Metallurgical Replication – A Forgotten Non-destructive Art?


​The process of metallurgical replication has been around for many years, and even has a standard documenting the procedure in ASTM E1351. In recent years however, it has become a less well known NDT technique for identifying metallurgical microstructures and defects.

With sustainability becoming increasingly prevalent, techniques such as replication are a vital process to assess remaining life in components whilst avoiding costly destructive methods. It has also been used by ESR Technology as a material identification technique on structures of heritage, allowing the type of material used in structural beams on buildings and bridges to be assessed without removing any surface material, particularly important on listed structures.

Recent projects involved replication support to Hyder Consulting on the Crossrail project in London. Occasionally unmapped or limited information was available for pipelines and sewer systems which were discovered either crossing or close to, the location of tunnel boring. Older pipelines and sewers were often constructed from cast iron which has is relatively brittle which can lead to cracking from close proximity piling. More ductile steels such as mild steels are able to withstand the piling shockwaves and hence no threat of damage exists. On several occasions ESR Technology used portable equipment to obtain replicas of the surface to determine the pipe/sewer material, on each occasion, ductile steel was identified allowing construction to continue and preventing expensive delays.



The process involves polishing a small area (25mm x 50mm) on the surface of the material with portable battery powered equipment using a series of abrasive papers. A mirror finish is obtained in the final stages using diamond impregnated polishing cloths. Etchants are then used to reveal the microstructure of the material. Portable microscopy can be used directly on the component to immediately identify the material type and any possible defect such as cracking or thermal tearing. The replication aspect of the technique also allows a copy of the microstructure to be taken using acetate sheets fixed to glass slides which can then be examined in greater detail in the laboratory using optical microscopy, this also allows images to be obtained and included in communication reports.

ESR Technology regularly provide on-site support for plant shutdowns to allow defects such as cracking, tearing, creep damage and thermal degradation to be identified on a variety of plant equipment. Aside from these types of features the following can also be assessed using this technique:

• Material type

• Microstructure type

• Grain size

• Heat treatments

• Cracking (thermal tears, fatigue)

• Thermal degradation and creep

• Inclusion content

• Porosity

• Corrosion (intergranular, transgranular, corrosion fatigue)

• Weld assessment

This can all be performed on-site with portable battery powered equipment by a single forensic engineer. ESR Technology has experience working at heights, in confined spaces and on waterways and provides a preliminary answer whilst in the field. A detailed report is then provided following further detailed laboratory examination of replicas obtained.

Other surface features such as scoring, gouging, corrosion pitting can also be replicated by the use of polymer based resin replication. Portable hardness testing is another technique regularly used as part of field investigations.

If you would like more information regarding metallurgical replication or would like to discuss an issue that you feel this technique may be able to solve then contact Steve Gill on 01925 843 428 or email This email address is being protected from spambots. You need JavaScript enabled to view it..


*ASTM E1351 - Standard Practice for Production and Evaluation of Field Metallographic Replicas.

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