Extreme High -Speed Laser Cladding (EHLA) is a new process category of laser cladding. In this study, EH-LA layer was characterized by comparing with conventional laser cladding (LC) layer. Basic SUS316L layers, as well as WC-reinforced SUS316L layers, were formed on SUS304 substrates using both LC and EHLA processes. The macroscopic morphology, microstructure, microhardness, wear resistance, and residual stress of the four types of layers were evaluated. As a result, EHLA layers exhibited slightly higher micro-hardness and less wear loss than that of LC layers, despite the presence of more micropores. This can be due to their finer dendritic structures. Furthermore, residual stress of EHLA layer was lower than that of LC layer due to those micropores. Additionally, EHLA can add up to 45 wt.% WC into SUS316L layer without crack formation, resulting in higher wear resistance than that of LC where crack formation occurred at 25 wt.% WC. This enhanced crack resistance in EHLA is believed to be due to the less heat input during deposition.

Laser cladding is a technology that uses high-energy-density lasers to quickly melt and solidify alloy powder on the surface of the metal substrate to form a cladding layer with good performance. Especially, martensitic stainless steel is widely used as a cladding material due to its high hardness and wear resistance. In this work, the martensitic stainless steel layers were fabricated on the C45 steel substrate by the laser cladding with different process parameters. The results show that holes in the cladding layer is unavoidable. The laser cladding process parameters have the important influence on the residual stress in the cladding layer. Under the action of residual stresses, the holes in the cladding layer will be the source of cracks, which will cause cracks in the cladding layer.

The purpose of this work is to study the effect of laser radiation on powder particles transported by gas during laser cladding. The temperature and velocity of particles entering the light field of a CO 2 laser were determined by measuring particle radiation as well as the scattered radiation of the diode laser, two independent methods. It is shown that under the action of laser radiation, the particles acquire additional acceleration due to the vapor pressure from the irradiated part of the particle surface. This sonic recoil vapor pressure can significantly affect the in-flight characteristics of powder particles in a gas jet. Particle velocities due to laser acceleration exceeded 100 m/s in a carrier gas with a flow rate less than 30 m/s. Particle temperature depends on several factors and was found to vary from ambient temperature to the boiling point of the powder.

Laser cladding offers several advantages as low dilution, low thermal influence and distortion of the components and a fine microstructure due to the high cooling rate. Nevertheless the set of laser cladding in the industrial production is nowadays limited to few applications, as the efficiency of laser sources is still too low and the running costs are too high. The absorption behaviour of metal surfaces, as for example steel, towards diode laser (up to approx. 42%) is very high compared to Nd:YAG (approx. 35%) and CO 2 -Laser sources (approx. 11%), so that some benefits can be expected. One of the disadvantages of diode laser was the low intensity and the difficulty to couple it in a fibre. The development of the last years reached to overcome these boundaries. High power diode lasers are nowadays available till 6 kW and can be coupled in fibres, allowing an easier processing. Investigations regarding laser alloying with high power diode laser confirm the appreciable reliability of this laser class. In order to improve efficiency of laser surface processing the hybrid process plasma-augmented-laser-cladding (PALC) with an Nd:YAG laser source was presented and confirmed that due to the pre-heating of the powder through the plasma transferred arc and the activation of the metallic surface a higher processing velocity (factor three) and efficiency could be reached by summing only one third of the energy with a PTA-equipment. Further more when processing with higher velocity the energy loss due to conductivity decreases so that a further positive increase of efficiency can be depicted. The suitability of fibre coupled high power diode laser for PALC hasn’t yet been investigated, even if the set of this laser type would be very advantageous. In this paper investigations regarding the process design and the necessary set up of the hybrid PALC-process with a 3 kW fibre coupled high power diode laser and wire coating metal are reported.

The economic efficiency of spraying a frequently changing spectrum of parts is strongly dependent on the costs of planning the spray process. In many cases, the robot program for coating a three-dimensional surface is generated directly on the control unit computer. Programming results in costly downtime. At IWS, a technology for off-line programming of robots and CNC systems for thermal spraying (TS) and laser cladding (LC) was developed. Coating programs are developed using CAD data from a workpiece and checked with simulation software. All steps are accomplished off-line without influencing ongoing production. Off-line programming of spray processes for three-dimensional surfaces enables substantial time savings to be realized, more so with increasing part complexity. These programs enable a constant spray distance and traverse speed as well as a permanent spray angle of 90° to the substrate to be achieved.

Laser cladding technology is widely used in industry to precisely apply tailored surface coatings, as well as three-dimensional deposits for repair and additive layer-by-layer fabrication of metallic parts. However, the processing of larger components, like tools for oil and gas production, is economically challenging due to the conventionally low deposition rates. Consequently, industry is requesting more powerful technologies that maintain the quality advantages of the laser technology, but also make the process more productive and time effective. The modern highest power diode lasers offer practical solutions for applying of large-area laser cladding with significantly increased productivity. Using a fiber-coupled diode laser of 20 kW power and the accordingly developed laser cladding heads, real deposition rates of metal alloys, e.g. Inconel 625, could reach 14 kg/h. With the new-developed powder nozzles with rectangular profile of the powder jet allows at a laser power of 20 kW single tracks with 45 mm-width can be produced. Besides the laser source, the processing laser head is the key parameter for a high productivity and efficiency of the whole cladding procedure. The paper presents a new generation of high-performance laser cladding heads with integrated process sensors, which guarantee a stable long-time operation at highest power levels. The deposition rates achieved with this technology are equal or even exceed typical values of the common PTA technique. Current applications are large-area coatings on power plant components, hydraulic cylinders for off-shore equipment, and large metal forming tools for automotive bodies.

The potential of additive manufacturing has reached a point where the techniques are considered highly relevant for production purposes. In general, the manufacturing industry greets the new approach with enthusiasm, as it offers innovative designs and potentially reduced production costs. However, questions arise concerning the durability of additively manufactured components. This paper describes industrial trials with laser cladding and precipitation hardening heat treatment of thin-walled structures with the 17-4 PH stainless steel alloy. Due to the great relevance of the AM production methods for the aviation industry, the mechanical strength of the alloy given by the MMPDS document is used as a baseline. In order to improve the properties of the produced specimens, hot isostatic pressing was applied. The results show that a post processing treatment consisting of a HIP cycle and a conventional precipitation hardening, vastly improves the mechanical strength and elongation values of printed specimens, causing them to exceed the specified values.

This paper describes a method for producing textured surface layers on vacuum chamber components that act as particle traps. The novel textures consist of a stainless steel core produced by direct energy deposit laser cladding covered with a twin-wire arc sprayed aluminum film. The process has been qualified for 20 nm and older IC architectures and is now implemented in production equipment. It has been proven to significantly increase preventive maintenance intervals, reduce particle levels, and enhance yield.

Magnesium and magnesium alloys are the lightest structural materials with an approximate density of 1.7 g/cm³ (density of aluminium ~2.7 g/cm³). Due to the poor corrosion and wear resistance properties, they need to be coated for usage in lightweight constructions. AlSi20 was found to be a suitable coating material to improve the properties of parts made of the magnesium alloy AZ31B. Within this work, coatings are applied by thermal spraying, laser cladding and the combination of both processes. These coatings were investigated regarding corrosion protection in 3.5 % chlorine solution in a three electrode setup to obtain electrochemical corrosion characteristics. Abrasive wear was investigated using a pin-on-disc tribometer and abrasion rate was calculated. Resistance against shock loads was tested by applying a cyclic load at 50 Hz in order to investigate the resistance against impact stresses.

This paper demonstrates the use of two laser cladding automation tools, one that automates laser power and one that automates laser head positioning. Both tools are based on intelligent cameras that evaluate recordings from the cladding zone through the optical path of the laser. The laser power tool monitors and controls local emission from the laser cladding process. The position control tool detects distances between edges on component surfaces and generates an error correction signal based on edge-geometry and material data and various process settings. Examples in which the closed-loop tools are used to clad thin-walled tubes with different alloys and fill irregular grooves on shafts are presented.

In Laser Cladding, a differentiation must be made between cladding by brazing and cladding by welding regarding process parameters and the resulting material properties. Results of investigations of bronze cladding on steel parts produced by Laser Deposition Brazing will be presented. This means that a strong metallurgical bond is realized by diffusion processes by Laser Deposition Brazing, but the steel base material is not molten. The coatings were characterized by hardness distribution measurements from the bronze cladding to the steel substrate, by measuring the size of the heat-affected zone and by porosity measurements. This combination of a steel substrate and a local bronze coating is used industrially in many tribological applications, such as plain bearings or hydraulic pumps etc. The bronze offers excellent tribological properties. In some cases, the bronze is used as a complete solid part. However, applying the bronze locally to a steel base body instead of using a complete solid bronze component, offers the advantage of the higher modulus of elasticity of the steel, which provides greater stability of shape with regard to possible elastic deformations as these coated parts are exposed to high mechanical loads, it is essential that a high coating quality is achieved by laser cladding and that the properties are extensively and purposefully characterized. The production technology, the characterization and the industrial applications of such bronze coated steel parts are presented and explained in this contribution.

Laser cladding shows an increasing interest to apply high-quality tailored surface coatings, as well as 3D-deposits for repair and additive manufacturing of metallic parts. The industry is requesting powerful technologies that maintain the quality advantages of the laser technology, but also make the process more productive, as well as time and cost efficient. At Fraunhofer IWS a Laserline fiber-coupled diode laser of 20 kW power has been employed for over a decade to develop competitive coating solutions. The deposition rates achieved with this technology are comparable to those of common PTA technique, while at the same time bringing significant advantages in terms of reduced heat affected zone, distortion and savings in material resources.

This work focuses on the laser cladding process and the behavior or interaction between the powder particles and the laser beam, specifically examining how various process parameters might affect the creation of melt pool formations. The experiment focused on examining the influence of laser intensity and other important factors on the amount of metal in the substrate of 316L stainless steel, particularly while utilizing Inconel 625 powder. The study was conducted by utilizing cross-sectional images and quantifying the ratio of areas of the melted substrate material across a sliced cross-sectional area. The study also investigated the influence of recirculation patterns resulting from the Marangoni convection force on the formation of the melt region. The study's results indicate that a low powder feed rate is preferable, which in this study was 5 g/min, and provides better results with a symmetrical and profound melt profile. The melt shifts to asymmetrical profiles when the feed rate increases significantly over this value. The primary cause of this phenomenon is attributed to the Marangoni forces and the momentum transfer generated by the powder jets. The investigation also emphasizes the complex interplay among the process factors and highlights the crucial role of laser source power in triggering a fast escalation in the volume of melted material. In addition, the study supports the idea that maintaining the laser energy input as a constant helps to create a consistency in the total melt area even when the cladding speed is increased.

In glass mold industry, a surface treatment by laser cladding of a Ni based powder on cast iron is performed with a 4-kW continuous diode laser. For this, a robot programming method named "Wavering" was used. This method allows to cover large surfaces (higher than 5 mm). The cast iron substrate used during this work is employed for its heat exchange properties in glass mold Industry. However, it has drawbacks which are weak wear, corrosion, and abrasion resistance. Conventional techniques used to protect the molds, like Plasma Transferred Arc (PTA), affect the molds microstructure, but also the thermal and mechanical properties. The laser cladding of the Ni based alloy allows to protect the molds without affecting the cast iron thermal properties (and reduce the Heat Affected Zone length). The purpose of this research is to produce a well bonded Ni based melted powder without pores or cracks on large and curvilinear surfaces with the wanted geometry. The impact of the process parameters such as laser power, scanning speed and frequency on the coating geometry was investigated with an experimental design technique using the ANOVA (Analysis of variance) method. It was used to determine and represent the influence of each process parameter on the coating geometry (width, height, and circularity). This ANOVA analysis led to a parameter combination to optimize the Ni coating and the cast iron substrate quality by considering the industrial geometrical constraints. The bonding quality and the cracking behavior are also investigated on optimized parameters. Finally, it appears that laser cladding process leads to a better coating on curvilinear surfaces than other process like PTA.

Laser-induced surface acoustic wave spectroscopy (LISAWS) allows quick and non-destructive access to elastic properties such as the Young's Modulus of coatings, surfaces and surface-near bulk materials. Furthermore, the mechanical weakening due to cracks and pores can be evaluated, as they influence the propagation of surface waves as well. Therefore, the method is a quick and powerful tool for surface characterization and can be found today in research and development, quality control and as a precise reference method. The short measuring time of the LISAWS measurement allow the distribution of the effective Young's modulus over the coated surface to be determined with a high accuracy. For this purpose, a LISAWS measurement system was automated to allow for processing of a larger amount of samples and fast mappings. The investigated coating materials were thermally sprayed Al 2 O 3 insulation coatings and WC-reinforced 316L steel coatings on brake discs produced by laser cladding. For the Al2O3 coatings, the correlation of the Young's modulus and its areal distribution is shown for different process parameters, such as spray gun movement direction or spraying distance, and compared with results from pull-off tests. For the WC/316L coated brake discs, the distribution of the wave velocity over the coated surfaces or the two coated sides of different discs with varying coating qualities is used to assess the coating quality and homogeneity.

The development of materials and alloys for coatings has been increasingly important for reducing costs in different manufacturing processes. The Inconel alloy is widely used due to its chemical inertness and high resistance to high temperatures, but it does not present adequate resistance to erosive wear. In this context, the resistance to wear from cavitation erosion and slurry erosion was evaluated of samples with depositions obtained by laser cladding (Laser directed energy deposition - L-DED) of Inconel 718 and Inconel 718+10%NiNb. The cavitation erosion wear tests were carried out following the ASTM G32 standard (2016), and the ASTM G73-10 standard (2017) was used to evaluate the resistance to slurry erosion wear. The scanning electron microscopy technique (SEM-EDS), and X-ray diffraction (XRD) were used to characterize the cross-section and the surface after wear. The wear mechanism was checked and identified. Microhardness profiles of the cladding cross-section were carried out. The mass loss and wear rate due to cavitation and slurry jet erosion of Inconel 718 and Inconel 718+ 10% NiNb coatings were determined. It was proven that the addition of 10% NiNb in the formation of the cladding caused a 45% increase in average microhardness in the cross-section of the Inconel 718 cladding. The addition of 10% NiNb to the Inconel 718 cladding caused a decrease in mass loss due to slurry erosion from 38.9 mg to 21.9 mg (33%) when the erodent impact angle was 60°.

This study investigates the influence of laser cladding parameters on the geometry and composition of metal-matrix composite (MMC) coatings. Composite coatings are made of a Ni-Cr-B-Si metallic matrix and of WC reinforcement with a volume fraction of 50 %. Optical microscopy is used to characterize the coating geometry (height, width and penetration depth) and to determine the real volumetric content of WC. Laser cladding on low carbon steel substrate is carried out using a cw Nd:YAG laser, a coaxial powder injection system and a combination of Taguchi and EM methods to design the experiments. This combination explores efficiently the multidimensional volume of laser cladding parameters. The results, which express the interrelationship between laser cladding parameters and the characteristics of the clad produced, can be used to find optimum laser parameters, to predict the responses and to improve the understanding of laser cladding process.

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.

In order to increase the wear and corrosion resistance of 0.45% C surface steel layers, a multilayer coating was tested by injection of a powder with 8.9% Cr, 4.5% Fe, 5.1% B, 2.4% Al, 0.6% Cu and all remainder of Ni in the melted bath produced using a CO 2 continuous wave laser. To determine the optimal melting regime, the layers obtained by different laser conditions were characterized by macro and microstructure analysis, as well as a phase qualitative analysis by X-ray diffractometry and microhardness analysis.

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.