The high power diode laser is a new industrial tool. It has several advantages and disadvantages compared to the conventional industrially used CO<sub>2</sub> and Nd:YAG laser. The most promising areas of application of diode laser have been considered to be thin sheet welding and hardening. Quite a few feasibility studies of the use of diode laser have been carried out in Finland. So far there has been some application in which diode laser is the most suitable laser. Typically, the HPDL is integrated to an industrial robot. The welding of stainless steel housing, car door lock and catalytic converters are typical examples of applications in which diode laser has technological as well as economical advantages over the conventional laser and welding techniques. The welding of these products requires good control over the heat input, short through put time and low investment. The weld cross-section of a diode laser weld is, because of conduction limited welding process, more suitable for these applications than the keyhole welding. Hardening of a large gear wheel presents also a good example of an application in which the diode laser makes it possible to economically produce structures that have not earlier been possible. Hardening requires a special form of heat delivery in order to ensure evenly hardened zone and acceptable quality. The application was performed with two high power diode lasers. The case studies of these four applications are presented and discussed in details in this paper.
High power diode laser (HPDL) is the newest laser tool for industrial manufacturing. The most promising areas of application of HPDL are thin sheet welding and hardening. The HPDL has several advantages and disadvantages compared to lasers CO<sub>2</sub> and Nd:YAG lasers currently used for welding. There is quite a few industrial applications in which diode laser is the most suitable laser. A typical industrial installation consists of a HPDL, an industrial robot, work piece manipulation and safety enclosures. The HPDL welding process is at this moment conduction limited and has therefore different parameters than the keyhole welding. In this study the basic HPDL welding parameters and the effect of the parameters on the welding process, weld quality and efficiency are examined. Joint types tested are butt joint and fillet lap joint. The parameters tested are beam intensity, welding speed, spot size, beam impingement angle. The materials tested are common carbon steel and stainless steel. By the experiments carried out it can be seen that all of these parameters have an effect on the weld quality and the absorption of the laser power during welding. The higher the beam intensity is the shorter also the throughput time is. However, in case of fillet joint the maximum welding speed and best visual out look are achieved with totally different set of parameters. Based on these experiments it can, however, be seen that reliable welding parameters can be established for the welding of various industrial products. The beam quality of the diode laser is not optimum for high speed keyhole welding but it is a flexible tool to be used for different joint types.
Cladding of an austenitic stainless steel with the cobalt-based alloy Stellite 6, a trademark of Deloro Co, has been investigated by using both CO<sub>2</sub> and Nd:YAG laser beams. This material is used for hardfacing in a number of industries, notably power generation and heavy engineering. Alloy powder was fed into the laser beam by using argon as a carrier gas. Clads were produced with a range of processing parameters, and sectioned for metallographic examination. Hardness values measured in the clads increased to a maximum with an increase in powder feed rate. This correlated with a decrease in the dendrite arm spacing observed in the micrographs. Abrasive wear testing also indicated that a finer microstructure resulted in improved properties. The Nd:YAG laser beam was found to be more efficient for melting the powder because it is absorbed to a greater extent than the CO<sub>2</sub> laser beam. Cladding procedures were developed for both types of laser, and it is shown that in order to maximize in-service performance, the energy input of the process should be minimized.