Search

A low power AO Q-switched Nd:YAG laser operating at 1064 nm has been used to texture the surface of metallic substrates such as nickel, hastelloy, and aluminum. The substrate surface is uniformly exposed to the laser by using a scan head to raster the focused beam across the substrate surface in a specific pattern. The surface texturing effect is manipulated by appropriate choice of laser power, frequency, scan speed, and focal spot size. Texturing the surface in this manner removes contaminants such as debris, oils, and small scratches and also re-flows the surface layer of the metal. The laser parameters, along with surface melt depth and surface morphology, are being used to provide data for modeling the laser interaction with the metal surface. The discussion of the experimental results and initial modeling calculations will be presented.A low power AO Q-switched Nd:YAG laser operating at 1064 nm has been used to texture the surface of metallic substrates such as nickel, hastelloy, and aluminum. The substrate surface is uniformly exposed to the laser by using a scan head to raster the focused beam across the substrate surface in a specific pattern. The surface texturing effect is manipulated by appropriate choice of laser power, frequency, scan speed, and focal spot size. Texturing the surface in this manner removes contaminants such as debris, oils, and small scratches and also re-flows the surface layer of the metal. The laser parameters, along with surface melt depth and surface morphology, are being used to provide data for modeling the laser interaction with the metal surface. The discussion of the experimental results and initial modeling calculations will be presented.

This paper provides an overview of major application areas of laser material processing in mold fabrication. The first area is mold engraving using a laser marking system to deep engrave alphanumeric characters or logos into a mold or to micromachine features into the mold that cannot be accomplished by conventional CNC machining techniques. Another area is the use of lasers machining techniques to fabricate EDM electrodes (metal or graphite) with excellent detail and quality. We are also introducing a new technique known as pulsed laser deposition (PLD) to apply a thin coating to the mold surface to improve surface wear properties of the tool thereby increasing tool lifetime. This is particularly significant in the case of rapid tools such as Direct AIM and aluminum bridge tooling. This overview will provide a coherent picture of how laser materials processing techniques can provide unique opportunities for mold fabrication.This paper provides an overview of major application areas of laser material processing in mold fabrication. The first area is mold engraving using a laser marking system to deep engrave alphanumeric characters or logos into a mold or to micromachine features into the mold that cannot be accomplished by conventional CNC machining techniques. Another area is the use of lasers machining techniques to fabricate EDM electrodes (metal or graphite) with excellent detail and quality. We are also introducing a new technique known as pulsed laser deposition (PLD) to apply a thin coating to the mold surface to improve surface wear properties of the tool thereby increasing tool lifetime. This is particularly significant in the case of rapid tools such as Direct AIM and aluminum bridge tooling. This overview will provide a coherent picture of how laser materials processing techniques can provide unique opportunities for mold fabrication.

Pulsed laser deposition (PLD) is a technique that was developed nearly 2 decades ago to deposit thin films of material on substrates to improve surface properties such as hardness, wear resistance, and lubricity. The Mound Laser and Photonics Center (MLPC) is applying this technology to a variety of coating applications including coating surfaces of molds made by rapid prototyping processes to improve performance of these tools. We are also using PLD to improve surface properties of other materials from plastics to tool steel.PLD is performed in vacuum and uses a high peak power laser to ablate a target composed of the material that is desired for the coating. After traveling a short distance, the ablated material impinges on the substrate with sufficient kinetic energy to imbed into the surface. This results in growing a thin film (0.5 to 1.0 micrometer) on the surface of the substrate that has improved adhesion properties over other coating techniques. In addition to the improved adhesion, the coatings are fully dense and have optimized crystal structure and morphology. Perhaps the most important attribute of the PLD process is that the coating retains the stoichiometry of the target during the film growth process. Coatings grown in this manner are thin enough to cause virtually no dimensional change to the surface making them ideal for mold coating applications.This presentation will provide a brief overview of the principles behind PLD as well as how the process can be controlled through the appropriate choice of laser wavelength, fluence, and real-time monitoring. Examples of how the technology is being used to deposit coatings such as graphite, diamond like carbon (DLC), Ni-200, gold, silicon carbide, and stainless steel will be discussed. The presentation will conclude with a discussion of commercial applications of the technique being pursued by the MLPC.Pulsed laser deposition (PLD) is a technique that was developed nearly 2 decades ago to deposit thin films of material on substrates to improve surface properties such as hardness, wear resistance, and lubricity. The Mound Laser and Photonics Center (MLPC) is applying this technology to a variety of coating applications including coating surfaces of molds made by rapid prototyping processes to improve performance of these tools. We are also using PLD to improve surface properties of other materials from plastics to tool steel.PLD is performed in vacuum and uses a high peak power laser to ablate a target composed of the material that is desired for the coating. After traveling a short distance, the ablated material impinges on the substrate with sufficient kinetic energy to imbed into the surface. This results in growing a thin film (0.5 to 1.0 micrometer) on the surface of the substrate that has improved adhesion properties over other coating techniques. In addition to the improved adhesion, the coatings ...

In precision cleaning operations, it is essential to remove all traces of organic films and other contaminants, such as particles and fibers, from critical aerospace components. In the past, this was accomplished effectively with powerful solvents such as CFC-113, which can no longer be used because of its adverse effects on the environment. Among many alternative cleaning technologies under investigation, use of lasers to remove contaminants has recently shown promise in several applications, particularly in the area of particle removal from semiconductor surfaces for microcircuit manufacture. We present here, results of some of the first definitive studies of removal of organic films from metal surfaces using pulsed lasers. The substrate metals included aluminum and stainless steel, test coupons of which were contaminated with controlled amounts of organic substances (oils and greases) that might be present from normal use or handling of parts made from these materials. The test coupons were laser cleaned with short pulses having wavelengths selected to span a range of physical removal mechanisms from photo-chemical ablation to pure thermal effects (248, 355, and 1064 nm). Cleaning thresholds were measured using sloped irradiance profiles and post-test SEM observation of the position of the boundary between cleaned and uncleaned zones. These test results were combined with engineering studies of optical fiber beam delivery approaches in the design of a system for precision cleaning of the inside surfaces of metal tubes. Quantitative results of the laser cleaning tests and their implications for optical fiber-based laser cleaning systems are presented.In precision cleaning operations, it is essential to remove all traces of organic films and other contaminants, such as particles and fibers, from critical aerospace components. In the past, this was accomplished effectively with powerful solvents such as CFC-113, which can no longer be used because of its adverse effects on the environment. Among many alternative cleaning technologies under investigation, use of lasers to remove contaminants has recently shown promise in several applications, particularly in the area of particle removal from semiconductor surfaces for microcircuit manufacture. We present here, results of some of the first definitive studies of removal of organic films from metal surfaces using pulsed lasers. The substrate metals included aluminum and stainless steel, test coupons of which were contaminated with controlled amounts of organic substances (oils and greases) that might be present from normal use or handling of parts made from these materials. The test coupons were laser clean...

The self-absorption alpha range for the 5.5-MeV alpha emission in 238PuO2 was determined to be 11.7 ± 0.2 μm by measurement of the effective activity on microspkerical sources of from 150 to 250 μm diameter. A function was derived and experimentally tested which related the fractional escape of the total alpha emission to the range-radius ratio of the microspherical source. An energy distribution function was also derived for the alpha emission from a microspherical source which agreed quite well with the experimentally determined spectrum above 1 MeV. It is suggested that the derwed function provides a more accurate description of the energy region below 1 MeV than the experimental data.