GB/T 41080-2021 English PDF (GBT41080-2021)

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GB/T 41080-2021: Metallographic inspection method for molybdenum and molybdenum alloys
GB/T 41080-2021
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.120.99
CCS H 24
Metallographic inspection method for molybdenum and
molybdenum alloys
ISSUED ON: DECEMBER 31, 2021
IMPLEMENTED ON: JULY 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions... 4 
4 Principle ... 4 
5 Reagents or materials ... 4 
6 Instruments and equipment ... 5 
7 Sample ... 5 
8 Test steps ... 5 
9 Test data processing ... 6 
10 Test report ... 8 
Annex A (informative) Typical microstructure types of molybdenum and molybdenum
alloys ... 9 
Annex B (normative) Molybdenum grain size grading chart ... 11 
Metallographic inspection method for molybdenum and
molybdenum alloys
1 Scope
This document describes the methods for metallographic inspection and grain
evaluation of molybdenum and molybdenum alloy materials.
This document applies to the metallographic inspection of sintered, hot-worked, cold-
worked molybdenum and molybdenum alloys.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 6394, Determination of estimating the average grain size of metal
GB/T 13298, Inspection methods of microstructure for metals
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T 6394
apply.
4 Principle
The samples are ground and polished to reveal grain boundaries by etching. Observe
and photograph under the microscope.
5 Reagents or materials
5.1 Oxalic acid (H2C2O4·2H2O), chemically pure.
5.2 Sodium hydroxide, chemically pure.
5.3 Potassium ferricyanide, chemically pure.
5.4 Metallographic water sandpaper.
5.5 Polishing agent: alumina polishing powder or emery polishing liquid (paste). The
particle size range is generally 1.5μm~9μm.
6 Instruments and equipment
6.1 Metallographic grinding and polishing machine.
6.2 Electrolytic polishing machine.
6.3 Metallographic microscope.
7 Sample
The sample shape and size shall be easy to grind in hand. The sample size is generally
less than 300mm2 with the inspection surface area. The height of the sample shall be
less than 15mm. It can be cut when the sample is too large. When the sample is not
suitable for holding, it can be inlaid according to the provisions of GB/T 13298.
8 Test steps
8.1 Grinding of samples
Grind the samples sequentially from coarse to fine on sandpaper with different grit sizes.
During the grinding process, it is necessary to continuously rinse with running water.
For each next step of grinding, the grinding inspection needs to be rotated 90° until all
the wear scars from the previous step are removed.
8.2 Polishing of samples
Remove wear marks from samples to achieve a mirror finish. There shall be no grinding
defects. The polishing method can be mechanical polishing or electrolytic polishing:
a) Mechanical polishing: Polish with polishing compound on a metallographic
polishing machine equipped with nylon, fine canvas or wool. Polishing time is
2min~5min;
b) Electrolytic polishing: Use electropolishing machine to polish. The recommended
parameters are shown in Table 1.
Table 1 -- Recommended parameters for polishing with different electrolytes
N2 - the number of grains measured in the field of view, in pieces;
M - the magnification of the microscope;
A - the area of the field of view, in square millimeters (mm2).
NOTE: It can choose the appropriate magnification. Make the number of grains in the test circle
greater than or equal to 50. Or use a rectangular or square test pattern.
9.2.3 Intercept point method
The intercept point method shall be used for non-uniform equiaxed grains. The intercept
point method includes the straight line intercept point method and the circular intercept
point method.
The number of intercept points PL on the calculated unit length of each field of view is
calculated by formula (3):
Where,
M - the magnification of the microscope;
Pi - the number of intercept points on the total length, in pieces;
L - the total length, in millimeters (mm).
The number of stubs NL per unit length of each field of view is calculated using formula
(4):
Where,
M - the magnification of the microscope;
Ni - the number of stubs on the total length, in pieces;
L - the total length, in millimeters (mm).
Calculate the average intercept length value according to formula (5) for each field
of view: