Color-Metallographic Characterization of Alloyed White Cast Irons Ni-Hard Type

The Ni-hard alloys white-cast irons are generally used for high wear work. Among them, those with better impact resistance because of its low carbon content compared to the rest of the family, are studied in this paper. One experimental technique of characterizing the metallic materials is the microstructural study. Several metallographic attacks intended to reveal qualitatively each microconstituent that forms the alloy, as well as the segregation and solidification structure of casting, are studied in this article. The use of color metallography is fundamental in this case to distinguish clearly the microconstituents. The main objective of this paper is to propose a series of attacks that identify each one of the microconstituents present in the alloy that has not been reported up to date.

A Comparison between Anodizing and EBSD Techniques for Primary Particle Size Measurement

Proper understanding and knowledge of primary particle or grain size is of paramount importance in manufacturing processes as it directly affects various properties including mechanical behavior. Application of optical microscopy coupled with etching techniques has been used conventionally and in conjunction with color metallography (polarized microscopy) has been the preferred method for grain size measurement. An advanced technique as an alternative to light microscopy is using electron backscatter diffraction (EBSD). A comparison is made between these two techniques using Al-7Si alloy produced with various casting techniques to highlight the cost and time of the sample preparation and analysis for both techniques. Results showed that color metallography is certainly a faster technique with great accuracy and a much cheaper alternative in comparison with EBSD.

Application of color etching to study the microstructure of TRIP steel after laser remelting

TRIP type steels have a multi-phase structure, which includes such phases as: aus-tenite, bainite, ferrite and martensite. The presence of so many co-existing phases creates difficulties in their accurate identification. One of the methods used to identify the components of the microstructure is color metallography. Methods of color met-allography in contrary to some methods of microstructure identification (e.g. TEM, EBSD) are simple to use, cheap and not very time-consuming. However, there are still no detailed recommendations on the use of this method. The paper examines the pos- sibilities of application of colored etching methods, to distinguish the components of the microstructure of the as-received material and the welds of the TRIP type steel. Light microscopy methods were used for the study. The obtained results allow for a qualitative distinction of individual components of the microstructure.

Simulated HAZ continuous cooling transformation diagram of a bogie steel of high-speed railway

Simulated HAZ continuous cooling transformation (SH-CCT) diagram presents the start and end points of phase transformation and the relationships of the microstructures of HAZ, temperature and cooling rates. It is often used to assess the weldability of materials. In this paper, a weathering steel Q345C which is widely used in the bogies manufacturing was studied. The cooling times from 800[Formula: see text]C to 500[Formula: see text]C ([Formula: see text]) were from 3 s to 6000 s, aiming to study the microstructures under different cooling rates. Different methods such as color metallography were used to obtain the metallography images. The results show that ferrite nucleates preferentially at the prior austenite grain boundaries and grows along the grain boundaries with a lath-like distribution when [Formula: see text] is 300 s. Austenite transforms into ferrite, pearlite and bainite with decreasing [Formula: see text]. Pearlite disappears completely when [Formula: see text] s. Martensite gradually appears when [Formula: see text] decreases to 30 s. The hardness increases with decreasing [Formula: see text]. The SH-CCT diagram indicates that the welding input and [Formula: see text] should be taken into consideration when welding. This work provides the relationships of welding parameters and microstructures.

Welding Effects on the Mechanical Integrity of a Trip800 Steel: a Comparison of Laser Co2 and Gmaw Processes/ Wpływ Spawania Na Integralność Mechaniczna Stali Trip800: Porównanie Spawania Laserowego Ze Spawaniem Elektrodą Topliwą

In this work a strip of a transformation induced plasticity (TRIP) steel was welded using gas metal arc welding (GMAW) and Laser CO2 welding (LBW) processes and the resultant strength and ductility of the welded joints evaluated. It was found that LBW lead to relatively high hardness in the fusion zone, FZ where the resultant microstructure was predominantly martensite. The relative volume fractions of phases developed in the welded regions were quantitatively measured using color metallography combined with X-ray diffraction analyses. It was found that the heat affected zone, HAZ developed the maximum amount of martensite (up to 32%) in the steel welded using LBW besides a mixture of bainite, retained austenite and ferrite phases. In contrast, a relatively low percent of martensite (10.8%) was found in the HAZ when the GMAW process was implemented.

Utilization of Color Metallography in Characterization of a Modified SAE 4118H Steel Submitted to Isothermal Treatments

A modified SAE 4118H steel was subjected to isothermal treatments between 700 °C and 400 oC every 50 °C range, with the intention of evaluating the decomposition of austenite at constant temperature. It was varied time of stay in the isothermal treatment between 15 and 28800 seconds depending on the treatment temperature. After each isothermal treatment and standard metallographic preparation, the samples were etched with color metallography reagents for revealing the microstructure obtained. At temperatures of 700oC to 550°C the steel showed microstructure composed of ferrite and pearlite. Between 500oC and 400°C bainitic microstructure was quickly formed. The reduction of treatment temperature provided finer microstructures, which increased the hardness of steel. With the use of color metallography reagents, excellent contrast for determining the volume fraction of microstructural constituents formed isothermally was obtained, helping the study of isothermal decomposition of austenite.