Metal Testing, metals testing methods, metallographic testing, failure analysis of metal
APM Testing provides A2LA accredited (ISO 17025) laboratory services for chemical analysis of metal, mechanical testing of metal, metallographic testing of metal, failure analysis of metal, and metal material certification. In addition to metal testing, our laboratory also does plastic testing, rubber testing, oil testing, paint testing, plating testing, adhesive testing, circuit board testing, and other testing.
The most common tests performed on metal include chemical analysis (GDS), tensile properties (ASTM E8), and hardness (ASTM E18). This combination of tests provides a reasonably good baseline for a metal sample assuming that it is large enough to do all three tests, is uniform in composition, and is uniform in hardness. Depending on the application there may be other properties which are important such as corrosion resistance (ASTM B117), case depth (SAE J423), or microstructure (ASTM E407), or plating thickness (ASTM B568).
Chemical Analysis of Metal
Chemical Analysis by GDS provides a fast and relatively inexpensive method for analyzing most aluminum, brass, carbon steel, low alloy steel, cast iron, superalloy, and stainless steel materials. XRF Analysis or EDS Analysis can also be used if there is limited sample size or if elements not covered by GDS are required. We sub-contract for inductively coupled plasma (ICP) analysis on samples that don't work well with our other methods.
Mechanical Testing of Metal
Tensile properties (ASTM E8) provide useful information about the strength and ductility of a metal. Hardness testing is also useful as it can often be correlated with tensile strength and can be done on smaller samples. There are many hardness scales to choose from depending on sample size, uniformity, and industry practice. Brinell Hardness (ASTM E10) uses the largest sample but is useful for materials which are non-uniform such as cast iron. Rockwell Hardness (ASTM E18) has a range of scales covering a large hardness range and uses less material than Brinell Hardness (ASTM E10). Knoop Microhardness and Vickers Microhardness (ASTM E384) testing can be used when little sample is available or a specific area is to be measured. Plating hardness (ASTM B578) and case depth (SAE J423) measurements are examples of microhardness applications.
Metallographic Testing of Metal
The microstructure of a metal (ASTM E407) can reveal useful information about service history as well as processes such as heat treatment, forming, forging, extrusion, cold rolling, hot rolling, threading, heading, and drawing. If carbon steel is heated until it is bright red then the microstructure can be altered depending on how fast it is cooled. Quench cooling of carbon steel will generate a hard, brittle structure called martensite which can be made less brittle using a heat treating process called tempering. Slow cooling of carbon steel will result in a softer, more ductile structure of ferrite and pearlite. For cast iron samples graphite distribution (ASTM A247) has a large effect on strength if not controlled properly.
Failure Analysis of Metal
Our decades of experience and wide range of testing instruments provide a unique advantage for finding the probable root cause of a failure. Scanning Electron Microscopy (SEM) of a fracture surface can often identify the fracture initiation point, mode of propagation, and speed of propagation. A complete picture can be obtained with the addition of EDS Analysis for corrosive elements, microstructural analysis (ASTM E407), base material composition (GDS), mechanical properties, and a service history provided by the client. A detailed report with full documentation of results along with pictures illustrating defective areas is included with every failure analysis project.
Metal Material Certifications
Material specifications list specific performance requirements for different grades of metal. Material specifications differ from test methods because test methods only specify how to test for a property but do not include acceptable ranges for the test results. ASTM, SAE, and the military all publish metal certification standards.
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