achieving lightweight, wear resistant steels through nitriding: a low cost heat treatment method could improve the wear resistance of austenitic manganese and aluminum steels. - name plate in steel

In recent years, there has been an in-depth study of high manganese and aluminum ogel steel to understand its potential applications in the military and transport industries.
These steel have a special combination of high strength and toughness, with excellent wear resistance.
Add aluminum from 6% to 8 levels.
Compared with quenching and tempering chromium and molybdenum steel, 8wt % reduces density by 10% to 15%, but also reduces strain hardening and wear resistance.
Wear resistance can pass low-
Cost Case of hardening treatment in a nitrogen atmosphere (nitriding)
It produces a hard layer of alumina, AIN.
In the current study, the effect of aluminum and silicon content on the dynamics of the nitridation process was evaluated for aFe-30%Mn-(6-9%)Al-(l-1. 6%)Si-0.
Steel with a temperature range of 1,9%-652 °c2,012F (900-1,100C). (
Note: All of the following percentages are given by weight percentage).
The results show that, depending on the time and temperature, the surface layer of the nitrogen aluminum plate can be produced up to 550 pm thick.
The amount of silicon is from 1. 1% to 1.
6% had no statistical effect on the diffusion of nitrogen within the range of 1,652-temperature2,012F (900-1,100C).
However, the amount of aluminum increased from 6% to 8.
8% reduces the depth of the AIN surface layer, and increases the calculated activation energy of nitrogenin's thermodynamic diffusion from 64 kilojoules/moles to 79 kilojoules/moles.
For a large amount of nitrogen diffusion of pure nitrogen in the same temperature range, these calculated activation energies can be compared with the values of 168 kilojoules/moles.
The lower-than-expected computational values currently studied are likely to be the result of the development of high diffusion channels at the interface between n-Al and O2.
Low-density high manganese and aluminum steel are being considered for tough and wear-resistant automotive components and ballistic armor plating.
These steel can be considered a lightweight alternative to mining and ground components.
For example, if Fe-30Mn-9A1-0.
9C alloy with a low density of 15% directly replaces SAE 8620 steel track shoes for Bradley combat vehicles (BFV)
Save about 800 pounds in weight.
However, the mechanical properties of cast Fe-Mn-Al-
Calloys vary by composition, age
Hardness and cleanliness of steel.
Aging hardening greatly improves the strength of the cast alloy, but greatly reduces the hardening, toughness and wear resistance of the processing.
Surface modification is usually used to greatly improve the wear, fatigue and corrosion resistance of steel.
One of the most effective surface treatments to improve wear resistance is the nitrogen process, which produces a hard "white layer" consisting"]--[Fe. sub. 2](C,N)and/or y -[Fe. sub. 4]N.
Nitridingoften is used to greatly improve the wear resistance and corrosion resistance of steel.
The traditional gas and salt bath infiltration process will release toxic gases and pollute the environment.
Although the plasma nitrogen is much cleaner, the cost is very high and expensive equipment needs to be used.
Nitrogen treatment of high manganese and aluminum steel with gas nitrogen roots may be a cost effective method to produce hard and wear-resistant aluminum nitride layers.
Manganese steel in-
Casting conditions, the usual practice is to treat these steel in solution at temperatures up to 2, 012F (1,100C).
This solution treatment can be carried out in a nitrogen atmosphere to produce a wear-resistant surface coating at very little additional cost.
In the case of high manganese and aluminum steel, it no longer exists in the form of [but in the form of nitrogen aluminum]Fe. sub. 3]N.
As we all know, the hardness of nitrogen increases with the increase of the amount of nitrogen, and it is reported that the hardness of nitrogen and aluminum is 25.
6 GPa, much higher [Fe. sub. 3]N (11. 2-12. 4 GPa).
In the current study, aluminum and silicon pair Fe-
30Mn steel was determined.
From the results of the study, the steel test sample was treated as 1, 92f (1,050C)
Two hours later, it quickly went out in ice water.
Polish the surface of the specimen to 0. 3 [micro]
M is completed and cleaned in ethanol before the nitrogen.
At a temperature of 1,652-2,012F (900-1,100C)under 99.
9% pure N2, the furnace is cleaned for 20 minutes to eliminate oxygen before loading the sample.
The cross-section of the sample was characterized by optical gold Xiangxue.
Field emission scanning electron microscope (SEM)
Energy dispersion-
Ray spectrum (EDS)
Used to characterize the morphology and chemical composition of the reaction layer.
The results of chemical analysis show that the composition of the steel mainly varies depending on the content of aluminum and silicon.
At 1, 92f, the microstructure of the corresponding steel after two hours of solution treatment (1,050C)
As shown in Figure 1, before the nitrogen process3.
The structure is similar, all the steel is 100% stainless steel, only a small amount of primary iron body Island was found in C steel.
Spacing of secondary branch crystal arms (SDAS)
, Similar between steel measured between 50 and 75 pm.
The 8-hour cycling process was carried out at 1,652, 1, 832 and 2, 012F (900, 1, 000 and 1. 100C)
Three different types of aluminum and silicon steel. Figures 4a-
D shows optical Microphotograph of polished section of B Steel (8. 8% A1 and 1. 6% Si)and Steel C(6% Al and 1. 6% Si)
After two to six hours of nitrogen treatment at 1, 65f (900C).
In 1, 65f after 2 hours (900C)
The depth of development of steel C is twice the depth of nitrogen and aluminum in steel B.
For two aluminum-containing steel, the depth of the aluminum-nitrogen layer increases with the increase of the nitrated time, after 6 hours at 1, 65f (900C)
For B and C Steel, the depth measurement of the alumina layer is 170 pm and 230 pm on average.
Increase the process temperature to 1, 832F (1,000C)
The dynamics of nitridingprocess were added, and after 6 hours the average depth of aluminum nitdel was increased to 200 [micro]
As shown in figure 4, m in B steel and 370 pm in C Steel (e and f).
Therefore, for a constant silicon content of 1.
6%, the aluminum content increased from 6% to 8.
8% results in a reduction in the depth of the nitrogen-aluminum layer at all times and temperatures.
However, for the constant aluminum content of 8.
8%, silicon from 1. 1% to 1.
6% only shows a slight decrease in the depth of the nitrogen-aluminum layer.
The morphology of aluminum nitrogen looks similar between heat treated steel, and it appears to precipitate and grow along the crystalline direction.
Secondary electronic image of Alumina coating in steel (8. 8% Al and 1. 1% Si)and Steel B (8. 8% Al and 1. 6% Si)
At 1, 65 F, after 8 hours of nitrid (900C)
As shown in figure 5 (a and b)andFigures 5 (c and d).
Shell depth and plate-
Between two different silicon-containing steels, the structure of alumina is similar (Figure 5).
Secondary electron micrograph of B steel and C steel as shown in Figure 6, after 8 hours of nitrogen treatment at 2, 012F (1,100C).
In SteelB, the nitrogen layer consists of long, usually thinner plates with high density, with an average spacing of less than five o'clock P. M (
Depending on the plane in Poland)
As shown in Figure 6 (a and b).
In C Steel, the density of alumina in the reaction layer is much smaller, and the average spacing between plates is greater than ten o'clock P. M. , as shown in Figure 6 (c and d).
However, the plate thickness of C steel is larger, at 2, 012F, after 8 hours, the shell depth is almost 200 pm larger than that of B Steel (1,100C).
As shown in Figure 6, less flaky alumina arrangement was observed in C Steel (d).
It is found that the average composition of alumina precipitate changes with temperature and steel composition.
For all single plates sampled, the chemometric ratio of aluminum to nitrogen is close to 1.
At 1, 832F, A steel and C steel after six hours and eight hours of nitrogen, the OHS matrix chemistry between the plates (1,000C)and 2,012F (1,100C)
It is almost completely depleted of aluminum and is rich in manganese and silicon, which may also improve wear resistance.
For steel with a aging period of more than 6 hours, about 10-20 [micro]
As shown in figure 5d, the m composite oxide layer is found on the surface above the nitrogen layer.
The presence of oxide layers suggests that not all oxygen is eliminated from the furnace.
However, in the process of nitrogen, the oxide layer did not develop until after the extension of time, and the formation of aluminum nitride has been favored because the solubility and diffusion of gap nitrogen in steels are much higher.
Figure 7 shows the depth of the nitrogen-aluminum layer as a function of time and temperature.
Depending on the time and temperature, the thickness of the Alumina coating between 200 and 550 pm can be achieved.
No. 8 Steel A and B. 8% Al and 1. 1% Si to 1.
6% Si shows similar coating thickness at all times and temperatures.
Although it is known that silicon will reduce the solubility of nitrogen substitutions, the silicon level will increase from 1 in the current study. 1% to1.
6% has little effect on the depth of the alumina layer or the apparent density of the precipitated plate.
However, the content of aluminum was increased from 6% to 8.
8% produced a very fine dense array, but significantly reduced the depth of the nitrogen-aluminum layer.
It also reduces the diffusion coefficient of nitrogen by 50%, and in the temperature range of 1,652-the activation energy increases from 64 kilojoules/moles to 78 kilojoules2,012F (900-1,100C).
Current research results show that high manganese and aluminum-deformed steel can be nitrated in a gas-nitrogen atmosphere to produce hard and wear
In the depth of up to 550 pm, the resistance layer of AIN.
The amount of silicon is from 1. 1% to 1. 6%Si ina Fe-30Mn8. 8A1-0.
9C steel has no statistical effect on the diffusion of nitrogen in the temperature range of 900 to 1100C.
However, the increase in aluminum content in high manganese steel increases the activity of nitrogen and reduces the solubility and diffusion coefficient of nitrogen.
ESS this article is based on "nitrogen of light weight manganese and aluminum steel "(15-036)
Made its debut at 119 Metal Casting Conference.
Texas State University Laura batlitt and Sabra Cerino