Real-time spectrographic analysis of the melt pool during direct laser deposition process

The Direct Laser Deposition (DLD) method is a relatively new technology which has significantly matured in the last few years. Although this technique has been well known from the mid ’80s, process control is still under investigation. The major application of DLD is in the repair or modification of existing parts or the manufacture of completely new 2-D or 3-D parts. This technology is also commonly used for the addition of special surface layers on a base material, e.g. hard surface wear resistance like Tungsten Carbide (W-C) or diamond cladding layers. These special wear resistance layers can be applied on the top of drill bits or used as a ‘guard layer’ for working machines and various automotive parts, e.g. excavator bucket tips. The real-time spectrographic analysis of the melt pool composition is one from the main factors to be improved. So far compositional monitoring in-situ is not in practical use and still requires development. It was noticed that metal vapor phase occurred in DLD and this can give significant information about the composition created in the melt pool. It is also an indication of the range of temperatures involved in the process. The work reported here centres on studies performed with various laser cladding nozzle configurations and investigates the feasibility of applying real-time spectroscopy and fast digital imaging to the DLD process. Also several metal compositions have already been analyzed in-situ. This research was carried out with conventional Nd: YAG, solid state, CW laser system.