WPI develops color tint-etching method to quantify percentage of bainite in steel

October 7, 2019
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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.”

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

Gasbarre modular furnaces allow companies to adapt as their products evolve

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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

One Minute Mentor: Hardening temperatures for 440-N-DUR

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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  

Bodycote shows that machining can affect corrosion resistance of stainless steel

October 1, 2019
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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.”

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

Solar Atmospheres evaluates how nitrogen affects the Lehrer phase diagram

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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.”

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

Ipsen develops heat treating technologies for additively manufactured parts

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Peter Kerbel of Ipsen USA, Cherry Valley, Ill., will discuss heat treating procedures that Ipsen has developed for additively manufactured parts in collaboration with AM component manufacturers, at Heat Treat 2019. As the industry works to optimize mass production, it is necessary to develop safe, reliable, and repeatable additive manufacturing solutions.

The focus on additive manufacturing is at an all-time high, which means innovators need innovative heat treating solutions for additively manufactured components. Collaborative efforts in which furnace manufacturers work with component manufacturers to understand the process, result in the best possible outcomes.

In this presentation, Mr. Kerbel provides information for those interested in 3D printing for additive manufacturing, so that they will consider the critical role heat-treating plays in this rapidly growing industry.

Presentation title: “Balancing the Speed and Technology of Additive Manufacturing with the Mature and Methodical Thermal Processing Industry.”

Author: Mr. Pete Kerbel, Ipsen USA, Cherry Valley, Illinois

Tuesday, October 15, 2019: 2:40 PM

251A (TCF Center), Detroit

https://www.asminternational.org/web/heat-treat-2019

Seco Vacuum multi-chamber vacuum systems reduce carburizing gas consumption

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Don Marteeny, Technical Director at Seco Vacuum Technologies, Meadville, Pa., will present a discussion of multi-chamber vacuum systems developed for high-throughput, highly precise low-pressure carburizing applications at Heat Treat 2019.

Compared with traditional gas carburizing in continuous or batch integral quench atmosphere style furnaces, low-pressure carburizing (LPC) run in modern vacuum furnaces reduces carburizing gas consumption while providing more consistent results when considering case depth, surface hardness, and core hardness. Multi-chamber furnaces provide this level of precision, while also maintaining the high production level required in automotive or aerospace applications.

To understand the potential benefits of these systems, two sample applications will be presented using a triple chamber semi-continuous vacuum carburizing system. Both oil and gas quenching capabilities are considered. The results show the semi-continuous, triple chamber design is capable of similar results, if not superior, while providing increased productivity and uptime versus more traditional multi–furnace or continuous furnace systems.

Title: “Triple Chamber Vacuum Furnace Systems – The Low Pressure Carburizing Workhorse”
 

Speaker: Don Marteeny, Seco Vacuum Technologies Technical Director
 

Thursday, October 17, 2019 at 10:20 am in Room 251C (COBO Center)
 

https://www.asminternational.org/web/heat-treat-2019

One Minute Mentor: Effect of tempering temperature on Type 440C

September 26, 2019
Source:

The graph (Figure 18) shows the effect of tempering temperature on the hardness and retained austenite content of Type 440C stainless steel austenitized at 1065°C (1950°F). To achieve maximum corrosion resistance, 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 have 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. A typical thermal treatment designed for high-temperature applications for BG-42 is:

Austenitize 1115–1130°C (2040–2065°F) 30 min + 30 min/each additional inch of thickness, salt bath or in vacuum under partial pressure of argon;

Quench in oil to room temperature, or in salt to 565°C (1050°F), then AC to room temperature;

Snap temper 150°C (300°F) for one hour;   

Subzero cool to −75°C (−100°F);  

Double temper at 525°C (975°F) for two hours.

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

Excillum Metaljet X-ray tube replaces solid anode with molten metal jet for longer life

September 25, 2019
Source:

Excillum AB, Sweden, has developed the MetalJet x-ray tube, in which a conventional microfocus tube with a solid-metal anode, is replaced by a liquid-metal jet. This type of anode is continuously regenerated and already in the molten stage. Therefore, the classical power limit of an x-ray source, reached when the anode is permanently damaged by the electron beam, may be disregarded. Especially in the microfocus x-ray spot size range, from about 5 µm diameter to a few tens of µm, a source based on a liquid-metal-jet anode significantly outperform a classical solid anode x-ray source.

Excillum has now launched Dynamic Adaptation technology on its MetalJet range of x-ray sources. The technology enables MetalJet market-leading brightness for even longer operational periods. For industrial applications such as metrology, inspection, or nondestructive testing of automotive, aerospace, medical, and semiconductor components, the continuous and reliable operation of the test equipment is key.

Dynamic Adaptation technology continuously adapts the e-beam to the natural aging of the cathode. The development of the technology has been possible based on the experience and expertise that Excillum has gained in the area of advanced e-beam control. Dynamic Adaptation technology can enable more than one-year of 24/7 continuous operation (i.e. >8000 hours) before any cathode exchange is required.

This significant improvement will provide improved performance, reduced downtime, and lower operational cost. Dynamic Adaptation is from now on included in new MetalJet x-ray source shipments, and existing MetalJet sources can be upgraded to include the new technology.

www.excillum.com