Laser cladding is a surface treatment technology in which thick, dense and metallurgically adhered metallic layers are deposited on various structural steels with relatively low heat input, high accuracy and reproducibility. Laser cladding processes used in industrial cladding are largely based on the use of CO 2 or Nd:YAG lasers. High power diode lasers (HPDL) with rectangular beam spots are regarded as ideal laser sources for laser cladding processes, due to their compact size, high electrical to optical efficiency, easy operation, and low investment and running costs. In laser cladding of large surface areas, the affectivity of the laser cladding process becomes more important, i.e. high laser powers, wide laser beam spots, and high coating material feedrates are regarded as beneficial. In order to optimise the cladding process for such applications, special attention has to be put on devices used to deliver the coating power to the process. In the present work, various parameters in effective HPDL cladding are described and new approaches to optimised HPDL cladding process are described. The performance of a new HPDL cladding powder delivery nozzle will be presented and discussed. Abstract only; no full-text paper available.

Thermal sprayed WC-metal binder cermet coating is widely used for their resistance to abrasive wear in various harsh environments and generally sprayed by high velocity oxy-fuel (HVOF) method and atmospheric plasma spray method (APS). However, even during HVOF spraying, WC-metal binder cermet powder has to be exposed to high temperature flame jet for heating and accelerating, furthermore, oxygen is usually entrained into the flame jet, the decomposition and decarburization of tungsten carbide owing to the oxidation of WC, cannot be totally eliminated. This frequently causes defects such as pores, cracks and unmelted particles, which deteriorate coatings properties. To improve the properties of sprayed coatings, numerous studies have been examined post treatments such as laser irradiation, diffusion treatment, hot isostatic pressing (HIP) treatment, sealing treatment. Laser irradiation was speedy treatment and simplicity of process control and enables not only the post treatment but also the pre and simultaneous treatment by combining with spraying process. However, it is not easy to produce a uniformly treated coating by conventional laser treatment method as desired. To obtain a near-uniform beam intensity for practical laser irradiation, a kaleidoscope was installed in a conventional YAG laser. In this work, laser beam properties of YAG laser equipped with a kaleidoscope and its effect on surface modification of WC-25%NiCr coating was investigated. Abstract only; no full-text paper available.

Laser cladding is a novel way to produce metal matrix composites for need of abrasion resistant coatings. There are, however, few comparative studies concerning the choice of reinforcing material and the metallic matrix material. In this study, MMC’s were formed from vanadium-, tungsten- and titanium carbides mixed with tool steel M2, Stellite 21 and NiCrBSi-alloy. The abrasion resistances were tested using rubber wheel abrasion apparatus. The wear surfaces were examined. The best results were achieved by M2 tool steel with vanadium carbides.

Wear resistance of materials in very aggressive environment of different industrial sectors like drilling, mining, cutting, etc, appears to be critical and many efforts have been made to limit the major economic loss that represents a broken or damaged tool. The objective of the CLADIAM project (G5ST-CT-2002-50179) is to develop a cladding technique to coat complex parts based on an innovative cladding material composed of diamond pellets and cast spherical tungsten carbide particles using an automated high power diode laser (HPLD) equipment. The result of these two and a half years of work has led to the finalization of following techniques: A pelletizing alloy that takes into account the constraints of laser cladding, Enrobing of diamond particles to avoid their damage, An industrial technique, technically and economically efficient, of laser cladding that allows the realization of complex shapes. The combination of a new technique of wear and abrasion tests has led to the characterization of the obtained cladding. The results have been compared with the tests on industrial parts in severe and even extreme wear conditions. The development of this new cladding technology has been possible thanks to the use, the characterization and the optimization of specific cladding nozzles associated with the special beam of high power diode laser. The results obtained are very encouraging and open the doors to new claddings that combine the specific advantages of diamond and tungsten carbides for the nature of cladding, but also the fineness of the structure, the improvement of behaviour in wear conditions, the small thermal impact of the parts, some of the well known advantages of laser cladding.