys as well as thermally sprayed coatings and welded overlays were investigated under the waste power plants simulated atmosphere (500 °C, 100 hours, 75N 2 -20O 2 -4.9Ar-0.1Cl 2 ). Arc and HVOF spraying as well as PTA overlay welding were used to produce the coatings. After an exposure the samples were examined with electron probe micro-analysis (EPMA). It was shown that the protection behaviour of overlay welds depends on the content of alloying elements, although the last is limited because of weldability decrease by high alloying level. High temperature corrosion resistance of thermally sprayed coatings is determined by their porosity, which can be varied over a very broad range depending on the applied spray method. The arc sprayed coatings need an additional post-treatment to close a porosity. Two methods were applied, pre-oxidation treatment in the air and sealing with the commercial sealant. Newly developed iron-based coatings with increased aluminium content (< 20 wt- %) sprayed with HVOF-spraying with powders obtained by means of high energy ball milling demonstrate high corrosion resistance. Selected coatings were evaluated for 1000 h exposure under chlorine-containing salt deposits at the higher temperature (600 °C).

Conventional processes of gas shielded metal arc welding (GMAW) do not offer directly the possibility for cladding heat sensitive materials such as aluminum with iron-based materials due to intermetallic Al/Fe phases form. This paper deals with the first evaluated cladding results of aluminum components with iron-based nanocrystalline solidifying materials by controlled shielded metal arc welding processes to improve wear resistance. In the present work, the design of experiments and data evaluations are systematically applied to get the first results about the dependence between controlled arc welding process parameters and the iron-based coatings of aluminum substrate. In particular, the effect of the chosen parameters such as wire feed speed, welding speed, frequency and further factors on the heat input, welding penetration, micro hardness, rate of welding penetration and width of intermetallic phases in the interface zone are investigated. Optical and scanning electron spectroscopy provide input for further statistical evaluation. The experiments were carried out using various controlled arc technologies which offer different control over the heat input to the substrates. Different power supplies were used.

Welding of dissimilar materials in particular ceramics to metals is a technical challenge with attractive economical consequences. In this study a ceramic coating was processed by plasma transferred arc (PTA). ZrO 2 –7wt.%Y 2 O 3 powders were deposited on low carbon steel plates and on Ni based alloys layers previously welded on a steel plate. Coatings were evaluated regarding the soundness and features of the metal/ceramic bond. Results showed that the pair ZrO 2 –7wt.%Y 2 O 3 /metallic alloy played a major role on the quality of the processed surfaces determining the effectiveness of the bonding. The presence of Al in the Ni based intermediate layer was detrimental to the adhesion of the ceramic coating. Deposition of ZrO 2 –7wt.%Y 2 O 3 on NiCrFe intermediate layers allowed for a metal/ceramic bond resulting on 3,0mm thickness coatings. Ceramic deposits exhibited cracks, whose features were altered after a stress relief treatment of the substrate (AISI 1020+NiCrFe layer) prior to the deposition of ZrO 2 –7wt.%Y 2 O 3 . Transverse section analysis revealed the presence of second phase particles in the ceramic coating and the diffusion of elements from the intermediate Ni based layer into the ceramic deposit.

In Municipal Waste Incinerators (MWI) considerable corrosion problems of critical components, such as superheater or boiler tubes, are always reported. Especially in modern WTE plants the need of efficiency increase requires operation at higher temperatures, which in turn enhances the corrosion rates. Laser cladding technology was successfully used for the production of anticorrosion and resistant-to-erosion coatings on tubes of superheaters and boilers. Compared to protective coatings produced by flame spraying devices, laser cladding is virtually porosity free and metallurgically bonded to the substrate, ensuring the possibility of bending the clad tubes without any damage such as cracks or spalling. This ability to sustain high deformation rate is absolutely necessary for the construction of superheaters serpentines, opening the door to the production of a whole superheaters assembly protected by a laser cladding. Due to the very low thermal load of the process, if compared to usual GMAW welding, laser cladding allows producing coatings with very low iron content (1-3%) even in a single pass with thickness lying in the range 0.7 -1.0 mm. Therefore laser technology enables to produce high quality coatings with a considerable saving in feeding materials, when compared to conventional GMAW welding where 2.5 - 3 mm thick cladding is necessary to have the same iron content of a single pass laser cladding. In this paper are presented advantages of this new technology and CESI RICERCA facilities for industrial production of MWI superheater and boiler clad tubes by its new automatic diode laser workstation. Results of a campaign of in-plant tests and performances obtained in operation by several laser clad components installed in European MWI plants are also presented.

The specific advantages of TiC as a hard material are its low density, high hardness and the high alloyability of the hard phase - binder metal composite. Currently developed agglomerated and sintered core-rim structured TiC-based powders were intensively studied in the last few years for thermal spray coating solutions. In the work described in this paper two different powders with cubic (Ti,Mo)C and (Ti,Mo)(C,N) hard phases and Ni/Co binder, representing the first and second alloying step for the binary TiC-Ni/Co composite, were used together with mechanically mixed NiBSi powder to produce wear resistant coatings by plasma-transferred arc welding (PTA) and laser cladding. Basic process parameters, coating microstructures and properties are described. Coatings with fine grained hard particles were obtained by both processes, while the coating prepared from the nitrogen-containing powder by laser cladding shows a significant smaller hard particle grain size and increased hardness.

Plasma Transferred Arc (PTA) welded coatings are used to improve surface properties of mechanical parts. Advantages are the high reliability of the process and the low dilution of substrate and coating material. Processing of surfaces by PTA welding is restricted at the time to flat horizontal position. Furthermore industry is interested in the development of strategies for coating with PTA in constraint position as complex 3-D parts could be then easily processed as well. Under commercial aspects, the process design can be optimized in order to increase process efficiency and to reduce heat input during the welding process. Process optimization involves the determination of guidelines for PTA welding in constraint positions as well. Modelling the process gives an alternative to reduce the experimental effort to optimize the welding process. Results of simulation studies of the PTA welding process will be given in the present work. It will be shown, that coating conditions can be optimized by varying plasma gas flow, heat input and heat flow, process speed or powder injection with regard to welding in constraint positions. The defined controlling of the PTA welding allows to modify process management with less experimental effort and to develop coating strategies for processing in different positions. In experimental investigations the developed coating strategies will be confirmed by producing PTA coatings in constraint position as well as complex 3-D parts.