Metallurgy and Materials Analysis

Failure Analysis & Investigation

ARI provides a comprehensive range of failure analysis testing and inspection services by determining root cause of failure through chemical, mechanical, and metallurgical examinations. This investigation helps and supports manufacturers, owner operators, and stakeholders to understand why a failure occurred and how to prevent a similar future failure.

We have the ability to perform the following testing and inspection services both on-site (client premises) and within our fully equipped investigative laboratories as follows:

• Visual examination to identify wear patterns, damage, corrosion, and any evidence of failure modes.
• Fractographic examination to identify the mechanism of fracture and determine the cause of undesirable cracking and failure by characterising features and patterns of a fractured surface.
• Chemical analysis to determine the material composition, element analysis, and impurity identification.
• Microstructural examination to identify materials structure and defect characteristics, as well as determine the nature and morphology of the cracks.
• Scanning electron microscopy examination to evaluate fracture surface and crack initiation and propagation sites at high magnifications.
• Tensile, hardness, and impact tests to evaluate the mechanical properties of the failed products.
• Corrosion testing and analysis to determine the corrosion rate and mechanism.
• Non-destructive testing (NDT) to detect surface and shallow subsurface discontinuities, cracks, seam, voids or materials flaws.

X-ray fluorescence spectroscopy (XRF)

The X-ray fluorescence spectroscopy (XRF) is a non-destructive analytical method used to determine the elemental composition and the grade of the alloy. Portable XRF (PXRF) is a portable form of elemental analysis instruments based on an energy dispersive principle. The PXRF is placed in contact with metallic materials and products to be analysed, and chemical analytical results are immediately apparent for material identification and verification purposes.

Using advanced portable XRF analysers, ARI offers fast, non-destructive, and accurate elemental analysis services anywhere.

Optical Emission Spectroscopy (OES)

The elemental analysis of materials is an essential parameter for the processing of metallic materials and a substantial criterion for quality, safety, and stability in the application.
Optical emission spectroscopy (OES) using Arc/Spark excitation is the most preferred method to determine the chemical composition of metallic materials used in a wide range of industries. OES is capable of analysing a wide range of essential elements at low levels, such as Carbon (C), Sulfur (S), Phosphorus (P), Boron (B), Tin (Sn), Arsenic (As), and Nitrogen (N).

In this method, the excited atoms/ions in the discharge plasma (high-energy state) create a unique emission spectrum and emit light with a wavelength specific to each element. This light is then directed into the optical systems to extract the emission spectrum and is measured using an electronic detector (photomultiplier tube), which converts light into an electric signal. The measured signal is consequently converted into concentrations of chemical elements, which provide information regarding the specimen’s chemical composition.

Using advanced portable and stationary optical emission spectrometers (OES), ARI provides accurate chemical analysis services on metallic materials both on-site (client premises) and within our advanced, equipped laboratories for:

• Determining material identification and verification.
• Verifying chemical composition from raw material to finished product.
• Determining material composition, element analysis, and impurity identification.
• Calculating equivalent carbon content (C.E) for the welding process.
• Supporting quality control processes, material selection, and failure analysis research.

Macroscopic Examination

Macroscopic examination, also known as macro test, is often accomplished at low magnification on the cross or longitudinal sections of welds to evaluate the weld quality. Moreover, the macro test is performed on fracture surface of the failed parts to determine the cause of failure and any evidence of failure modes. The macro sample is prepared using standard metallographic techniques including cutting, grinding, polishing, and etching in an appropriate chemical solution according to ASTM E407. The macrostructural properties of a weldment are then assessed according to the relevant welding standard such as ASME and AWS.

ARI metallurgical engineering team offers the following macroscopic examination services according to the relevant standards:

Weld cross-section examination to reveal:

1. Weld geometry.
2. Weld profile, weld passes and sequence.
3. Internal discontinuities such as voids, porosity, inclusions, slag, cracks, lack of weld penetration, and lack of sidewall fusion.
4. Extent of heat-affected zone (HAZ).
5. Surface defects such as undercut, inconsistent weld bead profiles, excessive throat, concave or convex weld, and weld toe angle.
6. Joint geometry defects such as root gap, root face, and misalignment.

Fractographic examination to identify:

1. All sorts of anomalies, service damage, wear marks, and cracks.
2. Corrosion damage and morphology of corrosion products.
3. Mechanism of fracture and any evidence of failure modes.

Microscopic Examination / Metallography

Microscopic examination is performed to evaluate the microstructural characteristics of the metal and alloys at a micro level. Not only does the examination of etched structures of metals and alloys provide information about how a material has been processed, but also determines if the structural parameters are within certain standards or specifications.

Using standard metallographic techniques and an advanced image analysis software, ARI offers microscopic examination services both on-site (client premises) and within our advanced, equipped laboratories in order to determine:

1. Microstructural characteristics such as grain structures, grain size, phase transformation, distribution of structural phases and impurities (metallic and non-metallic).
2. Internal discontinuities such as voids, porosity, shrinkage, inclusions and cracks.
3. Effective or total case-depth in accordance with AS 1982.
4. Material’s response to processing such as heat treatment and welding.
5. Material degradation and failure mechanisms such as corrosion.
6. Extent of carburization & decarburization.
7. Classification of graphite in cast iron in terms of type, distribution, and size.

Case-Depth Measurement

Case hardening or surface hardening is a process used to improve both the wear resistance and fatigue strength of metal parts under dynamic and/or thermal stresses. The process is accomplished by hardening the surface layer (called the case) without influencing the softer residual material (called the core). The combination of hard surface and ductility at the core is useful in parts such as gears, machine tools, bearings, shafts, automotive components, and etc. that must be very hard on the outside to resist wear but softer inside to resist impact that occurs during operation.

Case hardening methods, including induction-hardening, carburising, nitriding, carbonitriding, cyaniding, and ferritic nitrocarburizing, result in forming a thin layer of harder metal. An accurate and repeatable method is necessary to measure the hardness and thickness of the hardened layer for the quality control of the hardening process and also to confirm to the specifications. Moreover, the chemical composition and/or microstructure may be affected by any of those methods which need to be evaluated.

Using advanced testing equipment and measurement systems, ARI provides timely and accurate testing services for quality monitoring and analysis of hardened parts and products, including:

1. Determining effective or total case-depth (the thickness of the hardened layer) by the hardness travers, micrographic, and micro-hardness test methods in accordance with AS 1982.
2. Measuring the depth of the complete or partial decarburization layers by microscopic and hardness methods.
3. Measuring hardness of surface, hardened and transition zones, core as well as weld/HAZ regions and secondary phases.
4. Examining detailed microstructure of hardened parts and products.
5. Determining material composition and element analysis using optical emission spectrometer.

Corrosion Investigation

Corrosion is defined as the deterioration of a material and its properties due to an electrochemical reaction between a material and its environment. ARI has extensive experience in the investigation, diagnosis, and prevention of damage related to all types of corrosion. We also have wide experience in the assessment and remediation of corrosion issues in the field using ultrasonic, X-ray, and magnetic methods.

Having high qualified and experienced engineers and experts, ARI provides a wide range of corrosion investigation services to determine:

1. Type of corrosion, damage mechanisms, and the root cause of corrosion.
2. Corrosion rate of the metallic materials using immersion test (weight loss method).
3. Susceptibility of the wrought, nickel-rich, and chromium bearing alloys to intergranular corrosion according to ASTM G28.
4. Pitting and crevice corrosion resistance of stainless steel and related alloys according to ASTM G48.
5. Intergranular attack susceptibility of ferritic and austenitic stainless steel according to ASTM A763 and ASTM A262.

Grain Size Measurement

Grain size, also known as the particle size, is a critical parameter that defines the characteristics of metals and alloys. Grain size has a highly influence on most mechanical properties. Decreasing grain size has an advantage of both increasing the hardness, yield strength (YS), ultimate tensile strength (UTS), as well as improving the fatigue strength and impact toughness.

Having advanced microscopy equipment, ARI offers measuring the grain size of metal and alloys in accordance with ASTM E112 and AS 1733 standards by counting the number of grains inside a known area or comparison with the standard grain size chart.

Inclusion Content Test

Non-metallic inclusions are dispersed particles of various chemical compositions (i.e., oxides, sulphides, and Aluminates) which are produced during the melting and manufacturing process of steel production. The non-metallic Inclusions have a significant influence on most mechanical properties such as formability, toughness and even corrosion resistance. Therefore, determining the non-metallic inclusion content of steel products is one of the most important parameters of metallurgical quality.

Having advanced microscopy equipment, ARI offers a number of microscopic test methods for assessing the content of the non-metallic inclusion in steel according to:

AS 2197: Micrographic Assessment of the Non-Metallic Inclusion Content in Wrought Steel
ASTM E45: Standard Test Methods for Determining the Inclusion Content of Steel