Macro Processing: Surface Treatment and Cladding (LiM 2015)

Additive manufacturing of a deep drawing tool
Hannes Freiße, Jochen Vorholt, Thomas Seefeld, Frank Vollertsen

A new approach to establish sustainable production technology in metal forming is to avoid lubricants. This new green technology is called dry metal forming. In this work laser surface technology by means of laser cladding and remelting was used to asses the surface properties by varying process parameters. Furthermore, the cladding process was applied for additive manufacturing. The target was the generation of a deep drawing tool to form circular cups out of 1.4301 high alloy steel with an inner diameter of 30 mm. Different build-up strategies were tested to realize the near net shape geometry of the tool. Parameter set for the deposition process was investigated. The generated forming tool was successfully deployed to form circular cups.

direct powder deposition, additive manufacturing, deep drawing tool


Influence of a short time heat treatment on the formability and aging characteristics of aluminum profiles
Marion Merklein, Matthias Graser, Michael Lechner

Aluminum and its corresponding semi-finished products are widely used in the automotive industry. However, their formability is low in comparison to conventional steel materials. At the LFT a new approach to enhance the forming limits of precipitation hardenable aluminum alloys was invented. By performing a partial short term heat treatment a local softening of the material and the adaption of the material flow is possible. Due to this, critical forming areas are relieved and premature failure is prevented. After already been investigated in detail for blank material the adaption to aluminum profiles is preferable, because they are increasingly used in car space frames. For a better understanding of the mechanisms of this technology a comprehensive material characterization will be induced. Furthermore, the influence on the different subsequent aging processes (natural, artificial) is analysed. Based on the results, a process window and design rules for the implementation of a local short-term heat treatment on profiles of the precipitation hardenable aluminum alloy EN AW 6060 will be derived.

Keywords: Aluminum profiles; tailored properties; laser heat treatment, ageing process


Laser Surface Treatment of electroless Ni–P-SiC coating on Al356 alloy
Reza Shoja Razavi, Sayed Hamid Hashemi

Electroless Ni-PSiC coatings are recognized for their hardness and wear resistance. In the present study, electroless NiP coatings containing SiC particles were co-deposited on Al356 substrate. Laser surface heat treatment was performed using 700W Nd:YAG pulsed laser. Effects of different laser operating parameters, such as laser scan rate, laser average power and defocusing distance on microstructures were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The results of microstructural characterization indicated that the laser treatment under different operating conditions produced composite coating contained nanocrystallined Ni-based matrix with SiC particles Ni3P, Ni12P5, Ni5P2, Ni8P3 precipitates. The microhardness measurements showed that the hardness of the coating was increased up to 60 percent, due to laser heat treatment,
without effect on base metal.

Keywords: Laser surface treatment, Ni-P-SiC, Al356


Characterization of the effect of laser scribing on the isolation coating of electrical steel
Peter Rauscher, Jan Hauptmann, Jörg Kaspar, Andreas Wetzig, Eckhard Beyer

The demand for high energy efficiency leads to an ongoing development of better material grades of grain oriented electrical steel, which is used as core material in power or distribution transformers. In order to reduce the core losses of the silicon steel after the process of rolling different methods can be used, such as mechanical scratching, plasma irradiation, spark ablation and laser scribing. All these techniques induce mechanical or thermal stress that refines the magnetic domains. Due to the no-contact nature and the ease of integration laser scribing is the most commonly used technology, but with the drawback of laser-induced damage of the isolation layer [1], [2]. In this study the material ablation of the isolation layer due to high power continuous wave CO2 (10.6 μm) and fiber laser beam sources (1.07 μm) was investigated in order to evaluate the damage threshold of the coating with respect to the treatment parameters. The study was performed with the so-called LMDR (Laser Magnetic Domain Refinement) test system to realize industry-related process parameters with spot velocities up to 300 m/s and laser output powers up to 4000 W. The experimental results are combined with material studies to characterize the ablation process related to the difference in the absorption behavior of the material based on the difference in wavelength [3].

Keywords: laser scribing; surface treatment; ablation; silicon steel


Reconditioning of lamellar graphite cast iron parts by means of Laser-Cladding and heuristic-based process parameter adaption
Prof. Dr.-Ing. Claus Emmelmann, Dipl.-Ing. Mauritz Möller

Clad layer based on a two-stage experimental study of laser cladding on grey cast iron, a heuristic approach for the prediction of the process parameters is presented. Different repairing strategies using two Ni-based alloy powders are analyzed in an experimental design. Along this results the correlation of dilution, aspect ratio and the weld seam quality is investigated. The mathematical description of cladding quality under the condition of different dilutions and aspect ratios is used to define the repair requirement. The aim is the identification of the process parameters necessary to produce a good quality weld. Since the clad layer quality depends on various influence factors the direct way of determining the suitable parameters is not a possible solution in many repair applications because of the complex free-
form geometries of the damaged areas, the various material conditions, differing part thicknesses and many more. The influence of the differing part thickness and along with this the different thermal situations in the part are chosen exemplary to show the capability of process parameter prediction by the usage of neural networks.

Keywords: laser cladding, reconditioning, lamellar graphite cast iron, inverse modelling of process parameters


Surface structuring by laser remelting of Inconel 718
André Temmler, Tobias Schmickler, Edgar Willenborg, Konrad Wissenbach

A new approach of structuring metallic surfaces is structuring by remelting with laser radiation (WaveShape). In this process no material is removed but reallocated while molten. This structuring process is based on the new active principle of remelting. The surface structure and the micro roughness result from a laser-controlled self-organization of the melt pool due to surface tension. Up to now basic research has been focused on hot work steel 1.2343 (AISI: H11) and titanium alloy Ti6Al4V, and promising results have been achieved for this materials. Current research and development is now seeking to expand the spectrum of processable materials. Since remelting is a thermally driven process, significant differences between metals are expected due to their thermos-physical properties such as thermal conductivity, absorption coefficient, viscosity, heat capacity etc. The nickel based super alloy Inconel 718 has a wide range of industrial applications, especially for turbine components in aviation and aerospace. The innovative WaveShape process for this material will be investigated within this paper. The procedural principle of the WaveShape process is based upon a sinusoidal modulation of laser power while the laser beam is moved over the surface. We used metallographic cross sections to measure the dimensions of melt pool depth and width as they depend on processing parameters, such as laser beam diameter, scanning velocity and laser power. We also investigated basic interdependencies between structural characteristics (e.g. height) and processing parameters used, such as laser beam diameter, laser power, wavelength of modulation and scanning velocity. The results show that surface structuring by remelting is well suited to process the nickel based super alloy Inconel 718 since structures and process velocities achieved are higher than for the previously investigated hot work steel 1.2343 (H11).

Keywords: surface structuring; Inconel 718; remelting; melt pool; laser surface treatment; material redistribution; no material removal


Reconditioning of HPT Blade Tips
Knut Partes

High pressure turbine blades are exposed to high thermal, corrosive and mechanical load. Todays HPT blades consist of superalloys, commonly nickel base. In order to increase the resistance against oxidation attack, the blades have a corrosion coating and an optional thermal barrier coating. Moreover, cooling holes realize a film cooling for further protection. However, after flight operation the blades don’t have the length as a new part. Due to the wear between shroud and the blade the blades got shorter and a welding buildup is mandatory in a repair shop visit. In order to rebuild the blade tips near net shape an automated laser cladding process can be used. Laser cladding is an overlay welding process in order to build up wall like structures or volumetric bodies. The energy for welding the filler material is delivered by a laser beam. The filler material (commonly consisting of powder) is delivered by a coaxial nozzle. The coaxial nozzle realizes the same quality independent of motion direction. Due to the usage of a laser beam the heat can be introduced highly spatial resolved. Hence, a welding process with comparably low heat input is possible. That allows low thermal distortion combined with highly net shaped structures and a high over-all process efficiency. The requirement to repair welding is an adaptive process that reacts on the individual blade distortion coming out of the flight operation. Therefore, in production every blade is individually measured in the laser cell. Afterwards the program is rotatory and translative matched. This allows an individual automated treatment of every blade. The materials of turbine blades have been further developed towards higher creep resistance. The first blades consisted of polycrystalline material. Afterwards, directionally solidified (DS) materials have been developed. Most of todays high pressure turbine blades consist of single crystal (SX) super alloys. The requirement of welding DS and SX materials make the welding process more difficult. Time temperature regimes and spatial motion control have to be more precise in order to match an even smaller process window. By controlling the laser system it could even be possible to generate SX epitaxial solidification. Hence, the solidifying material has the same crystallographic orientation as the base material.


Influence of Pulse Duration on the Glass Cutting Process
Lara Bauer, Uwe Keller, Simone Russ, Malte Kumkar, Birgit Faisst, Thomas Graf

Glass has recently found increasing importance in industrial markets, especially in the rapidly growing sector of display or cover glass applications for consumer electronics. However, cutting of brittle materials is a demanding process if high quality standards are required. High quality industrial glass sheets with high bending stability require minimal micro -cracks, particularly on the cut edges. Cutting techniques involving mechanical or chemical processes lead to cracks, high levels of waste and therefore high processing costs. Nevertheless, these traditional processes currently dominate this area of industrial manufacturing. In addition, the market trend is towards thinner and hardened glass, whe re challenging demands are placed on the processing tools and mechanical methods fail or produce high reject rates. Therefore a new processing technology is needed. Cutting with ultrafast lasers has high potential for processing brittle materials efficiently without time consuming post-processing operations (Siebert, 2012). In this work the influence of pulse duration on the ablation process is discussed. Following our previous findings that the process parameters, such as scanning speed and average power, have a significant influence on the surface properties, which in turn affect the bending stability of the glass sample (Russ, Siebert, Eppelt, Hartmann, Faisst, & Schulz, 2013), we now investigate the influence of the pulse duration on the process by comparing the applications of pulses with 400 fs, 900 fs and 6 ps duration. The influence of the pulse duration on the ablation threshold of aluminosilicate glass is presented, the occurence of nanostructures and the impact on the quality of the cutting edge is discussed.

Keywords: micro machining, picosecond laser, femtoseconds, processing of transparent materials


Developments on Laser Drilling in Gas Turbine Blades
Thomas Beck, Jens Dietrich

Drilling applications represent about 5 % of the industrial laser materials processing applications. Cooling holes in gas turbines for aircrafts as well as for power plants are one of the main applications. The improvement of productivity has led to several drilling strategies with respect to laser sources (thermal drilling and ablation drilling), the beam handling, beam distribution, and handling of the work piece, all of which contribute to the over-all efficiency of the process and a high productivity.
We present the successful development and implementation of a combination of laser systems with different pulse durations for drilling complex 3D geometries. Additionally an overview on actual fields of development is presented.

Keywords: Drilling, Ablation, Surface Functionalization


Development of a wire based laser alloying process for highly stressed surfaces of hot forming steel tools
Konstantin Hofmann, Matthias Holzer, Stefan Lutz, Steffen Schmitt, Vincent Mann, Florian Hugger, Stephan Roth, Michael Schmidt

The machining of high strength steels for vehicle parts in press hardening processes requires high process temperatures which lead to high tool stresses with huge wear. In order to reduce mechanical wear, a local laser alloying process is developed to increase tool-endurance. Therefore, filler material in form of a compact filler wire is used which ensures higher material utilization as well as an avoidance of decomposition problems in comparison to powder based alloying processes. Moreover a dynamic laser beam deflection is necessary to enable a turbulent flow of melt for a homogeneous distribution of alloying elements. To ensure homogeneous dispersion of the alloying elements in the alloying area as well as uniform mechanical properties of the surface, a process development for wire based alloying processes, like different parameters with oscillating laser beam and compositions of alloying elements is necessary. The development of different beam oscillation frequencies in combination with various wire feed velocities enables a suitable process for an adaption of the surface properties. To reach the material-specific element concentrations for hot forming tool steels, which typically lead to an improvement of mechanical and thermo-mechanical properties and increase the wear resistance, the base material is alloyed with nickel and chromium. Oscillation frequencies between 50 and 400 Hz and oscillation amplitudes of the double wire diameter enable the reentry of the oscillating laser beam into still existing melt pools and a stable alloying process.

Keywords: Laser beam alloying, filler wire material, hot forming steels, adhesive and abrasiv wear, Macro Processing: Surface Treatment and Cladding


Inner walls laser cladding of WC reinforced Ni coatings
Josu Leunda, Carlos Soriano, Carmen Sanz

Thick and hard coatings are widely applied in a substantial number of heavy-duty industrial applications to improve wear and corrosion resistance. The techniques that allow producing depositions of metallic, ceramic or metallic-ceramic mixtures in zones with difficult access, like inner walls of a cylinder, are quite limited. Methods like spin casting, for instance, are successfully applied in parts with cylindrical symmetry. Nevertheless, when parts with more complex geometries have to be coated, new solutions must be applied. The use of laser cladding as a possible alternative for these applications is studied in the present work. Coatings of a NiCr matrix reinforced with hard tungsten carbide particles were produced in internal walls. Carbides with different shape and size were employed in order to find the most suitable candidate for producing defect free coatings with maximum thickness. In order to achieve this goal, the effect of different processing parameters had to be investigated, and the use of preheating and a soft buffer layer was also considered for minimizing the residual stresses produced during the rapid cooling of the coating, from the melting point to the solid state. Liquid penetrant tests were used for detecting eventual cracks of the coatings and optical and electron scanning microscopy, as well as microhardness tests were used for characterizing crack-free samples.

Keywords: Laser cladding; Hardfacing; Wear; Metal Matrix Composites; Tungsten carbides


Laser-Induced Subsurface Modification of Silicon Wafers
Paul Christiaan Verburg, Lachlan Smillie, Gert-Willem Römer, Bianca Haberl, Jodie Bradby, Jim Williams, Bert Huis in ’t Veld

In addition to the processing of transparent dielectric materials, pulsed lasers can be used to produce subsurface modificati ons inside silicon by employing near- to mid-infrared light. An application of these modifications is laser-induced subsurface separation, which is a method to separate wafers into individual dies. We investigated the subsurface modification process using a combination of numerical simulations and experiments. Different wavelengths, pulse durations and pulse energies were tested. We found that subsurface melting of silicon followed by rapid resolidification is the primary material modification mechanism. Lattice defects and transformations to both amorphous silicon and pressure-induced high density silicon phases occurred as a result of the laser irradiation.

Silicon, subsurface, wafer dicing, laser-material interaction, electron microscopy.


Deposition of Corrosion Resistant Alloy on to Low Alloyed Steel using LAAM for Oil & Gas Applications
Guijun Bi, Hui-chi Chen, Bing Yang Lee, Beng Siong Lim

In the oil & gas industry, a large number of components are designed with corrosion resistant cladding in order to prevent premature failures, rapid degradation and chemical induced cracking. Most of the surface components are made of carbon steel. However, in order to protect the inner-surface from erosion and corrosion, they are clad with corrosion resistant alloys including stainless steel and Ni-base alloys. Currently TIG/MIG cladding has been widely adopted in the oil & gas industry. However, there are several issues for TIG/MIG cladding. These include low conformance of the clad, lengthy pre-heating and post-weld heat treatment, as well as excessive post-machining time due to undesirable built up of clad material at intersecting holes. Laser aided additive manufacturing (LAAM) has advantages over traditional arc cladding processes for surface modification and repair. The key advantages include lower distortion due to lower heat input to the base material, higher conformance and clad integrity, less materials, manpower and energy needed. In this paper, deposition of corrosion resistant alloy (CRA) onto low alloyed steel using LAAM was studied. Post heat treatment was investigated to achieve required mechanical properties. The results showed that the quality of the clad CRA can be significantly improved. Pre-heating is not necessary and the post heat treatment time can be reduced 50%. The tensile properties of the deposited material can meet the
specifications for oil & gas applications.

Keywords: Laser aided additive manufacturing; inner-surface; corrosion resistant alloy; mechanical properties;


High speed micro cladding using a high-power single-mode continuous-wave fiber laser and a polygon scanning system
Martin Erler, Robby Ebert, Stefan Gronau, Matthias Horn, Sachsa Klötzer, Horst Exner

High speed micro cladding is a new field of research at the Laserinstitut Hochschule Mittweida (LHM). So far, the investigations have been focused on high rate micro cladding with high power short pulse laser s and fast galvanometer scanner systems. Thereby, a high build-up rate of more than 3,500 mm³/h and a structural resolution of 50 μm have been achieved [1, 2]. Laser micro processing e.g. welding and cutting by applying high brilliance laser radiation of continuous wave (cw) lasers in combination with ultrafast beam deflection systems has been successfully applied at LHM [3, 4]. Therefore, the current investigations deal with the potential of high speed micro cladding of μm-sized metal powder using a cw laser. For the experiments, a cw fiber laser with an output power up to 3 kW and a polygon scanning
system for fast laser beam deflection with a scan speed up to 500 m/s are used. Furthermore, to switch the laser irradiation during the scan line, an acousto-optic modulator with a maximum frequency up to 2 MHz is applied. Generated micro-walls and the results of the rapid surface coating with layer thicknesses in the micron range are presented depending on the various laser parameters. Also, the influence of process limits of the high speed micro cladding are shown and discussed.

Keywords: Micro Cladding, High Speed, Coating, Surface Functionalization, Surface Treatment and Cladding, Additive Manufacturing


Selective Copper Plating on Polymers Induced by Laser Activated Fillers
Karolis Ratautas, Mindaugas Gedvilas, Ina Stankeviciene, Aldona Jagminiene, Eugenijus Norkus, Nello Li Pira, Stefano Sinopoli, Umberto Emanuele, Gediminas Raciukaitis

Selective plating of metals on polymers has many applications from decorations of artworks to building’s engineering. However, the best prospects of this technology are for electronics application: making conductive tracks for integrated circuits. There are two basic techniques of laser writing for selective plating on plastics: the laser-induced selective activation (LISA) and laser direct structuring (LDS). In the LISA method, pure plastics without any filler can be used. In the LDS method, special fillers are mixed into the polymer matrix. Laser writing for selective plating is fast and cheap for prototyping. Moreover, there is material saving because it works selectively. However, the biggest merit of this technology is the potential to produce moulded interconnect devices, enabling to create electronics in the 3D structure, thus saving space, materials and cost of production. There are some commercial materials available on the market, but mostly they are based on expensive fillers, usually palladium. In this work, both methods of the laser writing for the selective plating of polymers were investigated and compared.
We present the LDS results on polymeric materials with new carbon-based additives, and the laser processing has been studied using picosecond and nanosecond laser pulses.

Keywords: Laser-induced, selective plating, 3D electronics, polymers, molded interconnect devices.


Free-form fabrication of steel parts by multi-layer laser cladding
Sabina Luisa Campanelli, Carmine Signorile, Andrea Angelastro, Giuseppe Casalino, Antonio Domenico Ludovico

Laser Cladding (LC) is actually one of the most attractive techniques in the group of Material Accretion Manufacturing (MAM) processes. As a surface coating technique, laser cladding has been developed for improving wear, corrosion and fatigue properties of mechanical components. Multilayer laser cladding (MLC) can be used also for high performance part repair and as a rapid manufacturing process. Thus, the application of laser cladding technology is nowadays widely extended in several industrial sectors due to its advantages for high added value parts direct manufacturing and repairing. Multilayer laser cladding (MLC) combines powder metallurgy, solidification metallurgy, laser, CAD/CAM, CNC, rapid prototyping and sensors technologies. This process allows to produce metal components ready to use, in a single step, without the need for molds or tools and using a wide variety of metals, including those very difficult to work with conventional techniques.
The aim of this work was to manufacture MLC steel parts using a CO2 laser with a maximum power of 3kW. The effect of the main process parameters (laser power, travel speed, powder flow rate, degree of overlapping) on the properties of built parts was investigated. A Taguchi experimental plane was used to reduce the number of experiments and a mathematical model was applied in order to obtain an optimized degree of overlapping between adjacent layers and between tracks. Performance of the MLC samples were analyzed in terms of density, macro structure, adhesion to the substrate and microhardness. The powder material chosen for experiments had a composition close to a maraging steel (grade 300). Experimental results showed that high density parts could be produced with a limited number of tests.

Keywords: multi-layer laser cladding, process parameters, optimization, free-form fabrication


Industrial Laser Technologies for Shipbuilding
Aleksandr N. Aleshkin, Valeriy M. Levshakov, Natalia A. Steshenkova, Gleb A. Turichin, Nikolay A. Nosyrev

Laser welding technologies are widely applied for welding of thin-wall constructions. The shipbuilding industry requires high-performance production technologies for the heavy gauges. A hybrid laser-arc welding technology which provides higher productivity, improvement of production effectiveness and reliable quality of welded joints is the most promising technology for this task. JSC Shipbuilding & Shiprepair Technology Center (JSC SSTC) jointly with Saint-Petersburg Polytechnic University performed a complex of studies, including modeling and full-scale experiments, for the purpose of development of industrial hybrid laser-arc welding technologies. The dynamic model of the deep penetration hybrid laser-arc welding process, based on variational principle, was designed. This model specifies the dynamic processes (including self-oscillating) effect on the welding seam formation. Designed model takes into account melt flow, waves traveling on the
melted pool surface, viscosity of the melted metal, capillary tension, return pressure and laser radiation parameters. Experimental researches were carried out on the preproduction models of technological complexes developed by JSC SSTC and equipped with 16 kW and 25 kW fiber lasers.
At the present time JSC SSTC is developing the technology for vertical position hybrid welding for high-strength steel over 40 mm thickness. Industrial hybrid laser-arc welding technology for butt-welded and T-joints up to 20 mm thickness was approved by Russian Maritime Register of Shipping (RMRS).

Keywords: hybrid laser-arc welding; vertical position welding; shipbuilding steels


Laser direct metal deposition for alloy development: use of nominal composition alloy powder as compared to mixed powder feeding with matched composition
Maria Jose Tobar, Jose Manuel Amado, Eva Díaz, Javier Montero, Armando Yáñez

In this work we test the feasibility of using the Laser Metal Deposition Process in the field of alloy development. Two powder blends are included in the powder feeding system, in independent hoppers, and mixed on -fly with weight mixing ratios as set by the user. Two mixtures were tested, Tribaloy 800+Ni and Tribaloy800+Ni20Cr, in proportions equivalent to the Tribaloy 900 composition. The microstructre of the mixed deposited material was compared with that of the nominal blend. Promising results were obtained with the first mixture (T800+Ni), while the second one (T800+Ni20Cr) rised questions to be considered about the entalphy of formation of the respective alloys and the relevance of using similar powder sized.

Keywords: Tribaloy, Laser Metal Deposition, Co-Ni Alloy.


Effect of Sensitization on Pitting Corrosion Resistance of Laser Melting 304 Stainless Steel
Mohammed Jasim Kadhim Al-Tameemi, sami Ibrahim Al-rubaiey, Zaman abdualrazaq abdualwahab

The present paper presents an attempt to improve the corrosion resistance of sensitized 304 stainless steel by pulsed laser surface melting. Tafel extrapolation technique was used to determine the corrosion rates in 3.5% NaCl in four conditions. These conditions are as-received, sensitized, laser treatment for as received stainless steel and laser treatments after sensitization. The results obtained are expressed in terms of corrosion parameters through electrochemical behavior namely, Eo, Io, ECorr., EP, IP, EPit. And IPit. Detailed analysis found that these parameters are strongly dependent on the microstructures of the stainless steel. The results reveal when the potentials increase means the microstructure becomes thermodynamically more stable and has good corrosion resistance. The above electrochemical parameters for sensitized 304 stainless steel show that the localized corrosion rate increases which affected the phases. The laser surface melting treatment shifts the potential toward noble direction. The corrosion current densities values shift to lower values. The comparison of anodic polarization curves indicates that the corrosion rates for laser treated samples are reduced. Increasing the corrosion resistance means that the most inclusions at the surface have been dissolved in the structure due to melting. An interesting feature is the systematic shift of the pitting potential in the noble region with a laser melting. This results confirms that the laser treatment can be used successfully to improve the localized corrosion resistance.


Influence of particle size on heat affected zone in laser cladding
Daichi Tanigawa, Nobuyuki Abe, Masahiro Tsukamoto, Yoshihiko Hayashi, Hiroyuki Yamazaki, Yoshihiro Tatsumi, Mikio Yoneyama

Laser cladding is one of the useful surface coating methods for improving the quality of wear and corrosion resistance of material surfaces. Compared with other conventional surface coating methods, such as plasma thermal spray and transferred arc welding, laser cladding can produce much better coatings with minimum dilution and well bond to the substrate. When cladding layer is produced, heat affected zone (HAZ) is formed in the substrate. In order to reduce the area of HAZ, heat input needs to be reduced. In this study, influence of particle size on HAZ was investigated. The cladding layers were produced at various heat input and particle size. Ni-Cr-Si-B alloy powder with the average particle size were 30, 40 and 55 μm were deposited on the C45 carbon steel substrate. The area of HAZ was measured with optical microscope. The results showed that the cladding layers with well attached to the substrate were produced at smaller heat input by using smaller powder material. The area of HAZ with 30 μm powder was about 30% smaller than that with 55 μm powder


Analysis and optimization of process parameters in Al-SiCp laser cladding
Ainhoa Riquelme Aguado

The process parameters of the laser cladding have great effect on the clad geometry and dilution of the single and multi-pass coatings of an aluminum matrix composite reinforced with SiC particles (Al/SiCp) on ZE41 magnesium alloys using a high-power diode laser (HPLD). The influence of the laser power (500-700 W), scanning speed (3-17 mm/s) and focal position of the laser beam (focus, positive and negative defocus) on the shape factor, the cladding -bead geometry, the cladding-bead microstructure including the presence of pores and cracks, and mechanical properties such as hardness has been evaluated. From the measured values, different contour maps were produced, which show the correlation of these process parameters and their influence on the properties and ultimately, with the feasibility of the cladding process. The importance of the focal position is demonstrated. The different energy distribution of the cross section of the laser beam in focus, positive and negative defocus affects on the cladding-bead properties.

Keywords: Macro Processing, Laser Cladding, focal position, laser parameters.


Strategies for high deposition rate additive manufacturing by Laser Metal Deposition
Antonio Candel Ruiz, Oliver Müllerschön, Simon Abt

To increase the integration of laser based additive manufacturing in the series production major challenges related to the production costs and deposition rates still need to be overcome. Laser Metal Deposition (abbr. LMD), also known as Laser Cladding or Direct Metal Deposition, is regarded as an established technology for repairing components and producing coating systems with defined properties in the petrochemical and heavy duty industry, as well as in medical engineering and aerospace. A novel promising application field for LMD is the use of the process as additive manufacturing technique.

By contrast with the powder bed technology, by means of LMD it is possible not only to generate complete parts but also to deposit defined 3D structures on existing components. In this way, an alternative to additive manufacturing from scratch is given: a combination between conventional processing and advanced laser additive manufacturing can be applied to reduce the production costs. Also geometrical modifications as well as the production of local reinforcements to adapt a basis design to different requirements can be achieved. Nevertheless, with a view to the utilization of the process in the series production, efforts have to be made to increase the cost effectiveness of the process. The present work focuses on the possibilities of LMD as additive manufacturing technology, novel strategies for the improvement of deposition rates and process efficiency being presented.