High-impact research to be revealed at Heat Treat 2017
October 4, 2017
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View the Technical Program!
More than 125 presentations of original, unpublished work will be delivered when the ASM Heat Treating Society convenes for its 29th conference and exhibition in Columbus, Ohio, October 24-26. The information exchanged in these sessions – as researchers and practitioners share their latest discoveries, theories, and advancements – will have a significant impact on design and manufacturing innovation as well as the fortunes of industry.
One example of the cutting-edge work that will be unveiled is an investigation on the effect of heat treating on additively manufactured medical implants. Additive techniques offer unprecedented design flexibility for dental and orthopedic implants, but the intense heating and cooling spikes associated with direct metal laser sintering can leave the microstructure of titanium – a good bio-material but a poor thermal conductor – in a less than optimum state. To quantify the potential for improvement, researchers evaluated several heat treat processes and measured changes in hardness, residual stress, and corrosion. The promising findings will be shared in a Thursday morning session.
Caption: Optical metallography reveals microstructural differences between the build and deposition planes as well as pores near the surface of an as-printed titanium test sample. Structural mismatch is a source of residual stress, while pores can lead to fatigue fracture and corrosion.
Caption: X-ray diffraction results indicate that heat treating as-printed titanium parts (blue trace) reduces the ratio of α to β phase precipitates as seen in the narrowing of α peaks and the development of β peaks (green, orange, and red traces). This seems to correlate with measured improvements in corrosion resistance because micro-galvanic reactions stemming from phase differences cause pitting in α precipitates, a likely pathway for corrosion.
Another significant accomplishment that will be reported is a new method to predict the quenched and tempered hardness of complex steels based on chemistry data. Two researchers, building on prior attempts to calculate hardness as a function of chemistry, have developed a hybrid model that works for mixed microstructure alloys containing less than 0.5wt%Cr. As Cr levels increase, however, other alloying elements such as Mo and V become more influential, compounding the complexity of the problem. The researchers will describe the new method and its limitations on Tuesday morning.
Caption: A corrective variation on an earlier method for calculating tempered hardness in complex steels based on chemistry shows considerable improvement when measured and calculated data plots are compared side by side.
Caption: Hardness profiles for a 95 mm bar of SAE 4142 steel quenched in water and tempered at 1100°F as calculated from chemistry data using a recently developed method.
The results of several cross-sector efforts will also be presented, including a paper submitted by a group examining the role of vanadium in induction hardened shafts. Vanadium microalloying is common in carbon steel shafts because it increases load capacity. Induction hardening offers additional benefits, but the presence of vanadium adds uncertainty to the process. Seeking clarity, researchers have obtained evidence that, under certain conditions, vanadium carbonitride precipitates formed during induction reduce austenite in the case/core region but not the case. Retained austenite, characterized by compositional gradients and undissolved carbides, is believed to limit case depth and hardenability.
Caption: Cross-sectional images of 1045 steel shafts in various induction hardened conditions reveal distinct differences in case, core, and case/core regions that correspond with the presence of vanadium and its effect on microstructure formation.
Caption: A high volume fraction of martensite (M) revealed by SEM imaging is believed to be the result of a large amount of austenite formed with the help of vanadium during induction hardening of 1045 steel.
More than 125 presentations of original, unpublished work will be delivered when the ASM Heat Treating Society convenes for its 29th conference and exhibition in Columbus, Ohio, October 24-26. The information exchanged in these sessions – as researchers and practitioners share their latest discoveries, theories, and advancements – will have a significant impact on design and manufacturing innovation as well as the fortunes of industry.
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Featured Paper from Heat Treat 2017
July 7, 2017
Source:
Mr. Pete Kerbel , Ipsen USA, Cherry Valley, IL
Today's competitive environment often requires one to do more with less – to make equipment last longer and run more efficiently. As such, there are several factors that go into making your equipment run to the best of its ability. With our industry becoming more demanding, there has never been a better time to ask the question: "Where, and in what, do I invest my money with aging equipment?"
This paper offers a close-up look at what is possible when weighing different options for upgrading an aging vacuum furnace, focusing on the many factors that go into choosing the right upgrades and repairs for both your equipment and process requirements.
Specific topics covered include:
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The three factors you should always consider before replacing a hot zone
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What is required for data acquisition?
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The role preventative maintenance plays in extending your equipment's life span
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How much is too much to invest in aging equipment?
View Abstract
Today’s competitive environment often requires one to do more with less – to make equipment last longer and run more efficiently.
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One Minute Mentor: Plasma Nitriding
January 3, 2017
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Plasma nitriding is a surface-hardening process in which glow-discharge technology introduces nascent (atomic) nitrogen into the surface of a metal part for subsequent inward diffusion. The process takes place in a vacuum chamber, with the workpiece as the cathode (negative potential) in a nitrogen/hydrogen atmosphere at pressures between 100 and 1000 Pa (0.015 and 0.15 psi).
A voltage in the range of 500 to 1000 volts is applied between the metal part and the chamber wall, resulting in the formation of a plasma through which positive nitrogen ions are accelerated against the negative-biased part to be treated. This ionic bombardment heats the piece to the treatment temperature, cleans the surface by sputtering, and provides active nitrogen species for the nitriding process.
The diagram shows the schematic of a device used for glow-discharge plasma nitriding. 1 and 2, gas introduction; 3, thermocouple; 4, cathode; 5, pressure sensor, 6 to 8, needle valve; 9, diaphragm valve; 10, solenoid; 11, vacuum pump; 12, sample holder; 13, sample; 14, anode; 15, sealing ring; 16, stainless tube; 17, window and 18, insulator.
Volume 4D, Heat Treating of Irons and Steels ⇒ Nitriding of Stainless Steels ⇒ Thermochemical Nitriding Treatments
Plasma nitriding is a surface-hardening process in which glow-discharge technology introduces nascent (atomic) nitrogen into the surface of a metal part for subsequent inward diffusion
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One Minute Mentor: Quenching of Hot-Work Tool Steels
January 28, 2016
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Hot-work steels range from high to extremely high in hardenability, so it is possible for them to achieve full hardness by cooling in still air. However, this is not recommended, because intense embrittlement occurs after slow cooling from hardening temperature.
Even with those types having the highest hardenability, sections of die blocks may be so large that insufficient hardening results. In such instances, pressurized nitrogen gas (in vacuum furnaces) or an oil quench is required to achieve full hardness. Hot-work steels are never water-quenched. The figure shows the Continuous Cooling Transformation (CCT) diagram for AISI 6F3.
Volume 4D, Heat Treating of Irons and Steels ⇒Tool Steels ⇒ Heat Treating of hot-Work Tool Steels ⇒ Heat Treatment of H Series and Low-Alloy Hot-Work Steels
Hot-work steels range from high to extremely high in hardenability, so it is possible for them to achieve full hardness by cooling in still air. However, this is not recommended, because intense embrittlement occurs after slow cooling from hardening temperature.
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One Minute Mentor: Austenitizing Powder Metallurgy Steels
December 17, 2015
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Steels of groups A and D as well as 8%Cr or High-V-PM steels are usually austenitized in vacuum furnaces or in various types of furnaces using gaseous atmospheres.
Whereas for conventionally produced cold-work tool steels the adjustment of the working hardness is usually done by a combination of different austenitizing and tempering temperatures, PM steels are typically tempered in a small tempering range, from about 550 to 560°C (1020 to 1040°F) with a variation in austenitizing temperature to adjust the hardness level , as shown in the graph.
This different procedure is explained by the toughness results, which increase when austenizing temperature is reduced. Furthermore, because of high content of fine dispersed stable carbides, grain growth at high temperatures does not take place in these steels. Typical austenitizing temperatures therefore range from 1000 to 1180°C (1830 to 2160°F).
Volume 4D, Heat Treating of Irons and Steels -> Tool Steels -> Heat Treating of Cold-Work Tool Steels—Medium-Alloy Air-Hardening, High-Carbon High-Chromium and High-Vanadium-Powder Metallurgy Steels -> Recommended Heat Treating Practices
Steels of groups A and D as well as 8%Cr or High-V-PM steels are usually austenitized in vacuum furnaces or in various types of furnaces using gaseous atmospheres.
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