ENGINEERING - RCFA/METALLOGRAPHY
ROOT CAUSE FAILURE ANALYSIS
Root cause failure analysis is a logical, structured, and deductive methodology (inclusive of but not limited to the sections listed here) that can be applied to various mechanical and process equipment. By identifying the root cause(s) of failure, suitable recommendations can be generated to prevent future recurrences and mitigate "band-aid" maintenance. Failure analysis identifies all causal factors such as mechanical, chemical, environmental, technical and physical that are contributory to failure. Equipment failure results in losses to industries with respect to downtime, human injury, environmental effects and asset damage.
This is a non-destructive method of sampling topography for use in microstructural analysis to either verify metallurgical properties or the surface trend metallurgical degradation. As a negative relief on a plastic film, replicas are prepared with the replication technique outlined in ASTM E1351.
SCANNING ELECTRON MICROSCOPY (SEM)
The scanning electron microscope (SEM) uses a focused beam of high-energy electrons to generate a variety of signals at the surface of solid specimens. The signals that derive from electron-sample interactions reveal information about the sample including external morphology (texture), chemical composition, and crystalline structure and orientation of materials making up the sample. Areas ranging from approximately 1cm to 5 microns in width can be imaged in a scanning mode using conventional SEM techniques (magnification raging from 20X to approximately 300,000X, spacial resolution of 50 to 100 nm).The SEM is also capable of performing analyses of selected point locations on the sample; this approach is especially useful in qualitatively or semi-qualitatively determining chemical compositions, crystalline structure and crustal orientations.
SEM EDS (Nano) ANALYSIS
SEM EDS (Energy-dispersive X-ray spectroscopy) or Nano-analysis refers to techniques for determining the atomic structures of materials, especially crystals. The electron microscope is commonly used for nano-analysis and involves characterising atoms and molecules at surfaces and interfaces, both at the micro scale and nano scale.
OPTICAL EMISSION SPECTROMETRY (OES)
Optical Emission Spectroscopy is a well trusted and widely used analytical technique used to determine the elemental composition of a broad range of metals. It requires a one (1) inch square minimum of sample to perform said analysis and is a destructive test method. OES Operates on the X-Ray Fluorescent (XRF) technique which can analyse a wide range of elements from Lithium to Uranium in solid metal examples covering a wide concentration range, giving very high accuracy, high precision and low detection limits.
POSITIVE MATERIAL IDENTIFICATION (PMI)
Positive Material Identification is the analysis of metallic alloy to establish composition by reading the quantities by percentage of its constituent elements. PMI operates on the same XRF principle as OES but is a non-destructive method that can be performed on in situ equipment. Minimal surface preparation with respect to material testing is required. Limitations of PMI include the non-detection of Carbon, Sulfur and Phosphorus elements. Macrohardness testing can be used in conjunction with this technique. Knowing the exact composition and grade of an alloy enables suppliers, plant workers, and other responsible parties in the chain of custody of components to match alloy specifications that are chosen for their specific properties such as heat resistance, corrosion resistance, durability, etc. It guarantees a material's elemental composition as required for safety compliance and quality control.
Optical Microscopy is used to study the topographic or microstructural features on polished and etched surfaces of the metal specimen at magnifications of p to 1000x
Stereoscopy is a technique used to enable a three-dimensional effect, adding an illusion of depth to a flat image. It is useful visual aid to view samples at low magnifications and can be utilized to examine macroscopic features such as cracks, pits, discolourations and morphologies of fractured surfaces on a failed sample.
Fractography is used to determine the cause of failure in engineering structures by studying the characteristics of a fractured surface. When a material failure involves actual breakage/rupture, fractography can be employed to identify the fracture origin, direction of crack propagation, failure mechanism, material defects, environmental interactions and the nature of stresses. Stereoscopic and SEM Imaging are integral to the scrutinizing of fractographic facets (be it either macroscopic or microscopic)
HARDNESS & MICROHARDNESS TESTING
Micro hardness and hardness testing is a method of determining a material's hardness or resistance to penetration. Microhardness testing will determine the conformance of the material to its respective ASTM code and therefore indicate if the material is suitable for a particular service.