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Innovative coatings on light alloys


Design rules for advanced IC engines Calculation methodologies for stress distribution of IC engine with coated valve seats; the deformation and stresses specially in the valve seat area under thermal, mechanical and manufacturing process loading conditions were evaluated. A methodology for investigating the structural behaviour of a cladded valve seat was developed. Commercial finite element programmes were used for the investigations. MSC.NASTRAN and ABAQUS were used to study the structural behaviour of a FIAT engine with a conventional seat-ring as well as cladded valve seat under the following loading cases: - Thermal load. - Load due to valve dynamics. - Mechanical load resulting from the gas pressure. - Assembly load including the press-fit load resulting from the presses of inserting the ring in the cylinder head.
Advanced focusing optics for high power laser diodes: A special optics device to be coupled to the High Power Diode Source was designed. The most important disadvantage of the designed focusing optics is its large size. The diameter of the lenses is 140 mm. The total length of the focusing optics is approximately 700 mm. With this large size it is not possible to integrate the focusing optics in a machine tool and it does not make sense to build the optics with those dimensions. For these reasons the result has to be considered NOT EXPLOITABLE. Advanced beam shaping modules for midrange power laser diodes: Special solutions for the beam shaping and for a direct monitoring of the process were designed. The designed modules could allow optimising the beam shape in accordance to the process specification and to insert in the bundle reduced optical fibres to monitor the process on-line.
Laser cladding systems for rollers manufacturing and automotive applications. Three years after the completion of the project 3 systems for automotive applications and 1 system for rollers manufacturing will be applied in industrial environments. These systems include several exploitable results still not available on the market: - Process monitoring devices. - Powder delivery system for coaxial powder nozzles. Powder delivery system for lateral/off-axis nozzles Within this project a powder delivery system was specifically optimised for LC with lateral/off-axis nozzles. An important feature of the feeding device is the integrated on-line feeding rate measurement and control system. The measuring principle is based on the continuous recording of the weight of the powder feeder during the feeding process using a special balance integrated into the feeding device. Therefore, the actual powder mass flow rate can be calculated as weight loss per time unit. The used balance consists of a bending bar with several strain gauge load cells. The electric signal of the balance is processed by a strain gauge amplifier which is via an A/D card connected to a personal computer. The on-line measurements and control are done by a personal computer and special software. The development of this powder delivery system specifically designed for cladding lateral/off-axis nozzles could allow to identify potential alternatives to the use of coaxial nozzles that in some cases cannot be applied for some accessibility problems related to their typical dimensions. This fact could expand the potential market for LCAA.
- Process monitoring system for LCAA process: A monitoring system able to acquire and elaborate in real time the temperature induced by the process; the laser power and the powder feed rate were established and tested. - Special SW for process monitoring (NOT EXPLOITABLE): Special SW were developed and tested in order to identify potential correlation among the acquired signal and the quality of the realised clad bead. The trials showed that the system (based on the acquisition of the temperature on the surface of the melt pool) is not able to show a direct correlation among acquired parameters and defects when the process is carried out into optimised process parameters windows. Operating near to the optimal process parameters, the defects (cracks) appear in accordance with very complex phenomena at the interface existing between the two main melted phases (the Al and the Powder ones). These phenomena can correlate only to the local chemical combination of Al and Powder phases that is not directly pointed out by variations of surface temperatures. Consequently these defects can be avoided with an optimal selection of the feeding materials that must include elements able to limit the formation of fragile phases within the intermixing region. In any case, the monitoring system developed by CRF/LMS, based on the use of pyrometers for reading the induced surface temperatures, is able to put in evidence relevant variations of the main process parameters that could drive the process outside the optimal process windows generating relevant "non-metallurgical" defects. This device was specifically designed for LCAA and consequently could be applied for a preliminary process optimisation also in industrial plants. Acquired knowledge and competencies will allow the partners involved in the development of such devices to promote the diffusion of similar solutions for general laser surfacing applications.
A special coaxial nozzle for powder delivery was designed, built and tested. The development of this coaxial cladding nozzle for multi-kW fibre coupled YAG laser is a great progress because: - Compared to coaxial nozzle for CO2 lasers the energy coupling rate is twice as good; that means same results with 4kW YAG as with 8kW CO2 or, in other words, energy cost savings. The optical fibre allows a cheaper machine concept (standard robot instead of specific laser machine). - Compared to lateral nozzle the powder efficiency is >90% instead of maximum 65% which means consumable cost savings. The coaxial nozzle allows multidirectional cladding (new applications: rapid prototyping, repairing of complex shapes). Moreover, it can be reasonably expected that this type of nozzle can be connected to fibre coupled diode laser in the near future, which means additional cost savings, and will also make the laser cladding technology attractive for SMEs.
The main sub-result achieved results are: - High efficiency laser diode bars (broadened wave guide; special active layer composition for 840nm wavelength 900µm cavity length; emitter size: 120µm; pitch: 400µm; filling factor: 30%; beam divergences: 35° x 9° (FWHM)). - High efficiency laser diode bars on heat-sink (low smile soldering process; >40W CW output power; typ. operating current <50A; slope efficiency: 1.1W/A; efficiency: 45%). - Improved fibre coupled modules with output power up to 20W in a 400µm fibre (maximum output power reached in a 400µm fibre was: 24W (1.6 times better than the target of 15W)). - Design of a 1.2kW source (with 61 fibres coupled modules each delivering 20W) (NOT EXPLOTABLE). - Design of a special focusing device to be coupled with a 61 fibres bundle (NOT EXPLOITABLE). - Midrange power laser diode sources for direct manufacturing with the following specifications: 30WCW / 48A, 600µm, NA=0.22 fibre, wavelength 835 nm, working distance: 60mm, spot diameter: 1mm, red aiming beam, air cooling system; 60WCW / 35A, 400µm, NA=0.22 fibre, wavelength 835 nm, water cooling.