Coating adhesion by thermal spraying method requires sufficient surface roughness on particle scale particles impacting the surface, particularly in the case of plasma spraying with particle melting state. Grit blasting process is mainly used to create the fine asperities required for spread particles to adhere. To further increase adhesion, the use of laser texturing for metallic substrates is benefit and is already well documented in literature. In the case of ceramic substrates such as alumina, grit blasting with corundum particles is no longer effective in creating a roughness of a few micrometers. Laser texturing therefore appears to be a potential candidate for generating adhesion in coatings. In this work, adhesion mechanisms of three different coatings produced by Atmospheric Plasma Spraying (APS) on a textured alumina substrate were investigated. The influence of substrate surface texturing by two different laser methods, a pulsed nanosecond laser and a continuous laser, was studied. YSZ was chosen as a potential Thermal Barrier Coating (TBC) and Al 2 O 3 and Y 2 O 3 were selected as bondcoats to observe the variation of adhesion mechanisms on ceramic substrates. Textured patterns and coating microstructures were observed by numerical and electron microscopy. Different adhesion mechanisms occurred depending on coating material. Either the geometrical parameters of the pattern and the surface roughness developed by a nanosecond laser and a continuous laser respectively, can promote mechanical anchoring and thus, a real adhesion.

In the cold spray additive manufacturing (CSAM) process, layer-by-layer stacking is a good method to achieve coating AM. Different from AM processes such as selective laser cladding, which can quickly realize trajectory planning based on commercial software, the spraying trajectory of the CSAM process cannot be created easily due to the “one-stroke” character. The spray path cannot be intersected and the coating deposition cannot be interrupted during the spraying process. What’s more, the spray gun or the workpiece held by the robot usually needs to be deflected by a certain angle to compensate the coating edges. An accurate and efficient spraying trajectory for a given workpiece is the most basic and important part in CSAM process. This article proposes a novel parametric layered slicing algorithm for STL files and an optimized rapidly exploring random tree (RRT) algorithm, so as to generate spraying trajectory accurately and quickly, especially for a part with multiple features. The simulation results revealed that the algorithms can efficiently generate the corresponding spraying trajectory for CSAM.

Cold spray process was chosen as a good candidate for dimensional restoration and protection of components. Commercially pure aluminum, aluminum-alloy or titanium were recommended for different applications. This paper investigates laser surface texturing association to enhance durability of sprayed coatings. Laser is easy automated, localized and reliable process. It was applied for prior-surface treatment. Textured surfaces were produced and compared to conventional treatments, such as grit-blasting, in terms of deposition efficiency and adhesion bond strength. Patterns promoted direct particle embedment. Particle-substrate interface exhibited significant temperature rate and strain in cavities. Intimate contacts and particle compressive states were assumed responsible for improvement. The particle deformation and bonding behaviors were evaluated and discussed for the different configurations. Thus, window of deposition was increased with laser surface texturing. Anchoring mechanisms increased two fold the adhesion strength compared to conventional pre-treatments. In one case, the interface was stronger than the coating cohesive strength.

Polymer metallization using cold spray method, due to low process temperature, is a potential candidate to form electrically conducting polymers as well as composites and improve the mechanical properties of their surface (abrasion, corrosion, etc.). Low Pressure Cold Sprayed copper coatings on PEEK (Poly-Ether-Ether-Ketone) based composites reinforced by carbon fibers have been investigated. Cold Spraying involves high erosion on composite materials due to solid state and high velocity particles thus a new way has been developed. Based on the elastic behaviors of organic materials, pure PEEK matrix has been added on the composite surface to behave as an interfacial layer between the composite and the coating. Optimization of the LPCS parameters has then been carried out using a careful choice of powder size distribution in order to avoid substrate destruction, erosion and delamination of the coating. Consequently, dense thick copper coatings have been obtained and analyzed in terms of microstructure implementing SEM observations. Finally, electric measurements have been performed in order to check the efficient metallization of the composites. A new way for metallic coating on organic composites using Low Pressure Cold Spraying is then demonstrated.

Thermal barrier coatings (TBC‘s) being produced at present either by atmospheric plasma spraying (APS) or electron beam physical vapor deposition (EB PVD) are widely used in the hot-temperature sections of turbines to provide thermal and corrosion protections. An emerging technology of suspension plasma spraying has become interesting for the manufacturing of thermal barrier coatings thanks to the useful microstructure including columns similarly to the EB-PVD deposits associated with considerably lower price of production. A narrow window of optimal suspension plasma spraying (SPS) parameters remain an outstanding problem in creating the favorable microstructure. The recent studies demonstrated that the substrate roughness may play an important role in reaching columnar growth of the coatings. This study presents a follow up by showing how the substrate topography obtained by laser surface texturing may be controlled to create regular columnar structure thanks to. The laser generated peaks disposed regularly on the surface can promote columnar structure growth. The formulated suspensions were sprayed onto superalloy substrates coated with powder plasma sprayed bond coats. Optimized previously, plasma spray parameters were selected to generate columnar structures and to find out the influence of the suspension behavior on coating microstructures. The results indicate that columnar SPS coating microstructure can be controlled by optimizing the laser treatment parameters. The control of surface topography may be an important factor to improve the performances of TBC-SPS coatings.

Cold spraying consists in depositing a variety of metals as dense coatings onto metal surfaces. Indeed, copper, stainless steel, nickel, chromium, aluminum, cobalt, titanium, niobium and other metals can all be deposited, as well as metal alloys according to these base-metals and braze powders. The particle-substrate contact time, contact temperature and contact area upon impact are parameters influencing physico-chemical and mechanical bonds. The resultant bonding arose from plastic deformation and temperature at the interface which illustrates why metal coating cannot be sprayed onto rough ceramic substrates. Laser surface texturing has been used as prior treatment to create specific topography. Metal-ceramic has demonstrated a non-deformation of the substrate minimizing intimate bonds. Particle compressive states indicate anchoring mechanisms for laser textured surfaces. Consequently, cold spraying parameters depend on the target material and a methodology can be established with particle parameters (diameters, velocities, temperatures) and particle/substrate properties to adapt the surface topography. Mechanical adhesion is a key issue in cold spray process. As a result, laser surface texturing is a promising tool to adapt the surface to improve adhesion. Metallization process can be achieved.

Cold Spray is a material deposition process where the effects of substrate roughness on cratering phenomenon are often observed. In order to understand and explain crater formation on cold sprayed coatings, the laser surface texturing technique is used. This innovative process allows to control the substrate surface roughness and to create a controlled topography. In this study, five hole sizes from 20 to 100 μm diameters with an angle of 45° were drilled to obtain different working craters. Subsequent, build up of the coating was investigated. Aluminum powder and nitrogen were used for this study. The main gas temperature and pressure were respectively 500°C and 3MPa. The morphology and the microstructure of aluminum coatings were characterized by optical microscopy and scanning electron microscopy. Surface improperly filled crater affects bond strength. The objective is to determine the effect of surface morphology on craterisation weakening the bond strength. The erosion velocity creates locally a hydrodynamic penetration leading to strong erosion.

This study evaluates the effect of laser texturing on the bonding strength of cylinder bore coatings deposited by plasma transferred wire arc (PTWA) spraying. Experiments were carried out on an AlSi 9 Cu 3 engine block sectioned along a plane through the length of the bores. Cylinder surfaces were laser textured on one side and degreased and grit blasted on the other. Laser power, beam angle, and pulse count were varied to determine their effect on hole morphology and coating adhesion. After surface treatment, the engine block sections were rejoined and the cylinder bores were PTWA sprayed with high carbon steel. Coating samples were examined by SEM and cross-sectional analysis and adhesion tests were conducted. The bonding strength of the coatings on the laser textured portion of the cylinder bore was significantly higher than that of the coatings on grit-blasted surfaces and is shown to vary with laser power, beam angle, and total pulses or impacts per hole.

In this work, numerical modeling is used to simulate the effects of laser remelting as a post treatment and as an in-situ component of a hybrid plasma spraying process. Initially, a single-pass 2D model is used to simulate the laser post-treatment process in order to obtain relationships between melting pool depth, relative scanning velocity, and laser power. A 3D finite-element model is then used to study temperature variations during multi-layer deposition of a NiCr alloy by plasma spraying with in-situ laser melting. The effects of phase change are taken into account by defining the enthalpy of the material as a function of temperature. Predicted melting pool depth corresponded well with experimental values.

In the present work, a mechanical alloying (ball milling) method was developed to synthesize NiCrBSi-WC composite powders for HVOF spraying. Coating properties and microstructure are shown to vary with composition and initial powder size prior to ball-milling. With nanometric particles, metallic and carbide powders appear to be intimately linked with WC, forming a highly protective layer. Conversely, with micrometric powders, ball-milled particles appear more fractured and regularly dispersed inside the matrix.

This study analyzes the mechanical properties of aluminum alloy substrates, in particular, changes in flexural behavior of laser-textured surfaces. Bending tests are conducted on samples treated by laser texturing and by conventional methods such as chemical degreasing and sandblasting. A comparison of flexural strengths caused by the different surface pre-treatments method is presented.

To answer current issues adequately considering technical, economic, as well as environmental requirements, material transformation and especially surface treatment industries must be source of innovations to be proactive. As a result, developing new alternative solutions to existing ones had become a top priority. Considering surface treatment processes, conventional ones (thermal spraying, plasma transferred arc) do not allow to consider this approach since the processes themselves (co-treatment of different powders) do not permit to guarantee the initial composition nor do they ensure a sufficient homogeneity to the coating structure. If indeed the dry surface treatment processes have already shown large potential, several limits remain such as an inefficient adhesion, an environmental impact over the life cycle or almost no materials on the market. To overcome these issues hybrid coating technologies (combining several processes) are likely to be developed. From all of them, laser technology seems to be very promising due to its high flexibility considering all the potential parameters (varying power, continuous or pulsed beam, etc.) and the localised treated area. For instance, combining simultaneously a laser with a thermal spray process enables the elaboration of a thick coating showing a good adherence. The ablation laser applied on the substrate surface just before the impacting particles as promoted in the PROTAL process permit to insure a suitable surface state favourable to the particles adhesion. The control of the coating microstructure was not so much studied. That is why, to complete the knowledge in this area, this work aims at studying the influence of laser technology in association with plasma spraying on the coating microstructure and more precisely on the coating mechanical properties. Coatings were characterized by SEM and void content was evaluated through image analysis and Archimedean porosimetry. Mechanical properties were assessed by the four points bending test for evaluating the coating apparent Young modulus.

Surface state plays an important role in particle bonding and formation of the first layer of coatings in thermal spraying. From a chemical aspect as well as a mechanical point of view, in all cases, the substrate surface needs to be optimized to promote the adhesion of the sprayed particles and then the coating. In order to control such parameters, several works have been conducted to avoid drawbacks on sensitive materials. This study aims at developing a laser surface texturation before the spraying process to improve the coating adherence. According to the laser parameters, different surface morphologies (hole diameters, surface roughness, hole depth, etc.) can be developed. The surface material morphologies were characterised by SEM and bond strength was evaluated through ASTM C633 pull tests. This approach has been applied on the system Al 2017 / NiAl and demonstrates a high influence of the laser treatment. However, the thermal effect induced during the laser-matter interaction has to be controlled to avoid negative effects of the substrate properties particularly tribological properties. In this case, a study of the effect of the conventional processes and texturing process on the fatigue properties of substrate were studied.

The field of materials processing experiences many applications and developments in multiple industrial sectors where the used materials have to operate in most cases under extreme conditions (of temperature, pressure, reactivity of the environment, etc.). Under such conditions, he implementation of a system dedicated to the knowledge capitalization and ability concerning the use of technologies of the manufacturing processes remains today very important for the promotion of collective progresses in these fields. This is the main objective of this project which aims at promoting distance learning (e-learning) and at developing new knowledge-based systems to undergo scientific and technological skills. Currently, the research and education world is experiencing many urges of change, partly enabled and stimulated by the new possibilities offered by the Web. There is clear evidence that e-learning offers increased opportunities for training assessment leading to real benefits in terms of learner retention and achievement. This paper outlines the steps of the development of thermal spraying training supports using appropriate technologies in the thermal spraying field.

The aim of this paper is to propose a LCA comparison of different surface preparation processes (degreasing + sandblasting, laser ablation and laser texturing) which tend to be used before thermal spray. The SimaPro software was used and the needs of materials, the energy and the corresponding emissions of each process, were converted to impact scores on human health, ecosystems, and resource conservation (fossil and mineral resources) by mean of the Eco-Indicator-99 method. Laser pretreatments processes present a very good environmental behaviour in comparison with degreasing + sandblasting.

This study reports on the effect of combined pulsed laser ablation and laser pre-heating surface pre-treatments to cold spraying Ti and Ti-6Al-4V on coatings’ microstructure, bond strength and cohesive strength. The Ti and Ti-6Al- 4V coatings were sprayed on pure titanium and Ti-6Al-4V substrates, respectively. Coatings were characterized by SEM and porosity level was evaluated through image analysis. Bond strength was evaluated by standard ASTM C633 pull tests and by the laser shock (LASAT) technique. Cohesive strength was evaluated by the cross-section scratch test method. Results show that among the spray conditions used in this study, laser pre-treatment yielded high bond strength (such that all cases had higher cohesive strength than the epoxy glue). The LASAT technique provided a means to evaluate the influence of the laser ablation energy density and the laser pre-heating temperature. For both Ti and Ti-6Al-4V coatings, surface pre-heating increased the coating bond strength to the substrate. The laser ablation process would either increase or decrease the bond strength of the coating to the substrate depending on the laser energy density. The laser energy density needs to be adjusted as a function of the surface pre-heating temperature in order to optimize bond strength improvement. Coating cohesion did not improve with continuous laser pre-treatment in-between passes. However, the laser pre-heating helped reduce the coating porosity.

In this work, a LCA based on Eco-indicator 99 methodology was used to compare the environmental impacts and benefits of thermal spraying (including APS, HVOF, Flame and Cold Spray) carried out with materials which could be used in application to resist against wear and/or corrosion. The comparison was carried out using the SimaPro 7.2 software, and it was focused on all stages necessary to build the coating, i.e. extraction of raw materials, production of powder, transport, surface preparation, thermal spray operating, until the end of life, as well as emissions (solid, liquid and gaseous) at each stage of a process. As a major result, it appears that the lifetime of the coatings plays a high role. If a coating needs to be regularly replaced or if failure of the coating decreases the lifetime of the component, this almost impact on the LCA. Moreover, there is an influence on the nature of the resources used to build the coating, as well as on the end of life strategies.

This paper deals with coating alternatives to hard chromium plating. Indeed, thermal spraying is already used in industry, but results are not always satisfactory for reasons of porosity and microstructures. In this study, atmospheric plasma spraying (APS) and in situ laser irradiation by diode laser processes were combined to modify the structural characteristics of thick NiCrBSi alloy layers. The microstructure evolution was studied and results show that in situ laser remelting induces the growth of a dendritic structure which strongly decreases the porosity of as-sprayed coatings and increases the adhesion on the substrate. Moreover, no phase transition after laser treatment is observed. At least, a mechanical investigation demonstrates that the combination between the plasma spraying and in situ melting with a diode laser can result in the improvement of mechanical properties. The hybrid process appears to be a possible alternative to hard chromium plating, in order to protect mechanical parts, because of the good mechanical behaviour of NiCrBSi layer. Moreover, the increase of the laser incident power causes an increase of the mean contact pressure, along with coatings hardness.

The quality of thermally sprayed coatings depends on a lot of parameters (spraying power, feedstock injection, morphology of the parts, kinetics and environment). But among them, adherence between the coating and the substrate appears as the fundamental point. To favor a good interaction and also a good adherence between the coating and the substrate, it is often necessary to clean and prepare the substrate surface. Conventionally, solvents and sand-blasting are applied to remove the contaminants and increase the surface roughness for a mechanical anchorage. But according to the substrate nature (ceramic) or the substrate morphology, it can be prejudicial to apply a mechanical treatment due to a peeling of the surface or a decrease of the global properties. By this way some other treatments have to be investigated in order to obtain an appropriate preparation. From all of them (water jet, ice blasting, heating treatment, etc.), laser ablation can be an interesting technology to prepare the substrate surface. The aim of this work was to study the modifications induced by 10 ns single or cumulative pulses of a Q-switched Nd:YAG near-infrared laser and its influence on the interface adhesion. The case of an alumina coating sprayed on a Ceramic Matrix Composite (CMC) has been studied. In these conditions, the laser treatment seems favorable from the adherence point of view according to the mechanical effect (induced by a cone-like structure) and the chemical effect

Pressure to identify alternatives to hard chromium electroplating has increased these few last years, related to environmental requirements, because of the use of hexavalent chromium, a highly toxic substance. The plasma spray technique allows the formation of thick coatings which present moderate adhesion to the substrate and show porosity and formation of oxide interlayers, which impairs to obtain full benefits of the coatings properties. In this sense, a treatment can be necessary to improve the properties of these coatings. In this paper, the effect of an in situ laser melting treatment of NiCrBSi coatings, deposited by plasma spraying was investigated. It is demonstrated by a Life Cycle Assessment (LCA) that this process is clean. Moreover, the corrosion resistance of as-sprayed and in situ remelted layers was evaluated by potentiodynamic polarization curves. The corrosion resistance was increased because of the finer structure and higher densities of the coatings, nevertheless, corrosion mechanisms occurring in all cases are different.