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 readingOne Minute Mentor: Effects of Nitrocarburizing on Stainless Steel
September 29, 2017 Source:
Electrochemical measurements show that transpassivity (which is necessary for the onset of pitting) of expanded austenite occurs at appreciably higher applied voltages than for austenite with the same metallic composition but without nitrogen. A potential disadvantage of the presence of pitting-resistant expanded austenite at the surface of a stainless steel that is not itself pitting-resistant, is that on the introduction of damage to the expanded austenite zone, accelerated corrosion of the underlying stainless steel may occur.
The graph shows polarization curves for AISI 316 in as-delivered and in the low-temperature nitrocarburized state. Measurement was carried out in an aqueous 3.5% NaCl solution at room temperature. For the nitrocarburized sample repassivation occurs in the transpassive region, an indication that the material is pitting resistant.
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
Electrochemical measurements show that transpassivity (which is necessary for the onset of pitting) of expanded austenite occurs at appreciably higher applied voltages than for austenite with the same metallic composition but without nitrogen.
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: Nitrocarburizing in a Carrier Gas
August 31, 2017 Source:
The graph shows (a) Micrograph of low-temperature nitrocarburized austenitic stainless steel AISI 316 in an atmosphere of (partly) decomposed urea (in situ activation). The sample was heated to 490°C (910 °F) in 45 minutes and thereafter immediately cooled.
(b) Glow discharge optical emission spectroscopy (GDOES) concentration-depth profiles of low-temperature nitrocarburized stainless steel AISI 316 in an atmosphere of (partly) decomposed urea; see microstructure in (a).
Nitrocarburizing in a carrier gas to which (initially solid) urea was added led to a fast growth of the expanded austenite zone. The gaseous decomposition products of urea that develop in the furnace are highly activating, which means that activation and nitrocarburizing are achieved simultaneously. The hardness measured directly at the surface (not in a cross section) is higher than 1300 HV. It is obvious that the expanded austenite zone consists of a nitrogen-rich and a carbon-rich part.
The near-surface zone consists of nitrogen-expanded austenite, and the carbon-expanded austenite is located underneath. The sum of the two interstitial profiles yields a gradual transition from the surface into the substrate in terms of total interstitial content.
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
Nitrocarburizing in a carrier gas to which (initially solid) urea was added led to a fast growth of the expanded austenite zone. The gaseous decomposition products of urea that develop in the furnace are highly activating, which means that activation and nitrocarburizing are achieved simultaneously.
Continue readingOne Minute Mentor: Residual Stress Profiles as Determined by X-Ray Diffraction
August 18, 2017 Source:
For nitrocarburizing or consecutive carburizing and nitriding, the typical stress profile is smoother than for nitriding only. The graph shows residual stress profiles determined with destructive X-ray diffraction methods in carburized/nitrided AISI 316. Carburizing/nitriding: 2 hours at 970°F in an atmosphere consisting of 30% CO-70% hydrogen, followed by nitriding (23 hours at 820°F, at KN = 1.14.
For comparison a profile for a carburized (2.5 hours at 970°F, in 90% CO/10% H2) sample and for a nitrided (22 hours at 830°F, in 100% ammonia) sample are given. Residual stress values were calculated assuming that the same elastic constants apply for expanded austenite and austenite. The presented values are therefore only an indication that very high compressive stresses are present.
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
For nitrocarburizing or consecutive carburizing and nitriding, the typical stress profile is smoother than for nitriding only.
Continue readingOne Minute Mentor: Residual Stress Profiles
August 3, 2017 Source: ASM International
Residual stress profiles of nitrided austenitic AISI 316 are shown in the graph.
Continue readingOne MInute Mentor: X-Ray Diffraction Patterns in AISI 316
July 20, 2017 Source:
The graph shows X-ray diffraction patterns of nitrided (and carburized) stainless steel AISI 316. Carburizing was carried out in 20% CO-80% H2 gas atmosphere at 515°C (788 K) for five hours. X-ray diffraction analysis corroborates that the nitrogen content is significantly higher in the sample nitrided at the highest nitriding potential. The 111 Bragg reflections (peaks) are shifted to lower scattering angles, where the largest shift is observed for the highest nitriding potential.
The peak shift is caused primarily by dissolution of nitrogen, leading to a dilation of the fcc lattice; residual stress and stacking faults also contribute. Peaks originating from the unexpanded austenite are visible in the sample nitrided at KN = 0.293, indicating that the γN zone is not as thick as for the samples nitrided at high potentials.
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 X-ray diffraction patterns of nitrided (and carburized) stainless steel AISI 316.
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: Depth Profiles of Nitrided Stainless Steel AISI 316
June 22, 2017 Source:
The graph shows composition-depth profiles of nitrided stainless steel AISI 316 as determined with glow discharge optical emission spectrometry (GDOES). It shows that, approaching from the austenite "substrate" for all nitriding potentials, a relatively steep increase in nitrogen content is established, after which the nitrogen content increases smoothly toward the surface.
Particularly for the higher nitriding potentials, the gradient in the nitrogen content increases again on approaching the surface. This phenomenon is largely explained by the strong concentration dependence of the diffusion coefficient of nitrogen.
The effect of the nitriding potential is also reflected in the hardness-depth profiles: a smooth decrease near the surface 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 composition-depth profiles of nitrided stainless steel AISI 316 as determined with glow discharge optical emission spectrometry (GDOES).
Continue reading