Michael L. Lander

Laser hardening of Austempered Ductile Cast Iron (ADI)

Abstract Austempered ductile cast iron (ADI) has emerged as a major engineering material in recent years. In addition to high strength and relatively light weight (compared to steel), it has high ductility, good wear resistance and good damping capacity. It has many potential applications such as automotive components (e.g. crank shafts and gear boxes) as well as aircraft components (landing gears). In many structural applications, (e.g. aircraft landing gear) it is often required that the material be hardened at the surface while the interior of the material must remain soft or ductile. The higher hardness at the surface layer imparts excellent wear resistance while the soft inner core provides higher toughness and fracture resistance. The conventional methods of surface hardening such as carburizing and nitriding or shot peening have several limitations, e.g. retained austenite, massive carbide formations and insufficient case depth. In recent years, there has been significant interest in use of laser i...

Laser material test results from Russian high-power carbon monoxide laser

Researchers from the United States and Russia conducted laser-material interaction tests at the LOK Company, St. Petersburg, Russia. These tests were conducted using a one-of-a-kind, continuous wave, supersonic, e-beam-sustained carbon monoxide (CO) laser. The purpose of these tests were to characterize the laser while performing collaborative research between scientists from Russia and the United States. Additionally, the testing verified previously- reported laser characteristics. All planned laser-material interaction tests were successfully conducted. Several material samples were irradiated by the CO laser to allow calculation of the laser energy and power levels. Statistical errors were reduced by testing materials with different characteristics at varying laser energy and power levels. Laser-material interaction tests were also conducted at varying distances from the laser output window to assess beam quality and divergence.

Characterization of the thermal performance of high heat flux systems at the Laser Hardened Materials Evaluation Laboratory

When developing a high-heat-flux system, it is important to be able to test the system under relevant thermal conditions and environmental surroundings. Thermal characterization testing is best performed in parallel with analysis and design. This permits test results to impact materials selection and systems design decisions. This paper describes the thermal testing and characterization capabilities of the Laser Hardened Materials Evaluation Laboratory located at Wright-Patterson Air Force Base, Ohio. The facility features high-power carbon dioxide (CO2

Pulsed-laser capabilities at the Laser-Hardened Materials Evaluation Laboratory (LHMEL)

and neodymium:glass laser systems that can be teamed with vacuum chambers, wind tunnels, mechanical loading machines and/or ambient test sites to create application-specific thermal and environmental conditions local to the material sample or system. Representative results from recently conducted test series are summarized. The test series described demonstrate the successful use of a high power CO2 laser paired with environment simulation capability to : 1) simulate the expected in-service heat load on a newly developed heat transfer device to ensure its efficient operation prior to design completion, 2) simulate the heat load expected for a laser diode array cooler, 3) produce thermal conditions needed to test a radiator concept designed for space-based operation, and 4) produce thermal conditions experienced by materials use din solid rocket motor nozzles. Test diagnostics systems used to collect thermal and mechanical response data from the test samples are also described.

Continuous-wave carbon dioxide laser system producing output power up to 135 kW

Pulsed laser capabilities at the Laser Hardened Material Evaluation Laboratory are described relevant to optical coupling, impulse generation and laser propulsion. Capabilities of the Nd:Glass laser are presented as well as supporting test systems.

Laser-Hardened Materials Evaluation Laboratory testing facility

The operational characteristics of a 135 kW continuous wave carbon dioxide laser system are described. A brief description of the fast-flowing electrical discharge coaxial laser system is presented followed by a detailed discussion of the operational and output characteristics of the device. Diagnostics systems configured to measure electrical discharge voltage and current, mass flow, laser cavity pressure, laser output power, output spatial intensity distribution and output temporal stability are described. The data collected with these systems are summarized with subsequent analyses presented and compared with theory. The 135 kW carbon dioxide laser is located at the Laser Hardened Materials Evaluation Laboratory (LHMEL) at Wright-Patterson Air Force Base, Ohio, USA. The device was developed and is currently operated for the purpose of characterizing the thermal response of materials.

Impulse coupling measurements for an ORION demonstration

Supporting laser/materials interactive testing for the past 15 years, the Laser-Hardened Materials Evaluation Laboratory (LHMEL) has efficiently performed low-cost high-volume testing of materials samples placed in various environmental simulation conditions. The capabilities of the upgraded LHMEL facility carbon dioxide laser and related test support systems are described. The LHMEL facility is part of Wright Laboratories Materials Directorate and is located at Wright-Patterson Air Force Base, Ohio. Two lasers producing a 10.6 micron wavelength, continuous wave output and having a flat-top spatial intensity distribution are currently available for testing. The test parameters achievable with the 15 kW LHMEL I and the 100 kW LHMEL II devices are discussed. In addition, various test environmental simulation capabilities are described. Vacuum environments in the 1 X 10-6 torr range are routinely achieved for samples ranging in size from 1 cm to 120 cm. Atmospheric velocities approaching Mach 1 for samples up to 7 cm are provided. Mechanical loads up to 55,000 lbs of force can be incorporated into ambient or high velocity testing schemes. Finally, the capability of the facility data acquisition system is described.

Experiments in laser cutting of thick steel sections using a 100-kW CO2 laser

We discuss results of recent measurements of laser impulse coupling coefficients completed at the LHMEL Nd:glass laser facility at Wright-Patterson AFB. Impulse coupling was measured at 125 ns pulse duration and 1.06 μm wavelength on specially designed heterogeneous targets in vacuum. With these targets, we obtained substantially enhanced impulse at modest laser fluence. One application of this work is to provide a means to execute a demonstration of the ORION concept using repetitively-pulsed, kW-class, diffraction-limited lasers with pulse energy on the order of 100 J.

High power calibration of commercial power meters using an NIST‐traceable secondary standard

Cutting of thinner steels has been an active laser application for many years. As technology advances have enabled available laser output power to increase, the thicknesses of steels that can be cut at competitive feed rates has also increased. This paper will describe a series of laser cutting experiments performed on a 2” thick steel cross-section using a 100-kW CO2 flattop laser. The application driving these experiments was from the salvage industry and the objective was to meet or exceed the cutting rates of the currently used torches but with a cleaner process (i.e. fewer by-products). The paper will discuss the results of these successful experiments including laser parameters used, both with and without oxygen assist, and cutting rates achieved.Cutting of thinner steels has been an active laser application for many years. As technology advances have enabled available laser output power to increase, the thicknesses of steels that can be cut at competitive feed rates has also increased. This paper will describe a series of laser cutting experiments performed on a 2” thick steel cross-section using a 100-kW CO2 flattop laser. The application driving these experiments was from the salvage industry and the objective was to meet or exceed the cutting rates of the currently used torches but with a cleaner process (i.e. fewer by-products). The paper will discuss the results of these successful experiments including laser parameters used, both with and without oxygen assist, and cutting rates achieved.

High power calibration of commercial power meters using an NIST-traceable secondary standard

For the past 19 years, the Laser Hardened Materials Evaluation Laboratory (LHMEL), located at Wright‐Patterson AFB, OH, has maintained a number of calibrated high energy power measurement devices capable of measuring CO2 powers up to 150 kW. These devices, calibrated annually to the National Institute for Standards & Technology (NIST) high energy standard calorimeters, serve as secondary standards for in‐house calibration of LHMELs commercial power heads and calorimeters. Recent discussions with academic and industrial laser users have identified an industry need for traceable calibration sources above the 1 kW level. This paper describes the methods used to calibrate LHMELs commercial power measurement devices using the LHMEL secondary standards and also describes the process by which other laser users can access these same calibration capabilities to confirm the accuracy of their own power heads and calorimeters. The LHMEL calibration capability offers academic and industrial laser users the opportuni...