Robert J. Hull

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...

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

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

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.

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.

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

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.

Laser cladding of oxidation protection coatings on carbon-carbon composites

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

Carbon-Carbon composite materials – carbon fibers surrounded by a carbon matrix – offer the materials industry a unique mixture of high strength and high temperature performance in a lightweight package. While the aerospace industry has been very interested in carbon-carbon for many years for an assortment of high temperature applications, commercial applications for this material are beginning to gain interest and acceptance. One drawback of the carbon-carbon composite is its susceptibility to oxidation in non-vacuum environments. A number of studies are underway to investigate thin coatings which can be applied to carbon-carbon to reduce or eliminate this oxidation effect.This paper will describe the results of experiments on the laser cladding of a variety of protective coatings onto carbon-carbon substrates as oxidation protection coatings. This work, performed using a 12-kW flat-top CO2 laser and a powder delivery system, will be presented. Laser cladding parameters as well as resulting materials characterization and mechanical property tests will be discussed.Carbon-Carbon composite materials – carbon fibers surrounded by a carbon matrix – offer the materials industry a unique mixture of high strength and high temperature performance in a lightweight package. While the aerospace industry has been very interested in carbon-carbon for many years for an assortment of high temperature applications, commercial applications for this material are beginning to gain interest and acceptance. One drawback of the carbon-carbon composite is its susceptibility to oxidation in non-vacuum environments. A number of studies are underway to investigate thin coatings which can be applied to carbon-carbon to reduce or eliminate this oxidation effect.This paper will describe the results of experiments on the laser cladding of a variety of protective coatings onto carbon-carbon substrates as oxidation protection coatings. This work, performed using a 12-kW flat-top CO2 laser and a powder delivery system, will be presented. Laser cladding parameters as well as resulting materials cha...

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...

Surface hardening of 300M steel for air force and industrial applications

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 Science & Technology’s (NIST) high energy standard calorimeters, serve as secondary standards for in-house calibration of LHMEL’s 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 LHMEL’s 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 opportunity to economically calibrate existing power measurement devices on demand to an NIST-traceable secondary standard. The method described has been applied to calibrate systems up to 100 kW while maintaining measurement accuracies to within ± 6.3%.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 Science & Technology’s (NIST) high energy standard calorimeters, serve as secondary standards for in-house calibration of LHMEL’s 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 LHMEL’s 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 opportun...

Design, construction, and operation of 65 kilowatt carbon dioxide electric discharge coaxial laser device

300M steel is a basic structural material used in Air Force and commercial systems. Exhibiting deep hardenability, this alloy is typically used in aircraft landing gear assemblies as well as crankshafts, connecting rods and gearboxes for automotive, industrial and agricultural applications. Improved wear resistance and overall durability of components produced from 300M steel can be realized when surface hardening is achieved while maintaining high ductility throughout the bulk of the material. This paper describes the processing method developed to use laser energy to increase the surface hardness of 300M steel. A study was conducted by the Laser Hardening Materials Evaluation Laboratory (LHMEL) located at Wright Patterson Air Force Base, Ohio, to produce an understanding ofthe interaction of CO2 laser energy with 300M steel. Optical energy coupling efficiency data was matched with the thermal conductance properties of 300M steel to develop a processing method resulting in surface hardening. Surface hardness measurements of 60 Rc are reported with processed region thickness extending to a depth of 1mm. The yield strength, ultimate tensile strength and elongation of the laser hardened test bars were measured and compared to untreated and traditionally hardened specimens. The laser hardening process is described and comparisons made between standard surface treatment methods.300M steel is a basic structural material used in Air Force and commercial systems. Exhibiting deep hardenability, this alloy is typically used in aircraft landing gear assemblies as well as crankshafts, connecting rods and gearboxes for automotive, industrial and agricultural applications. Improved wear resistance and overall durability of components produced from 300M steel can be realized when surface hardening is achieved while maintaining high ductility throughout the bulk of the material. This paper describes the processing method developed to use laser energy to increase the surface hardness of 300M steel. A study was conducted by the Laser Hardening Materials Evaluation Laboratory (LHMEL) located at Wright Patterson Air Force Base, Ohio, to produce an understanding ofthe interaction of CO2 laser energy with 300M steel. Optical energy coupling efficiency data was matched with the thermal conductance properties of 300M steel to develop a processing method resulting in surface hardening. Surface hard...