Metallography Testing

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Metallography Testing

Metallurgical Testing typically uses microscopy to provide important information about the structure and properties of metal and alloy samples. These services are also called Metallography Evaluation, Metallographic Examination and Metallurgical Analysis.

The metallurgists at W I Met-Lab have deep expertise in Metallographic preparation and examination to evaluate the characteristics of metals. They are highly skilled to assess a particular material’s heat treatment condition, microstructure, and forming process. The team undertakes macro and micro examination including Weld Examination, Case Depth and Decarburization Measurement, Micro Hardness Testing and Coating/Plating evaluation. 

The Metallography department employs the Inverted Metallurgical Microscope and Stereo Zoom Microscope with an Image Analysis System. The technical team has indigenously developed microstructure characterizer software that assists with the analysis of images to determine Microstructural degradation due to creep. The software can also calculate the graphitization, depth or width of decarburization, phase/volume percentage, grain growth, inclusion rating, particle size, volume percentage, particle count, porosity and coating thickness

Metallography Tests at W I Met-Lab 

  • Micro Examination : This is performed on samples that are either cut to size or mounted on a resin mould. These samples are polished to a fine finish, typically a one-micron diamond paste and prior to an examination on the metallurgical microscope, it is usually etched in an appropriate chemical solution. Micro-examination is performed for a number of purposes, the most common of which is to assess the structure of the material. Many routine tests such as phase counting or grain size determinations are performed in conjunction with micro-examinations.
  • Macro-Examinations : In Macro-etching a specimen is etched and macro-structurally evaluated at low magnifications. It is a frequently-used technique for evaluating steel products such as billets, bars, blooms and forgings. There are several procedures for rating a steel specimen by a graded series of photographs, showing the incidence of certain conditions and is applicable to carbon and low alloy steels. A number of different etching reagents may be used depending upon the type of examination. Steels react differently to etching reagents because of variations in chemical composition, the method of manufacturing, heat treatment, and many other variables.
    Macro-Examinations are also performed on polished and etched cross-sections of welded material. During the examination, a number of features can be determined including the weld run sequence, which is vital for weld procedure qualifications tests. Apart from this, any defects on the sample are assessed for relevant specifications and compliance. Slag, porosity, lack of weld penetration, lack of sidewall fusion and poor weld profile are among the features observed in this type of examination. It is procedural to identify such defects, either by standard visual examination or at magnifications of up to 20X. It is also routine to photograph the section to provide a permanent record and this is known as a photomacrograph.
  • Weld Examination : Metallographic weld evaluations take place in many forms. In its most simple format, weld deposits can be visually examined for large-scale defects such as porosity or lack of fusion defects. On a micro scale, the examination can take the form of phase balance assessments from weld cap, weld root or can even be checked for non-metallic or third phase precipitates. Examination of weld growth patterns is also used to determine the reasons for poor mechanical test results.
  • Case Depth - Case hardening may be defined as a process for hardening ferrous materials in such a manner that the surface layer (known as the case) is substantially harder than the remaining materials (known as the core). This process is controlled through carburizing, nitriding, carbonitriding, cyaniding, induction, and flame hardening. The chemical composition and mechanical properties are affected by these practices. The methodology utilized for determining case depth can either be chemical, mechanical or visual and the appropriate one is selected based on specific requirements.
  • Decarburization Measurement : This method is designed to detect changes in the microstructure, hardness or carbon content at the surface of steel sections due to carburization. To determine the depth, a uniform microstructure, hardness or carbon content of the specimen interior is observed. This method detects surface losses in the carbon content due to heating at elevated temperatures.
  • Coating / Plating Evaluation (ASTM B487) : A coating or plating application is used primarily for the protection of the substrate. Thickness is an important factor in the performance of the coating or plating. A portion of the specimen is cut, mounted transversely and is prepared in accordance with acceptable or suitable techniques. The thickness of the cross section is measured with an optical microscope. Cross-sectioned metallographic examinations of substrates with plating, surface evaluations, and thickness measurements can aid in the evaluation of plating.
  • Grain Size Determination (ASTM E112, IS 4748) : In order to establish a scale for grain size, ASTM E112 shows charts with outline grain structures for various dimensions. These universally accepted standards range from ASTM NO. 00 (very coarse) to 10 (very fine). A material's grain size is important as it affects its mechanical properties. In most materials, a refined grain structure gives enhanced toughness, and alloying elements are deliberately added during the steel-making process to assist with grain refinement. Grain size is determined from a polished and etched sample, using optical microscopy at a magnification of 100X or 500X.
  • Other Metallography test offers like Inclusion test, Graphite size, type & distribution in cast irons, Quantitative Metallography to know the percentage of particular phase % ferrite in Duplex stainless steel.

We can offer all above mentioned tests under all third party inspection agencies

For more information about our Metallography Testing, or to request a quote, contact us today.