ISO/TS 23867:2026

• Abstract:

  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.

• Status: Published
• Publication Date: 10-Sep-2026
• ICS: 77.040.20 - Non-destructive testing of metals
• Technical Committee: ISO/TC 119/SC 4 - Sampling and testing methods for hardmetals
• Drafting Committee: ISO/TC 119/SC 4 - Sampling and testing methods for hardmetals
• Current Stage: 6060 - International Standard published
• Start Date: 11-Sep-2026
• Due Date: 27-Aug-2027
• Completion Date: 11-Sep-2026

ISO/TS 23867:2026 is an ISO Technical Specification for ultrasonic testing of hardmetals. It specifies an A-type ultrasonic pulse contact method using the ultrasonic longitudinal wave technique to inspect defined hardmetal products and to judge internal defects by comparing their echoes with reference blocks. The document gives the test blocks, equipment, scanning method and defect-evaluation rules needed for practical inspection.

What does ISO/TS 23867:2026 specify?

ISO/TS 23867:2026 specifies how to carry out ultrasonic inspection on certain hardmetal rods and other hardmetal products with suitable test areas. It also defines the inspection range, the probe driving voltage used as the sound transmission energy measure, and the way the document is organized.

The scope applies to:

• hardmetal rods with a circular end face of at least 6,0 mm diameter and a length from 40,0 mm to 380,0 mm
• hardmetal products with a non-circular testing area at least as large as the probe coverage area, with the probe coverage area not less than 12,0 mm in diameter, and a height from 10,0 mm to 380,0 mm

Within the detection range, the probe driving voltage is used to express sound transmission energy, and the range is 100,0 V to 200,0 V. In practice, that means the inspection setup is controlled through the instrument settings and the selected probe, not by a generic ultrasonic output figure.

The document is organized into:

• Clause 1 - Scope
• Clause 2 - Normative references
• Clause 3 - Terms and definitions
• Clause 4 - Ultrasonic test block
• Clause 5 - Equipment and specification
• Clause 6 - Testing methods
• Clause 7 - Defect qualification
• Clause 8 - Practical application
• Annex A - Characterization of defects

Annex	What it covers
Annex A	Typical reflection-wave patterns for defect characterization

What are the key requirements of ISO/TS 23867:2026?

ISO/TS 23867:2026 focuses on setting up a repeatable ultrasonic inspection by using defined blocks, matching the probe to the product depth, scanning the full test surface, and interpreting echoes against reference waveforms. The practical result is that operators can identify a defect type, estimate its size or length, and decide whether the indication is a hole, crack, area defect or mixed-material condition.

Test blocks and reference material

Clause 4 defines two kinds of blocks. Flat-bottom hole test blocks are used to set initial sensitivity and to build distance amplitude defect (DAC) curves. Reference blocks are used for comparing defect waveforms and for simulating specific defect types such as holes, cracks, delamination, cobalt pool, tungsten carbide aggregation, carbon defects, eta-phase, under-sintered area and over-sintered area.

Clause 4.1 gives the shape, tolerances, material preparation, pressing and sintering conditions for flat-bottom hole test blocks. Clause 4.2 requires the reference block material to be similar in composition to the inspected part and limits the noise amplitude of its reflection waveform under initial sensitivity. In practice, this means the reference material must behave acoustically like the product being inspected, otherwise the comparison is less reliable.

Equipment and probe choice

Clause 5.1 calls for a suitable ultrasonic pulse echo instrument with a small attenuate reading and gain control calibrated in decibels. Clause 5.2 links probe type, frequency and diameter to the detected depth. Twin crystal straight probes are used for the shallowest range, while single crystal straight probes are used for deeper ranges.

For users, the important point is that probe selection is not arbitrary. The document ties the probe to the inspection depth, so the setup needs to match the part thickness or inspection zone before meaningful results can be expected.

Inspection setup and scanning

Clause 6.1 sets the basic test condition: the noise amplitude in the inspected product is limited and the signal-to-noise ratio must be high enough for a clear indication. Clause 6.2 describes how to set initial sensitivity from the flat-bottom hole test block, using the reflection amplitude level and compensation based on detection depth.

Clause 6.3 says that normally only one end of the pressed surface is tested, although both ends can be tested if required. Clause 6.4 requires 100 % surface coverage with a sawtooth scan path and about 50 % overlap between scans. Clause 6.5 limits probe scanning speed to no more than 150 mm/s and requires uniform probe pressure. In practice, this means the operator must cover the whole inspection area steadily enough to avoid missed indications.

Clause 6.6 gives the basic indication rule: a defect is recognized when the first echo or the clutter amplitude exceeds 20 % of the full scale under the specified sensitivity, confirmed by repeated scans. That repeated-check approach matters because it reduces the chance of reacting to a one-off signal fluctuation.

Defect sizing and qualification

Clause 7.1 says the reflection pattern is compared with the waveforms in Annex A to identify the defect type. Clause 7.2.1 and 7.2.2 explain how hole size is determined from the DAC curves by using the defect depth and attenuator reading. If an exact match is not found, the nearest reference is used and the difference in attenuator reading is applied.

Clause 7.2.3 gives the method for finding defect boundary and indicated length by moving the probe until the echo drops to 20 % of full scale or the clutter disappears. Clause 7.2.4 says crack length is taken from the maximum measured length. Clause 7.2.5 and 7.2.6 give area-based evaluation for delamination, tungsten carbide aggregation, cobalt pool, carbon defects, eta-phase, exogenous material, under-sintered area and over-sintered area. In practice, this is the part that turns an echo image into a usable dimension for acceptance, sorting or further investigation.

What terms does ISO/TS 23867:2026 define?

• Hole - A defect inside the product with a diameter greater than 25 μm and a depth greater than 2,0 mm.
• Mixed materials - A mixture of tungsten carbide and cobalt in one proportion mixed with the same mixture in another proportion.
• Cobalt pool - A local area inside the product where the cobalt content is higher than in surrounding areas.
• Tungsten carbide aggregation - Coarse agglomerates of tungsten carbide particles.
• Clutter - A grass-like reflection waveform used to describe certain defect echoes.
• Crack - An irregular interface and gap at different depths; the document also uses delamination for the same defect form when the interface extends at a 45° angle.
• Carbon defects - Free carbon or graphite phase present in hardmetals.
• Eta-phase - A decarburized phase present in hardmetals.

Who uses ISO/TS 23867:2026?

ISO/TS 23867:2026 is used by ultrasonic testing personnel, quality control staff, process engineers and laboratory technicians in hardmetal and powder metallurgy production. It is also useful for buyers, inspectors and technical managers who need a common method for checking internal defects in hardmetal rods and shaped products.

In practice, users apply it for incoming inspection, in-process control, defect investigation and comparison of parts against reference blocks. It is especially relevant where the decision depends on whether an indication behaves like a hole, crack, delamination, area defect or mixed-material region.

What does the ISO/TS 23867:2026 document contain?

ISO/TS 23867:2026 contains figure-based descriptions of the flat-bottom hole test block and the reference block, along with tables for dimensions, grain size, raw material composition, ball milling, ready to press (RTP) performance, pressing conditions, sintering parameters, probe selection and initial sensitivity. It also includes DAC curves for different probe frequencies and grain sizes, which support hole sizing by comparison with reference echoes.

The document gives practical waveform examples for holes, cracks, tungsten carbide aggregation, cobalt pool, exogenous material, carbon defects, eta-phase, under-sintered area and over-sintered area. Annex A groups these waveforms so the operator can compare a live indication with a characteristic pattern.

It also shows how to use the standard in practice: adjust initial sensitivity, identify defect type, measure crack length, and calculate defect area when the indication is area-like. For a reader, that means the document is not only a description of an inspection principle - it is also a working guide for setup, interpretation and measurement.

Technical
Specification
ISO/TS 23867
First edition
Ultrasonic testing of hardmetals
2026-09
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
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
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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
...