ASTM G76 Standard Test Method for Conducting Erosion Tests by Solid Particle Impingement Using Gas Jets

Get Certified ASTM G76 Testing for Reliable Solid Particle Erosion Resistance Verification 

Erosive material loss degrades the performance and service life of materials in turbine components, pipelines, coatings, and other applications subjected to particle-laden gas flows. The ASTM G76 test standard establishes interlaboratory precision for a material’s erosion resistance, measured by a standardized, well-characterized jet-nozzle procedure. In the aerospace, energy, and industrial coatings markets, accredited laboratory testing supports coating development, material ranking, and quality control. ASTM G76 testing identifies the order of erosion resistance of materials considered for an application under the test conditions. 

• Material type: Engineering materials (metals, coatings, etc.) tested as flat sample panels or coupons. 
• Purpose: Erosion resistance of solid particles in controlled laboratory conditions, for screening and ranking. 
• Properties evaluated: Material loss (erosion rate), which is normally the cumulative mass loss over the course of the test. 
• Testing Method: Jet-nozzle type erosion equipment that spits a stream of gas-entrained abrasive powder at a target specimen at a controlled impingement angle, distance, and feed rate. 
• Result: Cumulative Mass Loss and Calculated Erosion Rate to rank materials under the test conditions. 
• Test Limitations: The use of any single test to assess the erosion service performance of a material is not appropriate, because the range of service conditions for erosion is very wide. 
• Environmental conditions: Analysts recognize that impingement angle, abrasive particle size, gas pressure, particle feed rate, nozzle-to-specimen distance, and carrier gas type can affect the measured erosion rate.
• Applications: Coating evaluation for turbine components, material erosion evaluation for pipelines, development of protective coatings, material formulation ranking in erosive environments. 

What are the Uses of ASTM G76 Testing?

ASTM G76 provides a method for laboratories to determine and compare the resistance of various materials to solid particle erosion under controlled and repeatable conditions. Engineers and coating developers then use the results to compare materials to be considered for erosive service applications. This standard- 

• Calculates the material loss due to gas-entrained solid particle impingement erosion.
• Carries out a screening test for the determination of the ranked erodability of materials in simulated service conditions when exposed to solid particle erosion.
• Explains one very well-described procedure in which interlaboratory results are known.
• Facilitates comparison of the erosion resistance of metals, coatings, and other engineering materials.
• Helps to compare the effect of impingement angle on the rate of erosion of ductile and brittle materials.
• Coats and develops materials for turbine, pipeline, and industrial erosive service applications. 

What Materials Can Be Tested Under ASTM G76? 

ASTM G76 is used for the erosion testing of metals, protective coatings, and other engineering materials, which are produced as flat sample panels, or coupons. The test method is suitable for materials to be placed in a service environment with erosive particles, including turbine components, pipeline surfaces, industrial equipment in particulate-laden environments, etc. The erosion rate varies significantly with impingement angle: ductile materials tend to have the lowest erosion rate at a 90° impingement angle, while brittle materials have the lowest erosion rate at very low impingement angles. An analyst verifies the expected service impingement angle before selecting the test conditions. 

Why is ASTM G76 Important? 

ASTM G76 provides a well-defined and widely characterized method for determining resistance to solid particle erosion, and available interlaboratory test results ensure confidence in the ability to get repeatable results even among accredited laboratories. The significance of this test method in the overall measurements program to assess the erosion behavior of materials depends upon several factors related to service application conditions, and the user of this test method determines the extent of correlation of results obtained with results from field performance or results obtained with other test systems and test methods. The material selection depends on the angle of impingement, and the effect of this angle can be quite different for ductile and brittle materials, so it is important to understand this. This standard is used to compare material and coating erosion resistance in controlled laboratory environments. 

ASTM G76 Testing Process and Data Collection

The testing process starts with preparing, cleaning, and weighing the specimen in order to get the baseline mass. Technicians are responsible for setting up the jet-nozzle erosion machine to achieve the desired test conditions in accordance with the impingement angle, abrasive particle size, feed rate, gas pressure, and nozzle-to-specimen distance. The powder feed system mixes the abrasive into the carrier gas stream at a fixed rate, and the gas stream is expelled for a fixed time period, usually in a series of intervals, and impacts the target specimen through a nozzle, resulting in a good degree of accuracy in mass change measurement, especially over a total test time of several hours. After each time interval of erosion, technicians clean and re-weigh the specimen to calculate the total amount of mass lost. Laboratory analysts collect mass-loss data throughout the test to determine the erosion rate and compare the tested material with other materials evaluated under the same conditions.

Common Challenges and Troubleshooting

Common issues related to ASTM G76 testing are inconsistent particle feed rate, nozzle wear that changes the velocity of particles, and poor mass loss resolution for highly erosion-resistant materials. The problems may cause measurement of the erosion rate to be distorted and make material ranking difficult. For repeated tests on the same nozzle, changes in its nozzle velocity and nozzle impingement characteristics due to nozzle wear may result in an inconsistency between test series. If the mass loss per unit testing time is very low for a particular material, the results obtained may be scattered or very small and difficult to measure on the analytical balance. Technicians minimize these problems by verifying the feed rate, monitoring nozzle condition, and using longer test times for more erosion-resistant materials. Laboratories obtain more reliable and comparable erosion-rate results by following standard procedures and using calibrated equipment.

• The laboratory reports the cumulative mass loss at the end of the erosion test, usually in milligrams.
• The laboratory records the impingement angle, abrasive type and particle size, gas pressure, particle feed rate, and nozzle-to-sample distance during testing.
• Results show the correlation between cumulative mass loss and elapsed time for the erosion test, and in many cases this relationship is a good linear fit for many materials.
• The laboratory reports that the erosion rate is very sensitive to the impingement angle and that ductile material has the lowest erosion rate at 90° while brittle material exhibits the lowest erosion rate at low impingement angles.
• Analysts determine the degree of correlation between laboratory results and field performance or results from other test methods.
• Analysts obtain reliable and comparable erosion-rate data by maintaining consistent equipment setup, verifying the feed rate, and properly handling specimens.
• Analysts use erosion-rate results to rank materials and coatings for erosive service applications.

Link to ASTM G76