Functional Martensitic Stainless Steel Coatings by Cold Spray
October 9, 2019
Source:
Researchers from Iowa State University, South Dakota School of Mines and Technology, VRC Metal Systems, and the U.S. Army Research Laboratory discussed the feasibility of forming martensitic coatings with tailored strength and ductility by cold-spraying austenitic steel powders.
The technology was evaluated by analytical, numerical, and experimental studies. The fraction of martensite transformed in cold-sprayed 316L austenitic stainless steel varied from 3.4% to 36.0%, depending on the process parameters. The remaining austenite could provide ductility and more strength by transformation-induced plasticity upon subsequent severe loadings.
Volume expansion by martensitic transformation will increase the level of residual compressive stresses in the cold-sprayed coating, which enhances the resistance to stress corrosion cracking.
This study confirms that martensitic coatings with tailored strength, hardness, ductility, and residual stresses can be readily formed by cold spray of austenitic steel powders. Such functional martensitic coatings can be utilized for surface coatings or repairs of structural parts susceptible to wear or cavitation erosion such as hydraulic turbine parts and propellers.
Jonghyun Lee, Cal Wong, Iowa State University;
Morotolaoluwa Alabi,, South Dakota School of Mines and Technology;
Christian Widner, VRC Metal Systems;
Dennis Helfritch, Victor Champagne, U.S. Army Research Laboratory
https://vrcmetalsystems.com
https://asm.confex.com/asm/itsc19/webprogram/start.html
Researchers from Iowa State University, South Dakota School of Mines and Technology, VRC Metal Systems, and the U.S. Army Research Laboratory discussed the feasibility of forming martensitic coatings with tailored strength and ductility by cold-spraying austenitic steel powders.
Continue reading
Structurally Integrated Damage Tolerant Thermal Spray Coatings
Source:
Researchers from Stony Brook University’s Center for Thermal Spray Research reported in this presentation that cermet coatings applied via high-velocity thermal spray are used in aggressive wear situations and are almost always coupled with corrosive environments.
Despite its widespread use, the technology has lacked generalized scientific principles for robust coating design, manufacturing, and performance analysis. However, advances in process and in situ diagnostics have provided significant insights into the process–structure–property–performance correlations, providing a framework-enhanced design.
In this overview, critical aspects of materials, process, parametrics, and performance were discussed through exemplary studies on relevant compositions. The underlying connective theme is understanding and controlling residual stress generation, which not only addresses process dynamics, but also provides linkage for both system (e.g., fatigue) and the surface (wear and corrosion) performance. This presentation provided an overview of structurally integrated coating design and remanufacturing of components.
Sanjay Sampath, Stony Brook University, Center for Thermal Spray Research
https://www.ctsr-sunysb.org/
https://asm.confex.com/asm/itsc19/webprogram/start.html
Researchers from Stony Brook University’s Center for Thermal Spray Research reported in this presentation that cermet coatings applied via high-velocity thermal spray are used in aggressive wear situations and are almost always coupled with corrosive environments.
Continue reading
Air Products develops procedures to optimize furnace atmospheres for annealing
October 7, 2019
Source:
Engineers from Air Products and Chemicals Inc., Allentown, Pa., discuss the proper specification, measurement, and control of annealing furnace atmospheres, which are critical to achieving the required metallurgical and microstructural results, at Heat Treat 2019. With proper process control, annealing plants can reduce or eliminate some common problems, such as sooting, oxidation, sticking, and distortion.
Usually, an atmosphere control system can help heat treaters improve the quality and consistency of their processes. Air Products has been serving this industry for many years and provides the customers with ideal atmosphere solutions and troubleshooting knowledge/capability.
This paper reviews years of field experience with nitrogen and hydrogen-based atmosphere systems, and includes case studies of Air Products’ innovative atmosphere monitoring and control solutions.
Title: “Trouble Shooting and Optimization of Nitrogen-Hydrogen Furnace Atmospheres for Annealing.â€
Authors: Dr. Liang He, Mr. Thomas Philips, Mr. Donald Bowe, Dr. Ranajit Ghos, Mr. Mark K. Weise, Air Products and Chemicals Inc., Allentown, Pa.
https://www.asminternational.org/web/heat-treat-2019
Engineers from Air Products and Chemicals Inc., Allentown, Pa., discuss the proper specification, measurement, and control of annealing furnace atmospheres, which are critical to achieving the required metallurgical and microstructural results, at Heat Treat 2019.
Continue reading
Nitrex Metal studies influence of standard deviations on nitriding, ferritic nitrocarburizing
Source:
Jack Kalucki, Nitrex Metal Inc., Montreal, Quebec, discusses how standard allowed deviations in control parameters affect actual results in controlled nitriding and ferritic nitrocarburizing, in a presentation at Heat Treat 2019. These technologies have become commonly used to improve wear resistance, mechanical properties, and corrosion resistance. The framework for process control is based on standards such as AMS 2759/10 and 2759/12A. In all cases, these standards allow for a tolerance in control parameters.
This work presents the influence of standard allowed deviations in control parameters, for example, nitriding potential and temperature for a given furnace class, on actual results when comparing Iron, carbon steel, 4140, and H13 samples. Comparative results point to interesting variations in white layer thickness.
We also discuss other potential factors such as the shift of actual results due to carbon and alloying elements, and the subsequent alteration of results between expected and actual as demonstrated by shifting boundaries on the Lehrer diagram.
As a conclusion, the study underlines the fact that while tolerances are allowed, precise control in specific furnace classes is necessary to obtain an ideal repetition of results. Additionally, improved control lowers gas usage and gas flows to a strict minimum, with a direct impact on the cost of quality, cost of treatment, and emissions affecting the environment.
Title: “How Does Precise Control Affect the Outcome of Nitriding and Ferritic Nitrocarburizing Cycles?â€
Jack Kalucki, Nitrex Metal Inc., Montreal, Quebec
Tuesday, October 15, 2019: 11:00 AM
251A (TCF Center), Detroit
https://www.asminternational.org/web/heat-treat-2019
Jack Kalucki, Nitrex Metal Inc., Montreal, Quebec, discusses how standard allowed deviations in control parameters affect actual results in controlled nitriding and ferritic nitrocarburizing, in a presentation at Heat Treat 2019.
Continue reading
WPI develops color tint-etching method to quantify percentage of bainite in steel
Source:
Engineers from Worcester Polytechnic Institute (WPI), Worcester, Mass., will present a discussion of methods to determine the amounts of various microstructures in steel during heat treating, at Heat Treat 2019.
Austempering is a hardening process based on the isothermal transformation of austenite to bainite. The transformation percentage of bainite must be quantified to determine the bainite transformation kinetics. During the austempering process, if the austempering holding time is not long enough, the bainitic transformation will be incomplete, and the residual austenite will transform to martensite during cooling to room temperature. The result may be a microstructure containing bainite, martensite, and retained austenite.
In the present work, color tint-etching was used to distinguish phases in austempered AISI 5160 steel samples. After color tint-etching, the microstructural constituents display different colors under the optical microscope with polarized light to estimate the percentage of each microstructural constituent. X-ray Diffraction (XRD) analysis with Rietveld refinement was also conducted to determine the percentage of each microstructural feature. These experimental results are compared with those determined by tint etching.
Both results show that longer austempering holding time increases the bainite percentage, while the martensite percentage decreases. However, the martensite percentage determined by the tint-etching method is much higher than that determined by XRD analysis.
Title: “Methods for the Determination of Bainite, Martensite, and Austenite Fractions in Austempered Steel.â€
Authors: Prof. Mei Yang, Mr. Hooman Sabarou, Mr. Zhida Chen, Dr. Yangyang Fan, Prof. Yu Zhong, Prof. Richard D Sisson, Worcester Polytechnic Institute, Worcester, Massachusetts.
Wednesday, October 16, 2019: 2:40 PM, 251C (TCF Center)
https://www.asminternational.org/web/heat-treat-2019
Engineers from Worcester Polytechnic Institute (WPI), Worcester, Mass., will present a discussion of methods to determine the amounts of various microstructures in steel during heat treating, at Heat Treat 2019.
Continue reading
Gasbarre modular furnaces allow companies to adapt as their products evolve
Source:
Engineers from Gasbarre Thermal Processing Systems, Cranston, R.I., will present a discussion of modular vacuum furnaces that allow companies to adapt as their products evolve, or as their product line expands, at Heat Treat 2019. In today’s manufacturing environment, it is important that companies be agile enough to adapt to a changing landscape.
It may be time to take a closer look at modular vacuum furnaces. Introduced originally in the 1970’s, the modular furnace allows companies to adapt as their products evolve, or as their product line expands. The concept incorporates various modules that can be added or removed over time. The base module consists of a cold-wall vessel with insulation, heating system, pumping system, and control system. Various additional cooling and heating modules can be included, or added or removed as required, to enable annealing, brazing, carbonitriding, carburizing, hardening, quenching, or sintering.
The furnace is suitable for processing a single load, or it can be fitted with a preheat/vacuum module, multiple heating modules, and a cooling module to enable processing multiple loads on a continuous basis to meet increasing demand.
Title “Modular Vacuum Furnaces for an Ever Changing World,†by Patrick Weymer, Gasbarre Thermal Processing Systems, Cranston, Rhode Island.
Tuesday, October 15, 2019: 11:40 AM, 251C (TCF Center)
https://www.asminternational.org/web/heat-treat-2019
Engineers from Gasbarre Thermal Processing Systems, Cranston, R.I., will present a discussion of modular vacuum furnaces that allow companies to adapt as their products evolve, or as their product line expands, at Heat Treat 2019.
Continue reading
One Minute Mentor: Hardening temperatures for 440-N-DUR
Source:
Higher hardening temperatures are required for products machined from small bar sizes that have been annealed various times during thermomechanical processing. Secondary carbides become larger and more stable and are more difficult to dissolve during austenitizing. Either a higher austenitizing temperature or longer soak times at lower temperatures, or both, is required to dissolve adequate carbon in solution to achieve a minimum hardness of 58 HRC.
Figure 19 shows the effect of austenitizing temperature and tempering temperature on the hardness of 440 N-DUR. To achieve maximum corrosion resistance in 440 N-DUR, it should be tempered at lower temperatures, avoiding tempering near the secondary-hardening temperatures. Very rapid quenching (oil or gas) is necessary to avoid grain boundary precipitation of chromium carbides, which also has an adverse effect on corrosion resistance. BG-42 typically is used in high-temperature applications where hot hardness (high-temperature hardness) and corrosion resistance are required.
For more information, click on the link below (subscription required), then scroll down the Chapter Contents column on the left of the page, and click on "Special Purpose Through-Hardening Bearing Steels."
https://dl.asminternational.org/handbooks/book/9/chapter/110017/Heat-Treatment-of-Bearings
Higher hardening temperatures are required for products machined from small bar sizes that have been annealed various times during thermomechanical processing.
Continue reading
Cost-effective thermal barrier coating made of one-micron YSZ powder suspended in water
October 3, 2019
Source:
Engineers from the Fraunhofer Institute for Material and Beam Technology IWS Dresden, Germany, report that they have developed a new ceramic heat shield technology in which a powder of yttrium-stabilized zirconium oxide (YSZ) is added to water to form a suspension. This liquid-powder mixture can be sprayed quickly and cost-effectively onto turbine blades or other aircraft parts. Similar thermal barrier coatings (TBCs) applied to aircraft engine components enable reduced fuel consumption.
With the "YSZ suspension spraying," the IWS researchers have developed an alternative process to use a very fine ceramic powder made of yttrium-stabilized zirconium oxide. The grains in this powder have a diameter of only one micrometer or even smaller.
The engineers mix a suspension with water or alcohol. In this way, the particles can be sprayed. The result is a shielding layer that is about 500 micrometers thick. Since no vacuum is required here, the costs remain rather low. Also, large aircraft components can be coated at relatively high speeds.
A coated aircraft turbine can operate at higher temperatures than an uncoated aggregate. For example, the solution developed by Fraunhofer IWS could raise the operating temperature of a turbine by around 150 Celsius degrees at comparatively low cost. As a result, it increases efficiency, extends its service life, and reduces cooling costs. The bottom line is lower fuel consumption.
The IWS process is also attracting great interest in the semiconductor industry. For instance in chip production, the large microelectronics factories use plasma etching chambers. In these chambers, aggressive fluorine compounds repeatedly destroy the chamber walls. Together with small and medium-sized companies, IWS engineers are working on an IGF project to make ceramics such as tungsten carbide sprayable in a cobalt matrix.
https://www.iws.fraunhofer.de/content/dam/iws/enhttps://www.asminternational.org/documents/press/2019/PM-2019_11_fraunhofer_iws_753_early-morning-science_suspensionsspritzen_en.pdf
Engineers from the Fraunhofer Institute for Material and Beam Technology IWS Dresden, Germany, report that they have developed a new ceramic heat shield technology in which a fine powder of yttrium-stabilized zirconium oxide (YSZ) is added to water to form a suspension.
Continue reading
Bodycote shows that machining can affect corrosion resistance of stainless steel
October 1, 2019
Source:
Engineers from Bodycote, Germany and England, will discuss the influence of machining on the surface hardness and corrosion resistance of austenitic stainless steels at Heat Treat 2019. The main goal of low-temperature surface hardening of austenitic stainless steels is a significant increase in surface hardness, while at the same time maintaining superior corrosion resistance. The treatment temperature has to be low enough to achieve a precipitation-free diffusion zone, yet high enough to allow sufficient diffusion depths needed for technical applications.
The results are often influenced by the machining of parts prior to surface treatment. Best results are usually achieved on solution annealed and electro-polished surfaces, but customer needs for certain manufacturing routes, strength considerations, and overall production costs often do not allow for such additional processes.
This paper gives a basic overview on machinability of austenitic stainless steels and how different machining operations such as turning, cold forming, grinding, and additive manufacturing influence the result of low-temperature surface hardening. Possible machining process optimizations for the different machining operations will be presented in order to increase diffusion depth, surface hardness, reproducibility, and corrosion resistance without altering the hardening process parameters.
Title: “Influence of Machining on Low Temperature Surface Hardening of Stainless Steel.â€
Authors:
Mr. Ulli Oberste-Lehn , Bodycote, Duesseldorf, Germany
Dr. Andreas Karl , Bodycote, Landsberg, Germany
Mr. Chad Beamer , Bodycote, London, Ohio
Wednesday, October 16, 2019: 8:30 AM, 251A (TCF Center), Detroit
https://www.asminternational.org/web/heat-treat-2019
Engineers from Bodycote, Germany and England, will discuss the influence of machining on the surface hardness and corrosion resistance of austenitic stainless steels at Heat Treat 2019.
Continue reading
Solar Atmospheres evaluates how nitrogen affects the Lehrer phase diagram
Source:
Engineers from Solar Atmospheres, Souderton, Pa., will present a discussion at Heat Treat 2019 about the use of nitrogen rather than hydrogen as the diluting gas during ammonia gas nitriding for safety, economic, and environmental reasons. They recently carried out gas nitriding studies that showed different white layer phase ratios on pure iron powders than the Lehrer diagram indicates. The widely published Lehrer phase diagram for ammonia/hydrogen gas nitriding of pure iron has been used as a reference guide for selecting ammonia/nitrogen mixtures for nitriding of alloy steels, though the diagram is not precise or accurate when the diluting gas is not hydrogen.
Recent R&D gas nitriding studies on pure iron powders indicate that the use of nitrogen as the diluting gas produces considerably different compound layer (white layer) phase ratios compared to the standard Lehrer ammonia/hydrogen mixtures, according to XRD analysis. Current data reveals that nitrogen shifts the Lehrer diagram phase boundaries to the left. This is pertinent to the topic, as only the gamma prime phase (Fe4N) is desired, not epsilon (Fe2-3N). Literature indicates that Fe4N has uniquely sought-after magnetic properties in some specialized industries. Testing currently is being performed to compare the pure iron results to that obtained when nitriding common low-alloy, medium-carbon steel.
Presentation title: “The Influence of Nitrogen versus Hydrogen Diluting Gas on the Compound Layer Phase Formation during Ammonia Gas Nitriding of Iron and Low Alloy Steels.â€
Authors: Dr. Virginia Osterman, Mr. Donald Jordan, Solar Atmospheres, Souderton, Pa.
Tuesday, October 15, 2019: 9:40 AM, 251A (TCF Center), Detroit
https://www.asminternational.org/web/heat-treat-2019
Engineers from Solar Atmospheres, Souderton, Pa., will present a discussion at Heat Treat 2019 about the use of nitrogen rather than hydrogen as the diluting gas during ammonia gas nitriding for safety, economic, and environmental reasons.
Continue reading 