Hastelloy Steel Plate Testing

Hastelloy steel plate inspection mainly conducts scientific testing and analysis on the chemical composition analysis, mechanical property testing, metallographic structure examination, corrosion resistance testing, non-destructive testing and dimension and appearance inspection, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Chemical composition analysis: This is the basis of the Hastelloy steel plate testing, aiming to precisely determine the contents of the main elements such as the nickel (Ni), chromium (Cr), molybdenum (Mo), tungsten (W) and iron (Fe), as well as the trace impurity elements such as the carbon (C), sulphur (S) and phosphorus (P) in the steel plate. By verifying whether it conforms to the designation standards (such as Hastelloy C-276, C-22 and B-2), it is ensured that the material has the expected corrosion resistance and high-temperature resistance.

Mechanical property testing: Evaluates the behaviour of the Hastelloy steel plate under the stressed states, and is the key to judging whether it can meet the structural or pressure-bearing applications. The main testing items include the tensile strength, yield strength, elongation, reduction of area and hardness (Brinell, Rockwell or Vickers) at the room temperatures and high temperatures. The data are used to verify its strength, plasticity and toughness indicators.

Metallographic structure examination: Observes the microstructures of the steel plate through the microscope, including the grain size rating, phase composition analysis and whether there are the harmful phase precipitations (such as the σ phase, μ phase and carbides). The structure uniformity and stability directly affect the corrosion resistance and mechanical properties of the material, and are the important basis of the quality assessment.

Corrosion resistance testing: The core value of the Hastelloy lies in its excellent corrosion resistance. The testing usually includes the standardized uniform corrosion testing (such as ASTM G31), intergranular corrosion testing (such as ASTM G28 Method A), pitting and crevice corrosion testing (such as ASTM G48), as well as the corrosion rate determination in the specific media (such as the sulphuric acid, hydrochloric acid and hydrofluoric acid).

Non-destructive testing (NDT): Detects the internal and surface defects of the steel plate without damaging the material. The common methods include the ultrasonic testing (UT) for checking the internal interlayers and delaminations; penetrant testing (PT) or magnetic particle testing (MT, applicable to the ferromagnetic Hastelloys) for checking the surface open cracks; and radiographic testing (RT) for checking the internal volumetric defects.

Dimension and appearance inspection: The geometric dimensions such as the thickness, width, length, flatness and camber of the steel plate are precisely measured, ensuring the conformity to the ordering tolerance requirements. At the same time, the surface is visually inspected or with the aid of the tools to check whether there are the defects affecting the use such as the cracks, folds, laps, scratches and excessively thick oxide scales.

High-temperature performance assessment: For the Hastelloy steel plates applied in the high-temperature environments, the high-temperature rupture strength, creep strength and oxidation resistance testing need to be carried out. These tests simulate the deformation and failure behaviour of the material under the long-term high-temperature stresses, providing the key data for the high-temperature equipment design.

Testing Scope

Incoming raw material re-inspection: After the plate manufacturers or end users purchase the Hastelloy steel plates, the independent verification of the incoming materials is carried out according to the purchase technical agreements and relevant standards (such as ASTM B575). This is the first gate of controlling the supply chain quality and preventing the misuse or counterfeit materials.

Production process quality control: In the manufacturing processes such as the hot rolling, solution heat treatment, pickling and straightening of the steel plate, the staged testing of the semi-finished or finished products of the various processes is carried out. For example, the mechanical properties and grain sizes are checked after the heat treatment, and the surface quality and decarburized layers are checked after the pickling.

Finished product ex-factory inspection: After all the production processes of the steel plate are completed, the comprehensive inspection that the manufacturer must carry out, to issue the material test certificates (MTC/COC) conforming to the standard requirements. The inspection scope covers all the contract-specified items such as the chemical composition, mechanical properties, non-destructive testing, dimensions and appearance.

Pre-inspection before the equipment manufacturing and installation: Before the manufacturing of the chemical vessels, heat exchangers and reactors, the testing of the cut Hastelloy steel plate parts is carried out, confirming their suitability for the subsequent cold and hot processing (such as the coiling and welding). The confirmatory testing of the base materials also needs to be carried out before the welding procedure qualification.

Safety assessment of the in-service equipment: The regular or irregular testing of the in-service Hastelloy equipment (such as the towers and pipelines) is carried out, monitoring the degradation of the material properties under the long-term corrosion, high temperatures and stresses, evaluating their remaining lives and safety, and preventing the sudden failures.

Failure analysis and accident identification: When the Hastelloy components have the failures such as the early corrosion perforation, cracking or fracture, the comprehensive retrospective testing of the plates at the failure positions needs to be carried out. Through the comprehensive analysis of the chemical compositions, metallographic structures and fracture morphologies, the root causes of the failures (such as the wrong material selection, improper heat treatment and excessive media) are determined.

Scientific research and new designation development: When developing the new Hastelloy alloys or optimizing the existing alloy compositions and processes, the systematic testing is an indispensable means of evaluating the material properties and establishing the composition-structure-property relationships, providing the data support for formulating the enterprise standards or applying for the patents.

Testing Methods

Inductively coupled plasma atomic emission spectrometry (ICP-OES): Used for the precise quantitative analysis of the chemical compositions of the Hastelloys, especially good at simultaneously determining the multiple trace elements, with the fast analysis speed, high precision and wide linear range. It is one of the mainstream chemical composition analysis methods.

Spark direct-reading spectrometry (OES): Applicable to the fast composition screening and designation identification on the steel plate sites. This method has the relatively simple sample preparation requirements, and can obtain the contents of the multiple elements except C, S and P within dozens of seconds, widely used in the incoming material inspection of the steel mills and large users.

Carbon-sulphur analyser determination method: Specially used for the precise determination of the carbon and sulphur contents in the Hastelloys. The high-frequency combustion-infrared absorption method is usually adopted. The sample is burned at the high temperatures in the oxygen flow, and the generated CO2 and SO2 are determined by the infrared detectors, with the accurate and reliable results.

Room-temperature tensile testing (ASTM E8/E8M): Carried out on a universal material testing machine. By stretching the standard specimens to the fracture, the key mechanical property data such as the tensile strength, yield strength, elongation after fracture and reduction of area are obtained. The specimens need to be cut from the specific directions of the steel plate according to the standard requirements.

Hardness testing (ASTM E10, E18, E92): The suitable hardness testing method is selected according to the thickness and state of the steel plate. The Brinell hardness (HBW) is applicable to the thicker plates; the Rockwell hardness (HRB/HRC) testing is simple; the Vickers hardness (HV) has the high precision, and can be used for the hardness testing of the thin plates or micro-areas.

Metallographic microscope and image analysis: After the mounting, grinding, polishing and electrolytic etching (such as the 10% oxalic acid solution) of the specimen, its microstructures are observed under a metallographic microscope. Combined with the image analysis software, the parameters such as the grain sizes and second phase proportions can be quantitatively measured.

Scanning electron microscope and energy spectrum analysis (SEM/EDS): Used for the higher-power micro-morphology observation and micro-area composition analysis. Particularly suitable for analysing the morphologies and compositions of the corrosion products, inclusions and precipitated phases, as well as observing the micro-features of the fractures in the failure analysis.

Testing Standards

Domestic Standards:

1. GB/T 228.1-2021, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

2. GB/T 229-2020, Metallic materials — Charpy pendulum impact test method

3. GB/T 232-2010, Metallic materials — Bend test method

4. GB/T 230.1-2018, Metallic materials — Rockwell hardness test — Part 1: Test method

5. GB/T 4340.1-2009, Metallic materials — Vickers hardness test — Part 1: Test method

International Standards:

1. ASTM B575/B575M, Standard specification for low-carbon nickel-molybdenum-chromium, low-carbon nickel-chromium-molybdenum, low-carbon nickel-molybdenum-chromium-tantalum, low-carbon nickel-chromium-molybdenum-tungsten, and low-carbon nickel-molybdenum-tungsten alloy plate, sheet, and strip

2. ASTM E8/E8M, Standard test methods for tension testing of metallic materials

3. ASTM E10, Standard test method for Brinell hardness of metallic materials

4. ASTM E18, Standard test methods for Rockwell hardness of metallic materials

5. ASTM E92, Standard test methods for Vickers hardness and Knoop hardness of metallic materials

6. ASTM G31, Standard practice for laboratory immersion corrosion testing of metals

7. ASTM G28, Standard test methods for detecting susceptibility to intergranular corrosion in wrought, nickel-rich, chromium-bearing alloys

8. ASTM G48, Standard test methods for pitting and crevice corrosion resistance of stainless steels and related alloys by use of ferric chloride solution

9. ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

10. ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Spectrometer: Including the spark direct-reading spectrometers and inductively coupled plasma atomic emission spectrometers (ICP-OES). The former is used for the fast composition analysis, and the latter is used for the high-precision and multi-element quantitative determination. They are the core equipment of the chemical composition testing.

Universal material testing machine: Used to carry out the mechanical property tests such as the tensile, compression and bending. The equipment is equipped with the high-precision load cells and extensometers, and can carry out the high-temperature mechanical property testing at the room temperatures and with the high-temperature furnaces. The data are automatically acquired and processed by the computer systems.

Hardness tester: According to the different test principles and scales, the Brinell hardness testers, Rockwell hardness testers and Vickers hardness testers need to be equipped. The Vickers hardness testers are usually combined with the micro-hardness testing accessories, used to measure the hardness of the specific phases or micro-areas.

Metallographic sample preparation and observation system: This system includes the automatic cutting machines, mounting machines, grinding and polishing machines, electrolytic polishing and etching instruments, as well as the inverted or upright metallographic microscopes. The advanced systems are equipped with the digital cameras and image analysis software, realizing the digital metallographic analysis.

Ultrasonic flaw detector: Used for the non-destructive testing of the internal defects of the steel plate. The equipment transmits the ultrasonic waves into the material through the probes and receives the reflected echoes, judging the positions and sizes of the defects according to the times and amplitudes of the echoes. It is usually equipped with the multi-channel and automatic scanning devices for the large-area plate testing.

Penetrant testing and magnetic particle testing equipment: The penetrant testing line includes the cleaners, penetrants, developers and observation light sources (such as the white light lamps and black light lamps). The magnetic particle testing equipment (applicable to the magnetic designations such as the Hastelloy B-2) includes the magnetization power supplies, yokes, magnetic particle spraying devices and observation platforms.

High-temperature creep and rupture strength testing machine: Specially used to evaluate the long-term properties of the material under the high temperatures and constant loads. The equipment can apply the constant tensile forces to the specimens under the set high-temperature environments (up to above 1200 ℃), and continuously record their deformations until the fracture. The test cycles can reach thousands or even tens of thousands of hours.