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Real-time monitoring of laser surface hardening of ferrous alloys.

Description: An infrared process monitor was used to monitor in real-time the infrared emissions during laser surface hardening of gray cast iron and 1045 steel. The signal from the monitor was correlated with the hardness and case depth of the laser-treated tracks. Test data show that a linear relationship exists between the monitor output DC level voltage and hardness up to the maximum hardness possible and also between the monitor output DC level voltage and case depth. This simple relationship of the monitor voltage signal with hardness and case depth makes it easy to monitor process hardness, case depth and quality. A calibration test on prototypic material can be used to determine at what voltage level melting occurs and the heat treating process hardness and case depth can be monitored easily by setting an upper and lower bound for the voltage signal. The monitor is also capable of tracking changes in surface quality or flatness of the part that is being treated.
Date: September 30, 1999
Creator: Xu, Z.; Leong, K. H. & Reed, C. B.
Partner: UNT Libraries Government Documents Department

Excimer laser processing of tool steel: Tribological effects of multiple pulse processing and titanium alloying

Description: Excimer lasers were used to modify the surface of AISI type A-7 tool steel, a high C, high V, high Cr material used in many cutting applications. Multiple pulses of laser radiation at 248 nm were used to alter the composition of the surface alloy. Hardness and modulus were not significantly affected by the treatment, but friction in dry sliding against an alumina pin was reduced. The reduction was small but persistent for multiply melted and resolidified surfaces. These surfaces showed a marked increase in the surface Cr concentration. Greater reductions in friction were obtained from a Ti rich surface layer formed by laser mixing an evaporated Ti layer into the material. The friction coefficient of the Ti alloyed surface deteriorated after approximately 1000 cycles, indicating wear=through of the modified surface. The observed properties will be discussed in terms of the excimer laser modification process and the microstructure and composition of the resulting surfaces.
Date: December 1, 1995
Creator: Jervis, T.R.; Nastasi, M.; Griffin, A.J. Jr.; Zocco, T.G.; Taylor, T.N. & Foltyn, S.R.
Partner: UNT Libraries Government Documents Department

Examination of Compatibility of Potentially Cavitation-Resistant Modifications of Type 316LN Stainless Steel with Mercury in a Thermal Convection Loop

Description: A 316L stainless steel thermal convection loop (TCL) containing a variety of stainless steel coupons circulated mercury for 2000 h. The TCL conditions included a maximum temperature of 307 C, a maximum temperature gradient of 90 C, and a Hg velocity of about 1.4 m/min. In addition to mill-annealed/surface-ground 316LN coupons serving as the baseline material, other coupons included 316LN that was 50% cold-worked, 316LN that was given a proprietary surface hardening treatment termed ''kolsterizing,'' and Nitronic 60. The purpose of this test was to examine Hg compatibility with these modest variations of annealed 31 6LN stainless steel that are considered potential improvements over annealed 31 6LN for cavitation-erosion resistance in the Spallation Neutron Source (SNS) target containment system. The results indicated negligible weight change for each coupon type, no significant indication of attack or surface roughening, and generally no interaction with Hg.
Date: August 29, 2002
Creator: Pawel, SJ
Partner: UNT Libraries Government Documents Department

Modeling of Ion Beam Surface Treatment

Description: Use of intense pulsed ion beams is providing a new capability for surface engineering based on rapid thermal processing of the top few microns of metal, ceramic, and glass surfaces. The Ion Beam Surface Treatment (IBEST) process is shown to produce enhancements in the hardness, corrosion, wear, and fatigue properties of surfaces by rapid melt and resolidification. We have created a new coe IBMOD that enables modeling of intense ion beam deposition and the resulting rapid thermal cycling of surfaces. This code has been used to model the effect of treatment of Al, Fe, and Ti using different ion species and pulse durations.
Date: June 1, 1996
Creator: Stinnett, R.W.; Maenchen, J.E.; Renk, T.J.; Struve, K.W. & Campbell, M.M.
Partner: UNT Libraries Government Documents Department

Surface Hardening by Nanoparticle Precipitation in Ni(Al,O)

Description: Ion implantation of O and Al were used to form nanometer-size precipitates of NiO or Al{sub 2}O{sub 3} in the near-surface of Ni. The yield strengths of the treated layers were determined by nanoindentation testing in conjunction with finite-element modeling. The strengths range up to {approximately}5 GPa, substantially above values for hard bearing steels. These results agree quantitatively with predictions of dispersion-hardening theory based on the precipitate microstructures observed by transmission electron microscopy. Such surface hardening by ion implantation may be beneficial for Ni components in micro-electromechanical systems.
Date: April 1, 2001
Partner: UNT Libraries Government Documents Department

Pulsed laser surface hardening of ferrous alloys.

Description: A high power pulsed Nd:YAG laser and special optics were used to produce surface hardening on 1045 steel and gray cast iron by varying the process parameters. Unlike CO{sub 2} lasers, where absorptive coatings are required, the higher absorptivity of ferrous alloys at the Nd:YAG laser wavelength eliminates the necessity of applying a coating before processing. Metallurgical analysis of the treated tracks showed that very fine and hard martensitic microstructure (1045 steel) or inhomogeneous martensite (gray cast iron) were obtained without surface melting, giving maximum hardness of HRC 61 and HRC 40 for 1045 steel and gray cast iron respectively. The corresponding maximum case depths for both alloys at the above hardness are 0.6 mm. Gray cast iron was more difficult to harden without surface melting because of its lower melting temperature and a significantly longer time-at-temperature required to diffuse carbon atoms from the graphite flakes into the austenite matrix during laser heating. The thermal distortion was characterized in term of flatness changes after surface hardening.
Date: September 30, 1999
Creator: Xu, Z.; Reed, C. B.; Leong, K. H. & Hunter, B. V.
Partner: UNT Libraries Government Documents Department

Inside Sandia

Description: Articles in this issue include ``Molten salt corrosion testing,`` ``Pulsed ion beams for thermal surface treatment: Improved corrosion, wear, and hardness properties at low cost,`` ``Unmasking hidden armaments: Superconducting gravity sensor could find underground weapons, bunkers,`` ``Charbroiled burgers, heterocyclic amines, and cancer: Molecular modeling identifies dangerous mutagens,`` ``Revolutionary airbag offers increased safety options,`` ``EcoSys{sup TM}: an expert system for `Green Design` ``, ``Sandia, salt, and oil: Labs` diagnostics and analysis help maintain vital US oil reserve,`` and ``Automated fixture design speeds development for prototypes and production``.
Date: December 31, 1995
Partner: UNT Libraries Government Documents Department

Friction Stir Processing for Efficient Manufacturing

Description: Friction at contacting surfaces in relative motion is a major source of parasitic energy loss in machine systems and manufacturing processes. Consequently, friction reduction usually translates to efficiency gain and reduction in energy consumption. Furthermore, friction at surfaces eventually leads to wear and failure of the components thereby compromising reliability and durability. In order to reduce friction and wear in tribological components, material surfaces are often hardened by a variety of methods, including conventional heat treatment, laser surface hardening, and thin-film coatings. While these surface treatments are effective when used in conjunction with lubrication to prevent failure, they are all energy intensive and could potentially add significant cost. A new concept for surface hardening of metallic materials and components is Friction Stir Processing (FSP). Compared to the current surface hardening technologies, FSP is more energy efficient has no emission or waste by products and may result in better tribological performance. FSP involves plunging a rotating tool to a predetermined depth (case layer thickness) and translating the FSP tool along the area to be processed. This action of the tool produces heating and severe plastic deformation of the processed area. For steel the temperature is high enough to cause phase transformation, ultimately forming hard martensitic phase. Indeed, FSP has been used for surface modification of several metals and alloys so as to homogenize the microstructure and refine the grain size, both of which led to improved fatigue and corrosion resistance. Based on the effect of FSP on near-surface layer material, it was expected to have beneficial effects on friction and wear performance of metallic materials. However, little or no knowledge existed on the impact of FSP concerning friction and wear performance the subject of the this project and final report. Specifically for steel, which is the most dominant tribological material, FSP ...
Date: January 31, 2012
Creator: Smith, Mr. Christopher B. & Ajayi, Dr. Oyelayo
Partner: UNT Libraries Government Documents Department

Low Temperature Surface Carburization of Stainless Steels

Description: Low-temperature colossal supersaturation (LTCSS) is a novel surface hardening method for carburization of austenitic stainless steels (SS) without the precipitation of carbides. The formation of carbides is kinetically suppressed, enabling extremely high or colossal carbon supersaturation. As a result, surface carbon concentrations in excess of 12 at. % are routinely achieved. This treatment increases the surface hardness by a factor of four to five, improving resistance to wear, corrosion, and fatigue, with significant retained ductility. LTCSS is a diffusional surface hardening process that provides a uniform and conformal hardened gradient surface with no risk of delamination or peeling. The treatment retains the austenitic phase and is completely non-magnetic. In addition, because parts are treated at low temperature, they do not distort or change dimensions. During this treatment, carbon diffusion proceeds into the metal at temperatures that constrain substitutional diffusion or mobility between the metal alloy elements. Though immobilized and unable to assemble to form carbides, chromium and similar alloying elements nonetheless draw enormous amounts of carbon into their interstitial spaces. The carbon in the interstitial spaces of the alloy crystals makes the surface harder than ever achieved before by more conventional heat treating or diffusion process. The carbon solid solution manifests a Vickers hardness often exceeding 1000 HV (equivalent to 70 HRC). This project objective was to extend the LTCSS treatment to other austenitic alloys, and to quantify improvements in fatigue, corrosion, and wear resistance. Highlights from the research include the following: • Extension of the applicability of the LTCSS process to a broad range of austenitic and duplex grades of steels • Demonstration of LTCSS ability for a variety of different component shapes and sizes • Detailed microstructural characterization of LTCSS-treated samples of 316L and other alloys • Thermodynamic modeling to explain the high degree of carbon solubility possible ...
Date: December 7, 2007
Creator: Collins, Sunniva R.; Heuer, Arthur H. & Sikka, Vinod K.
Partner: UNT Libraries Government Documents Department