ISO/TS 23867:2026

Technical
Specification
ISO/TS 23867
First edition
Ultrasonic testing of hardmetals
2026-09
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Ultrasonic test block . 2
4.1 Flat-bottom hole test block .2
4.1.1 Shape and geometric tolerances . .2
4.1.2 Dimension and dimensional tolerance specification of flat-bottom hole test block .3
4.1.3 Preparation of flat-bottom hole test block .3
4.2 Reference block .5
4.2.1 Basic requirements .5
4.2.2 Reference block shape and geometric tolerances .5
4.2.3 Materials .6
4.2.4 Mixing procedure .6
4.2.5 Pressing parameter .6
4.2.6 Sintering parameter .7
4.2.7 Preparation of reference block surface (grinding and polishing) .7
5 Equipment and specification . 7
5.1 Type of equipment .7
5.2 Probe .7
6 Testing methods . 8
6.1 Testing requirement .8
6.2 Detection sensitivity .8
6.3 Detection position .8
6.4 Probe scanning form .8
6.5 Probe scanning speed .8
6.6 Evaluation of test results.9
7 Defect qualification . 9
7.1 Defect characterization .9
7.2 Defect equivalent determination .9
7.2.1 Size of the hole .9
7.2.2 DAC curves .10
7.2.3 Defect boundary and indicated length .11
7.2.4 Length of crack.11
7.2.5 Area of delamination, tungsten carbide aggregation, cobalt pool, carbon defects
and eta-phase .11
7.2.6 Area of exogenous material, under-sintered area and over-sintered area.11
8 Practical application .11
8.1 Using flat-bottom hole test block to adjust initial sensitivity.11
8.2 Practical application of defect equivalent size determination . 12
8.3 Practical application of crack defect length measurement . 13
8.4 Calculation of defect area .14
8.5 Practical application . 15
Annex A (informative) Characterization of defects .16
Bibliography . 19

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
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This document was prepared by Technical Committee ISO/TC 119, Powder Metallurgy, Subcommittee SC 4,
Sampling and testing methods for hardmetals.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Ultrasonic testing of hardmetals is a method used for judging the nature of internal defects. It is based on the
reflection characteristics of similar waveforms by comparison with the reflection waveforms of standard
test blocks with internal defects. It describes how to use high-frequency sound waves to detect micron-sized
defects such as carbon defect, eta-phase, tungsten carbide (WC) aggregates, under-sintered area, cobalt
pool, and other structural defects. The equivalent size of hole was determined by distance amplitude defect
(DAC), and the indicating length of crack was determined by judging the boundary of defect.
This document covers requirements for personnel qualification, surface requirements of the tested products,
environment and coupling agent during ultrasonic testing of hardmetals. This document also covers the
requirements for ultrasonic testing equipment performance, materials of test block, tolerance of internal
flat bottom hole, sensitivity design and defect identification.

v
Technical Specification ISO/TS 23867:2026(en)
Ultrasonic testing of hardmetals
1 Scope
This document specifies an A-type ultrasonic pulse contact method applying the ultrasonic longitudinal
wave technique to hardmetals.
This document is applicable to the ultrasonic inspection for a hardmetal rod that has a circular end face
with a diameter not less than 6,0 mm and a rod length of 40,0 mm to 380,0 mm, or a hardmetal product that
has a non-circular testing area not smaller than the coverage area of the probe (not less than 12,0 mm in
diameter) and a height of 10,0 mm to 380,0 mm.
Within the detection range specified in this document, the sound transmission energy is expressed by the
probe driving voltage, and the range is 100,0 V to 200,0 V.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
hole
defects with diameter >25 μm and depth >2,0 mm inside the product
3.2
mixed materials
mixture of tungsten carbide and cobalt in a certain proportion that is mixed with the mixture of tungsten
carbide and cobalt in another proportion
EXAMPLE A mixture of 8 % cobalt and 92 % WC is mixed with a mixture of 4 % cobalt and 96 % WC or a mixture
of 20 % cobalt and 80 % WC. A mixture of tungsten carbide and cobalt with WC particle size of 0,8 μm is mixed with
the mixture of tungsten carbide and cobalt with WC particle size of 1,8 μm.
Note 1 to entry: Alternatively, the mixture of tungsten carbide and cobalt in one particle size is mixed with the mixture
of tungsten carbide and cobalt in another particle size.
3.3
cobalt pool
specific areas inside the product where the cobalt contents are higher than the other areas
3.4
tungsten carbide aggregation
coarse agglomerates of tungsten carbide particles

3.5
clutter
grass-like reflection waveform
3.6
crack
delamination
appearance of irregular interface and gap at different depths, the interface extending to a 45° angle is
delamination
3.7
carbon defects
free carbon or graphite phase present in hardmetals
[1]
Note 1 to entry: See ISO 4499-4:2016 , Figure 4 (carburization).
3.8
eta-phase
decarburized phase present in hardmetals
[1]
Note 1 to entry: See ISO 4499-4:2016 , Figure 5 (carburization).
3.9
under-sintered area
area in which the product does not reach the required properties due to the sintering temperature being too
low or the sintering time being too short
Note 1 to entry: It mainly shows a large quantity of 10 μm to 25 μm pores.
3.10
over-sintered area
area in which the coercive force and the density of the product are reduced due to the sintering temperature
being too high or the sintering time being too long
Note 1 to entry: It normally shows 30 % to 50 % lower strength.
4 Ultrasonic test block
4.1 Flat-bottom hole test block
4.1.1 Shape and geometric tolerances
The shape and geometric tolerances of a test block with a hole on the flat bottom are shown in Figure 1.

Dimensions in millimeter
Figure 1 — Flat-bottom hole test block
4.1.2 Dimension and dimensional tolerance specification of flat-bottom hole test block
The dimension and dimensional specification of a flat-bottom hole test block are shown in Table 1.
Table 1 — Size and tolerance of flat-bottom hole test block
Hole depth in the flat Hole diameter in the
Detected depth Height (or length), H Diameter, ØD
bottom, h flat bottom, Ød
mm mm mm
mm mm
10,0-20,0 20,0 ± 0,1 30,0 ± 0,1 10,0 ± 0,3 0,5 ± 0,05
>20,0-85,0 85,0 ± 0,3 30,0 ± 0,1 10,0 ± 0,3 0,5 ± 0,05
>85,0-150,0 150,0 ± 0,5 20,0 ± 0,1 10,0 ± 0,3 0,8 ± 0,05
>150,0-380,0 380,0 ± 1,0 10,0 ± 0,1 — —
4.1.3 Preparation of flat-bottom hole test block
4.1.3.1 Materials
4.1.3.1.1 Grain size
The average grain size of flat-bottom hole test block material is shown in Table 2.
Table 2 — Average grain size of flat-bottom hole test block
Applicable average grain size
Average grain size of the test block
range
μm
μm
1,2 ≤2,0
2,4 >2,0
4.1.3.1.2 Composition
The raw material composition of the test block is shown in Table 3.

Table 3 — Raw material composition
WC Co Average particle size of WC
Classification
(wt. %) (wt. %) (μm)
I 92 8 2,0
II 80 20 10,0
4.1.3.2 Mixing procedure
Ball mill I and II respectively; after ball milling, add 2 % paraffin into two powder mixtures, then apply
screen sieving and drying. The ball milling parameters of the powder mixture are shown in Table 4 (300L
rotary ball miller).
Table 4 — Ball milling parameters
Milling rod specification Ratio of solid to liquid Ethanol purity
Ratio of milling rod to
powder
mm kg/L %
Ø10,5×17,0 3,0 0,3 90,0
Materials Rotational speed Ball milling time
—
(kg) (r/min) (h)
300,0 30,0-40,0 24,0 —
4.1.3.3 Ready to press (RTP) characteristics
The RTP characteristics are shown in Table 5.
Table 5 — RTP performance
Apparent density
Pressing pressure
g/cm (Reference)
Classification
Pa
Typical value Range
I 2,0 1,5-2,5 1,5×10
II 2,5 2,0-3,0 1,3×10
4.1.3.4 Pressing parameter
The pressing conditions of various blocks are shown in Table 6.
Table 6 — Pressing conditions
Maximum Holding
Height Diameter Shrinkage Piece weight
pressure time
Classification
mm mm ratio kg
Pa s
20,0 30,0 1,25 0,83
...