Hårdhedstest efter PWHT

Hardness tests after PWHT are essential for understanding the quality of welds. A drop weight tester measures impact toughness to assess its impact resistance and weld metal impact resistance.

Postweld heat treatment (PWHT) increases the hardness of EB weld metal (WM) by precipitation of Ti-C,O,N precipitates in its as-welded state [1], but impact toughness at 77 K is not recovered to that of BM [2, 3].

Rockwell Hardness Test

The Rockwell hardness test is an efficient and straightforward method of hardness measurement that produces immediate hardness results. It can be applied to various materials and forms an essential part of quality assurance testing processes. Unlike Brinell and Vickers hardness tests, which require secondary dimensional measurements before measuring hardness values directly, Rockwell can measure hardness instantly within seconds using direct hardness readings.

The test begins with a minor load to establish zero position before applying a major load and recording its depth of indentation as part of its results; this data can then be used to calculate Rockwell scale numbers.

Errors may occur in testing procedures and equipment, compromising final results. Proper preparation of test specimen is paramount in order to achieve accurate test results; as such, surface conditions depend on the load applied; regular Rockwell scales can use ground surfaces while more demanding scales require polished or lapped surfaces for testing. It’s also imperative that indenters remain in good condition to provide accurate test results.

Brinell Hardness Test

Brinell method was initially devised in 1900 by Swedish engineer Johan August Brinell. This standardized hardness test can be used to assess various metals, from aluminum and soft alloys (at lower load levels) through cast iron and steels (at higher loads).

This test involves pressing a carbide indenter ball against a sample surface with an applied force, which is held for an extended period. Any impression left behind by this action is then measured across two perpendicular diameters before reference charts provide hardness readings.

This technique may lead to errors if the testing machine is not calibrated correctly or environmental conditions do not match. Furthermore, high test loads in the macro range can cause plastic deformation and wall formation, making evaluation difficult.

Vickers Hardness Test

Vickers hardness tests provide the ideal balance of precision and adaptability, making it a valuable tool for materials scientists and metallurgists alike.

Vickers test involves pressing a pyramid-shaped indenter with a prescribed test load into the surface of a specimen at various dwell times and taking measurements after removal from its impact point.

Controlling the testing environment when conducting a Vickers test is key to producing consistent results. Ensuring the indenter is aligned correctly and vibrations are avoided can help ensure accurate data.

Maintaining a uniform indentation size when testing materials’ hardness is also vital, enabling you to compare test results across samples of the same material. Furthermore, keeping dwell time constant will prevent variations in size or hardness calculation which makes data more reliable and simpler to understand.

Microhardness Test

The Microhardness Test measures metal deformation resistance using static indentation. The hardness number obtained is calculated as an inverse of the force (kgf) required to produce it; making this method ideal for testing thin films, surface coatings, small regions of composite samples or platings as well as case hardening, carburization, grind burns or any surface contamination that might exist.

Undergoing this test involves applying a diamond indenter with a square-based pyramid shape for a specified time to produce an impression on a sample material, then measuring under microscope its hardness value from that impression.

Compare to Rockwell, Brinell and Vickers tests, microhardness requires sectioning specimens in order to achieve small enough indents for indenter use. Consistency between tests may be difficult due to various indenter shapes used. Our Tru-Blue Micro VT machine was specifically created to mitigate this challenge by offering both Vickers and Knoop testing from one interchangeable turret turret.