Cermets are composite materials consisting of a ceramic reinforcement and a metal matrix. Conventional tungsten carbide cermet parts containing a cobalt matrix phase are mainly produced by powder sintering. Laser Powder Bed Fusion (L-PBF) is an additive manufacturing technology widely applied for direct fabrication of metal functional parts with complex geometry. The present paper deals with the feasibility study of additive manufacturing of cermet parts by L-PBF using WC-17Co powder. The results showed that parametric optimisation of the L-PBF process allowed the production of solid WC-17Co part. Structural analysis revealed the presence of significant porosity (1.41%) and small-scale cracks in the as-built samples. Post-processing, such as HIP (Hot Isostatic Pressure) significantly improved the structure of manufactured parts. The porosity after HIP was very low (0.01%) and phase analysis revealed that the samples after HIP did not contain the fragile W 2 C phase. Abrasive wear tests showed that the wear resistance performance of additively manufactured parts was comparable to a reference produced by powder sintering. High values of hardness (around 1100 HV 30 ) were observed for the as-built and HIP samples. The study successfully demonstrated the possibility of manufacturing wear-resistant cermet parts by L-PBF.

Effective properties of TBCs may be quantified thanks to different measurement techniques. Image-based analysis represents an alternative method for predicting these effective properties. During the last 10 years, 2D modelling was intensively applied to estimate the thermal conductivity from coating cross-sectional images. However, real coatings present a complex 3D architecture so that the use of 2D computations based on cross-sections has to be validated. In the recent decade, 3D imaging approaches were applied for capturing 3D images of thermal spray coatings with relatively high resolution (up to 1 micrometer). Nevertheless, high resolution brings very large computational systems for which finite-element (FE) methods seem to be unsuitable due to high requirements in terms of computer memory (RAM) capacity. In the present study, a three-dimensional finite-difference-based heat transfer model was developed for analyzing the heat transfer mechanisms through a porous structure by saving RAM usage. An artificial 3D coating image, containing 300×300×300 voxels, was generated from microstructural information measured for a real coating cross-sectional image. In particular, this 3D artificial pore network was generated so that calculations performed on its cross-sections present similar results in comparison with those concerning SEM images of real coating cross-sections. Then, the results computed for the 3D image were compared with those obtained from 2D computations performed on cross-sections of the same 3D image, revealing the differences between 2D and 3D image-based analyses. Finally, the results were then compared with those computed by FE packages (OOF2 and ANSYS).

This paper presents some results of investigation of the cold spraying various composites including metal-ceramics, metal-metal with a new nozzle design. The objective of this study was to develop a nozzle with an ejector that allows the injection of powder components in different points of the gas flow that can provide optimal spray parameters for each component. For this purpose the installation was equipped with three feeders and three powder feed ports. The first one was located in a pre-chamber (high pressure powder feeder) and two others were located in the ejector in supersonic part of the nozzle. Varying the powder injection location of any component allowed us to change the spray parameters of the mixture. Some preliminary spray results of different powder mixtures are presented to illustrate possibilities of such approach. It is shown that an addition of ceramic or metal powder to the sprayed metal can significantly change the spray process and coating characteristics

Laser assisted direct metal deposition (or simply DMD) belongs to the family of laser cladding. This is flexible and efficient method for elaboration of diverse coatings including functionally graded, multi-layered, etc. The coatings are characterized by excellent adhesion (metallurgical contact), low porosity and variable thickness up to several millimeters and even centimeters. Actually DMD technology is under intensive development. The most important objective is to increase product quality, process stability and reproducibility along with the simultaneous decrease of risks, failures and defects both on processes and on end-products. The use of the TRUMPF 505 DMD machine with 5 kW CO 2 laser allowed to scale-up the technology to an industrial level. The targeted applications are related to petrol, chemical and plastics industries where wear resistance is improved by deposition of a hard-phase coating; in aeronautics DMD is used for near net shape manufacturing from Inconel alloys.

Plasma sprayed composite coatings were prepared with a mixed powder of AlCuFeB + aluminium. One focus of this study has been the effect of air plasma spraying processing parameters on the characteristics of quasicrystalline composite coating. In this study, Taguchi L9 design of experiments was employed to study the investigated process parameters. Significant effects on the microstructure were observed. For the composite coating (quasicrystal + aluminium) parameters were optimized, considering phase retention and porosity level. Tribological tests were performed with a ball on disk device at room temperature for this composite coating. Results show that quasicrystal phase can be kept in the coating after spraying.

The debugging-time for polycrystalline MEMS structural layers is the aim of this paper. A description of the fatigue phenomenon for elementary structure in the case of microactuators is presented. It is obtained by combining elementary in situ test benches of varying dimensions and cyclic actuation; in the same way, the debugging-time is determined according to the design and the structural material. Test benches have been developed allowing performance of bending fatigue tests of polycrystalline structural layers, describing the fatigue phenomenon and obtaining a constant debugging-time for a same polycrystalline layer, whatever the excitation frequency and the beams length.

This paper describes the development of a diagnostic system that monitors in-flight particle diameters, velocities, and temperatures during thermal spraying. The system is based on a low-cost CCD camera and user-developed software. The camera incorporates a 732 x 282 pixel sensor with high sensitivity in the near IR range where the only radiation is that of the particles. User-developed software modules handle signal processing, image analysis, calibration, and data visualization. In video images, particles appear as light tracks of varying length, width, and intensity, corresponding (respectively) to velocity, diameter, and temperature. A test case in which Cr 2 O 3 powder is sprayed in a plasma jet demonstrates the capabilities of the diagnostic system. Paper includes a German-language abstract.

This work evaluates the capabilities of a digital camera selected for use in a thermal spray diagnostic system. The CCD-based image sensor, a Sony Exview HAD, was tested in an industrial plasma-spraying process and is assessed in terms of the information it provides about the plasma jet, particle-substrate interactions, and coating growth. Zirconium dioxide and aluminum oxide ceramics are examined as typical powder systems. Paper includes a German-language abstract.

This paper compares two approaches for monitoring in-flight particle properties during thermal spraying, one based on an industrial CCD camera, the other on a commercial diagnostic system. The camera and detector of the diagnostic tool were installed on opposite sides of a jet axis at a point where a workpiece would normally be placed for coating. Test results for a wide range of powder mixtures sprayed using different plasma and HVOF guns show good agreement between the two approaches in terms of the absolute values measured and the basic tendencies of variations in spraying parameters. A statistical evaluation of particle size, speed, and temperature is also carried out in order to determine the influence of process parameters on powder jet characteristics. Paper includes a German-language abstract.