Applied Process and others to begin doing business as Aalberts surface technologies
April 5, 2022 Source: ASM International
Applied Process and other U.S. based thermal processing, surface treatment businesses will begin doing business as Aalberts surface technologies.
Continue readingOne Minute Mentor: Maps of Wear Resistance
November 27, 2017 Source: ASM International
The images show wear maps for (a) treated and (b) nontreated 316 stainless steel. The T316 stainless steel was treated by low-temperature carburization.
Continue readingHigh-impact research to be revealed at Heat Treat 2017
October 4, 2017 Source:
More than 125 presentations of original, unpublished work will be delivered when the ASM Heat Treating Society convenes for its 29th conference and exhibition in Columbus, Ohio, October 24-26.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.
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.
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.
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.
Continue readingOne Minute Mentor: Hardness Depth Profiles of Stainless Steel after Nitriding and Nitrocarburizing
September 18, 2017 Source:
X-ray diffraction analysis indicates that the hardened case consists of a mixture of expanded austenite and expanded martensite. Dissolving nitrogen into cubic martensite causes a tetragonal expansion leading to nitrogen-expanded martensite. In addition, E-carbonitride is present close to the surface. By comparing the hardness profiles in the graph, it can be concluded that nitrocarburizing generally leads to a thicker case than nitriding, and that a slightly higher maximum hardness is obtained after nitrocarburizing.
Martensitic stainless steels have been successfully nitrided and nitrocarburized. An example is given for molybdenum-stabilized AISI 420-type austenitic stainless steel 7C27Mo2.
The graph shows hardness-depth profiles after nitriding (solid lines) and nitrocarburizing (dash-dot lines) for 16 hours of 100 μm strip 7C27Mo2 (molybdenum-modified AISI 420) at the temperatures indicated. Hardness profiles were fitted assuming a sigmoidal function.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Low-Temperature Surface Hardening of Stainless Steel ⇒ Low-Temperature Nitriding and Nitrocarburizing of Other Stainless Steels
X-ray diffraction analysis indicates that the hardened case consists of a mixture of expanded austenite and expanded martensite.
Continue readingOne Minute Mentor: Nitrogen-Expanded Austenite
July 7, 2017 Source:
The graph shows hardness-depth profiles of nitrided AISI 316. A profile for carburizing is shown for comparison.
Lines obtained by fitting a sigmoidal function are given to guide the eye. The hardness values measured directly at the surface (with the same load) were 1585 HV for KN = 2.49; and 1417 HV for KN= 0.293.
The effect of the nitriding potential is also reflected in the hardness-depth profiles. A smooth decrease near the surface is followed by a sharp drop at a position close to the transition from γN to γ. Nitrogen-expanded austenite is very hard, and the transition from the hardened case to the (soft) core occurs within a few microns.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Low-Temperature Surface Hardening of Stainless Steel ⇒ Gaseous Low-Temperature Surface Hardening of Austenitic Stainless Steel
The graph shows hardness-depth profiles of nitrided AISI 316. A profile for carburizing is shown for comparison.
Continue readingOne Minute Mentor: Physical Metallurgy of Expanded Austenite
April 27, 2017 Source:
The microstructural feature responsible for the favorable technological properties resulting from low-temperature gaseous thermochemical treatment is a supersaturation of nitrogen and/or carbon in austenite. This is called expanded austenite.
An investigation of homogenous nitrogen-expanded austenite with adjusted contents of nitrogen (as controlled by gaseous nitriding) showed that nitrogen-expanded austenite has a face-centered cubic (fcc) Bravais lattice. The study also showed that systematic hkl-dependent peak shifts with respect to the perfect fcc peak positions can be explained from the presence of stacking faults .
This is the ultimate proof that the designation "S-phase" is inappropriate, because no new phase develops, but rather a diffusion zone where the austenite lattice is expanded as a consequence of an interstitial supersaturated solid solution.
The graph shows the lattice parameter of (expanded) austenite as a function of the interstitial content of nitrogen and carbon. The data were obtained with x-ray diffraction on nitrided or carburized thin foils.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Low-Temperature Surface Hardening of Stainless Steel
The microstructural feature responsible for the favorable technological properties resulting from low-temperature gaseous thermochemical treatment is a supersaturation of nitrogen and/or carbon in austenite. This is called expanded austenite.
Continue readingOne Minute Mentor: Low-Temperature Surface Hardening of Stainless Steel
April 18, 2017 Source:
The graph shows a schematic time-temperature-transformation (TTT) diagram of austenite with a high nitrogen or carbon content. In order to prevent the development of chromium nitrides/carbides, a long-time low-temperature treatment could be applied. Alternatively, a high-temperature treatment (above 1050 °C, or 1920 °F) combined with fast cooling can be chosen.
The corrosion-resistant nature of stainless steels is due to the presence of a very stable passive layer, mainly formed by the alloying element chromium and oxygen from the environment. Unfortunately, many stainless steels are susceptible to galling, which often leads to expensive materials solutions in applications where stainless steel would otherwise have been the preferred material choice for its combination of strength and anticorrosion properties.
Surface engineering is common practice for improvement of wear performance. The improvement of hardness and wear properties relies on the development of a surface-adjacent case consisting of either a compound layer and an underlying diffusion layer, as for nitriding/nitrocarburizing; or a martensitic transformation, as for carburizing.
Stainless steel poses two challenges in this respect. First, the native passive layer is impenetrable by nitrogen and carbon atoms. Second, nitrogen and carbon react with chromium to form nitrides/carbides, thus withdrawing chromium from solid solution, with the result that corrosion protection is lost.
A remedy for dissolving nitrogen or carbon into stainless steel without the formation of chromium nitrides or carbides would be choosing a high temperature at which nitrides/carbides are no longer stable; or a low temperature at which the incubation time for nitrides/carbides is longer than the treatment time to achieve a sufficiently thick case.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Low-Temperature Surface Hardening of Stainless Steel
The graph shows a schematic time-temperature-transformation (TTT) diagram of austenite with a high nitrogen or carbon content. In order to prevent the development of chromium nitrides/carbides, a long-time low-temperature treatment could be applied.
Continue readingOne Minute Mentor: Iron-Nickel Precipitation-Hardenable Superalloys
November 7, 2016 Source:
It is important to note that tensile properties are influenced not only by heat treatment, but also by control of structure during thermomechanical processing. The graph shows the effects of temperature and grain size on tensile properties of Incoloy 901 forgings in the solution-treated, stabilized, and aged condition. (AC = air cooled.)
Specifically, the graph shows the effect of solution temperatures from 1750 to 2000°F and grain sizes ranging from ASTM 2 to 12 on tensile properties of Incoloy 901 processed using this method. The high-cycle fatigue strength of Incoloy 901 doubled as a result of the reduction in grain size from ASTM 2 to 12. The low-cycle fatigue also improved greatly with decreasing grain size.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Heat Treating of Precipitation-Hardenable Stainless Steels and Iron-Base Superalloys ⇒ Iron-Nickel Precipitation-Hardenable Superalloys
It is important to note that tensile properties are influenced not only by heat treatment, but also by control of structure during thermomechanical processing.
Continue readingOne Minute Mentor: Hardening Martensitic Stainless Steels
September 30, 2016 Source:
Certain anomalies in these steels that should be considered before specifying a heat-treating procedure are exemplified in the opposing injurious effects of the high and low extremes of austenitizing temperature, depending on the subsequent tempering temperature.
Continue readingOne Minute Mentor: Hardening Ferritic Stainless Steels
July 15, 2016 Source: ASM International
Ferritic stainless steels are quite similar in their mechanical behavior to carbon steel.
Continue reading