1. Determination method:
There are currently two methods for detecting surface contamination of titanium and titanium alloys, one is the metallographic method and the other is the hardness method.
The formulation of this standard is mainly based on the actual domestic application situation. After comparative analysis, it is believed that the application of metallographic method is relatively common and an effective method, so the metallographic method is included in the determination standard.
2. Sample preparation:
Scientific provisions are made for the preparation of specimens, such as status, direction, and operation matters.
3. Corrosion of microscopic specimens:
For the proportion of corrosive liquid, in addition to the two proportions in prEN 2003-9, a proportioning liquid currently commonly used in China was also selected. Among them (1) and (2) are the proportions specified in prEN 2003-9, and (3) is the proportion commonly used in China.
(1) Corrosive agent 1: 2%~5%HF (concentration: 40%~42%) + 40%~50% C3H8O+ H2O (remainder).
(2) Corrosive agent 2: 2%～5%HF (concentration: 40%～42%) + 10%～20% HNO3 (concentration: 65%～68%) + H2O (remainder).
(3) Corrosive agent 3: First use 2% HF (concentration: 40% ~ 42%) + 4% HNO3 (concentration: 65% ~ 68%) + H2O (remainder), and then use 2% NH4HF2 aqueous solution.
4. Microscopic examination
The inspection magnification is specified. After the sample is etched, the structure is observed under an optical microscope with a magnification of 100 to 500 times.
5. Evaluation
The white layer appearing on the edge of the sample microstructure may have a high-density bright a phase, indicating the presence of surface contamination.
6. Surface pollution layer thickness test
Use a metallographic microscope to detect the microstructure of the sample. When there is a surface contamination layer, use a microscope with a measuring scale eyepiece to observe and calculate the actual size of the thickness from the white layer to the normal matrix area. The thickness of the pollution layer is represented by the deepest part of the pollution layer size.
7. Test report
The content of the test report is specified in detail.
