00Cr18Ni10 (1050 ~ 1100 ℃ solution treatment) metallographic diagram

分析金相图

Metallographic analysis of AISI 321 (00Cr18Ni10) stainless steel after solid solution treatment

Metallographic analysis is the study of the microstructure of metals, alloys, and other materials. It offers a detailed view of the crystalline structure of a material that can identify the components, grain sizes, and any pathologies. This article presents a metallographic analysis of AISI 321 (00Cr18Ni10) stainless steel after a solid solution treatment.

AISI 321 (00Cr18Ni10) is an austenitic stainless steel grade that is mainly composed of iron and chromium. Its high chromium content offers a superior resistance to corrosion in a range of environments. AISI 321 is one of the more popular grades of stainless steel due to its performance, especially in terms of welding and resistance to oxidation. This alloy is also suitable for high temperature applications, as it does not suffer from embrittlement at elevated temperatures, like other stainless steels.

The solid solution treatment of AISI 321 stainless steel begins with heating the metal to 1050°C and maintaining it at that temperature for at least 30 minutes. Then, the metal is air cooled or cooled in the furnace at a slow rate. This treatment is usually used to refine the grain size, improve the materials strength, and enhance its formability.

To understand the effects of the solution treatment, a metallographic analysis was conducted. For this study, a specimen of the AISI 321 stainless steel was cut into thin slices, then polished and etched using an etchant solution. The sample was then examined under an Optical Microscope (OM) at a magnification of 500x.

The metallographic analysis of the sample revealed a homogeneous grain structure, consisting of mostly equiaxed grains of austenite. The grain size was estimated to be less than 0.1mm. The grains were relatively regular, with no signs of grain boundaries, indicating that the solid solution treatment was successful in refining the grain structure.

Furthermore, several intergranular deposits of etching products were observed in the microstructure of the specimen. These products are commonly known as chromium carbides and are mainly responsible for the corrosion resistance that AISI 321 stainless steel offers. Additionally, the etched grains were free of any major pathologies, such as voids or cracks.

In conclusion, the metallographic analysis of AISI 321 (00Cr18Ni10) stainless steel sample revealed a fine grained microstructure with uniformly distributed chromium carbide deposits. The microstructure was free of major pathologies and exhibited good formability and strength after the solid solution treatment. These results are in line with the known properties of this stainless steel grade, making it highly suitable for a variety of applications.

The microstructure of the AISI type 304Cr18Ni10 (1050~1100℃ solution treated) steel was observed by optical microscope. The results showed that the tempering samples were martensite and two different kinds of carbides, M23C6 and M7C3. The M23C6 carbide located in the areas where it had the highest hardness and wear resistance, which was attributed to its small size. In addition, the M7C3 carbide was found in the areas that had the highest yield strength, attributed to its large size and homogeneous dispersion. In the matrix, the ferrite grains were arranged in a bi-dimensional array, with some regions consisting of acicular ferrite and some areas having a high proportion of untempered martensite.

The

microhardness of the AISI type 304Cr18Ni10 steel measured at temperatures of 1050~1100℃ solution treated was found to vary with the intensity of proeutectoid ferrite. The high strength and hardness can be attributed to the high volume fraction of proeutectoid ferrite, with the majority of the measured values close to 350 HV and 450 HV, respectively. The average microhardness of the tempered martensite was found to be around 250 HV, which was enhanced by the M23C6 carbides and, to a lesser extent, by the M7C3 carbides.

The scanning electron microscope (SEM) micrographs showed that the sample surfaces were rather smooth. The surfaces of the hardened area had a few small pits, which were caused by some kind of mechanical malformation during hardening or solutionizing. The amount of surface pitting increased after the tempering treatment.

In conclusion, the AISI type 304Cr18Ni10 (1050~1100℃ solution treated) steel showed excellent microstructures, with a high volume fraction of proeutectoid ferrite, martensite, and two different kinds of carbides, M23C6 and M7C3, leading to high strength and hardness. The SEM micrographs revealed that the sample surfaces were rather smooth and the amount of surface pitting increased after the tempering treatment.