INTERNATIONAL STANDARD ISO 4499-3 First edition 2016-02-15 Hardmetals — Metallographic determination of microstructure — Part 3: Measurement of microstructural features in Ti (C, N) and WC/cubic carbide based hardmetals Métaux-durs — Détermination métallographique de la microstructure — Partie 3: Mesure des caractéristiques des microstructures des métauxdurs base de carbures Ti (C, N) et WC/cubiques Reference number ISO 4499-3:2016(E) © ISO 2016 ISO 4499-3:2016(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2016, Published in Switzerland All rights reserved Unless otherwise specified, no part o f this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2016 – All rights reserved ISO 4499-3:2016(E) Contents Page Foreword iv Introduction v Scope Normative references Terms and definitions Symbols and units Principle Apparatus Calibration Preparation of test samples 8.1 8.2 8.3 Metallographic preparation Ti(C, N) based hardmetals – cermets WC/Cubic carbide based hardmetals 9.1 Sampling of images of structure 20 9.1.1 General 20 9.1.2 Representative selection 20 9.1.3 Determination o f homogeneity o f hard phase sizes 20 9.1.4 Inhomogeneous materials 21 Phase size measurement 21 9.2.1 General 21 9.2.2 Phase measurement by intercepts 21 Procedure for characterisation of structures 20 9.2 10 11 Uncertainty of measurement 23 Test report 23 Bibliography 25 © ISO 2016 – All rights reserved iii ISO 4499-3:2016(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f preparing International Standards is normally carried out through ISO technical committees Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso.org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) Any trade name used in this document is in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the meaning o f ISO specific terms and expressions related to formity assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary in formation The committee responsible for this document is ISO/TC 119, Powder metallurgy, Subcommittee SC 4, Sampling and testing methods for hardmetals ISO 4499 consists of the following parts, under the general title Hardmetals — Metallographic determination of microstructure: — Part 1: Photomicrographs and description — Part 2: Measurement of WC grain size — Part 3: Measurement of microstructural features in Ti(C,N) and WC/cubic carbide based hardmetals — Part 4: Characterisation of porosity, carbon defects and eta-phase content iv © ISO 2016 – All rights reserved ISO 4499-3:2016(E) Introduction T h i s p a r t o f I S O 49 e s s enti a l ly covers the — fol lowi ng topic s: materia l s typ e s and ph as e s to b e me a s ure d i nclud i ng the fol lowi ng: — Ti(C, N) cermets; — WC/Cubic carbide hardmetals; — preparation methods to highlight differences between conventional WC/Co hardmetals and materials containing cubic phases; — l i ne a r ana lys i s te ch n ique s to acqui re s u fficient s tati s tic a l ly me an i ng fu l data for phas e qua nti fic ation; — a na lys i s me tho d to c a lc u late repre s entative average va lue s; — rep or ti ng to comply with mo dern qua l ity re qu i rements © ISO 2016 – All rights reserved v INTERNATIONAL STANDARD ISO 4499-3:2016(E) Hardmetals — Metallographic determination of microstructure — Part 3: Measurement of microstructural features in Ti (C, N) and WC/cubic carbide based hardmetals Scope This part of ISO 4499 gives guidelines for the measurement of microstructural features in Ti(C,N) b a s e d rd me ta l s a nd WC/C o h ard me ta l s th at contai n add itiona l c ubic ca rbide s by me ta l lo graph ic te ch n ique s on ly u s i ng op tic a l or ele c tron m icro s cop y I t i s i ntende d for s i ntere d hard me ta l s (a l s o c a l le d cemente d c arbide s or cerme ts) conta i ni ng pri ma ri ly i norgan ic c arbide s and nitride s a s the hard pha s e I t i s a l s o i ntende d for me as u ri ng the pha s e s i z e and d i s tribution b y the l i ne ar i ntercep t te ch n ique Normative references T he fol lowi ng i nd i s p en s able c uments , i n whole or i n p ar t, a re normatively re ference d i n th i s c u ment and a re for its appl ic ation For date d re ference s , on ly the e d ition cite d appl ie s For u ndate d re ference s , the late s t e d ition o f the re ference d c u ment (i nclud i ng any amend ments) appl ie s ISO 4499–1:2008, Hardmetals — Metallographic determination of microstructure — Part 1: Photomicrographs and description ISO 4499–2:2008, Hardmetals — Metallographic determination ofmicrostructure — Part 2: Measurement of WC grain size Terms and definitions For the pu r p o s e s o f th i s c ument, the fol lowi ng term s and defi n ition s apply 3.1 nano with c arb on itride or c ubic c arbide pha s e s i z e < , µm, re s p e c tively N o te to entr y: M e a s u re d b y the me a n-l i ne a r-i ntercep t me tho d de s c r ib e d i n I S O 49 -2 3.2 ultrafine with c arb on itride or c ubic c arbide pha s e s i z e , µm to , µm, re s p e c tively N o te to entr y: M e a s u re d b y the me a n-l i ne a r-i ntercep t me tho d de s c r ib e d i n I S O 49 -2 3.3 submicron with c arb on itride or c ubic c arbide pha s e s i z e , µm to , µm, re s p e c tively N o te to entr y: M e a s u re d b y the me a n-l i ne a r-i ntercep t me tho d de s c r ib e d i n I S O 49 -2 © ISO 2016 – All rights reserved ISO 4499-3:2016(E) 3.4 fine with c a rb onitride or c ubic c a rbide ph as e s i ze , µm to , µm, re s p e c tively N o te to entr y: M e a s u re d b y the me a n-l i ne a r-i ntercep t me tho d de s c rib e d i n I S O 49 -2 3.5 medium with c a rb onitride or c ubic c a rbide ph as e s i ze , µm to , µm, re s p e c tively N o te to entr y: M e a s u re d b y the me a n-l i ne a r-i ntercep t me tho d de s c rib e d i n I S O 49 -2 3.6 coarse with c a rb onitride or c ubic c a rbide ph as e s i ze , µm to , µm, re s p e c tively N o te to entr y: M e a s u re d b y the me a n-l i ne a r-i ntercep t me tho d de s c rib e d i n I S O 49 -2 3.7 extra coarse with c a rb onitride or c ubic c a rbide ph as e s i ze > , µm, re s p e c tively N o te to entr y: M e a s u re d b y the me a n-l i ne a r-i ntercep t me tho d de s c rib e d i n I S O 49 -2 3.8 Ti(C, N) cermets TiC N-b as e d cerme t conta i n s to weight % o f a bi nder pha s e mai n ly comp o s e d o f C o a nd/or Ni, but may a l s o i nclude M o N o te to entr y: T he b a l a nce b ei n g s ub s ta nti a l l y a h a rd p h a s e a nd a few m i nor i mp u r itie s N o te to entr y: T he h a rd ph a s e i s m a i n l y co mp o s e d o f tita n iu m c a rb ide , n itr ide a nd/or c a rb o n itr ide , b ut m ay also include carbonitrides of (Ti,Ta), (Ti,W) or (Ti,Ta, W) N o te to entr y: T he s e m ater ia l s typic a l l y co nta i n h a rd p h a s e s th at c a n h ave gra i n s with a core/r i m s tr uc tu re 3.9 WC/Cubic carbide hardmetals hexagonal WC-based hardmetals containing substantial amounts of a carbide having a cubic lattice, such as, for example TiC or TaC, and which can contain W in solid solution N o te to entr y: T he s e m ater ia l s typic a l l y co nta i n h a rd p h a s e s th at m ay h ave gra i n s with a co re/ri m s tr uc tu re N o te to entr y: S e e Table 3.10 phase region single constituent of the hardmetal like WC, cubic carbide or binder Symbols and units area, in square millimetres (mm ) A ECD E qu iva lent C i rcle D i ame ter o f a s p e ci fie d pha s e, i n m icrome tre s (μm) L to ta l l i ne leng th i n a s p e ci fie d phas e, i n m i l l i me tre s (m m) li me a s u re d leng th o f i nd ividua l i ntercep ts i n a s p e ci fie d ph as e, i n m ic rome tre s (µm) ∑ l i sum of the measured length of each individual intercept © ISO 2016 – All rights reserved ISO 4499-3:2016(E) lx arithmetic mean linear intercept in phase x, in micrometres (µm) N number o f grain boundaries traversed in or between specified phases n number of WC, carbonitride or cubic carbide grains intercepted m magnification m max maximum magnification m minimum magnification Principle This part of ISO 4499 addresses the issue of good practice for the measurement of a mean value for the hard phase and binder phase size in hardmetals other than straight WC/Co It recommends the use of a linear intercept technique for obtaining data on feature sizes The measurements are to be made using good practice for the preparation of suitable microstructures for examination outlined in ISO 4499-1 Methods of metallographic preparation and etching techniques are as important as the phase size measurement method (see also ASTM B 657, ASTM B 665, Reference [1] and Reference [2]) Basic methods are described in ISO 4499-1 Further relevant information is given in Clause The principal types o f hardmetal considered are those that contain cubic carbides as well as WC and those that are based on TiC or Ti(C,N) [3][4][5] A cubic carbide phase is defined as a carbide having a cubic lattice, such as, for example, TiC or TaC, and which usually also contains W in solid solution a fter sintering These materials typically contain hard phases that have grains with a core/rim structure Guidelines to measure these internal details are included in ISO 4499–2:2008, Annex A The most direct way to measure the phase size is to polish and etch a cross-section o f the microstructure and then to use quantitative metallographic techniques to measure a mean value for the feature size, either by area counting or by linear intercept techniques The following are three ways by which the mean size by number o f the various phases can be defined: — by length (o f a line across a 2D section o f a phase); — by area (o f 2D sections o f phase regions); — by volume (o f individual phase regions) A number average is obtained by counting each measurement o f the parameter o f interest (length, area or volume) and dividing the total value o f the parameter (length, area or volume) by the number o f this parameter counted The values for phase size most used to date have been based on a length parameter This can be obtained in the following several ways, for example: — by parallel lines or circles as described in ASTM E112; — by linear intercept, called the Heyn method, from a straight line drawn across the structure; — by equivalent circle diameter (see ISO 4499-2), this is obtained by measuring hard phase grain areas and then taking the diameter of a circle of equivalent area Apparatus 6.1 Metallographic optical microscope , or other suitable equipment permitting observations and measurements on a screen up to the required magnification © ISO 2016 – All rights reserved ISO 4499-3:2016(E) Scanning electron microscope , permitting observations and measurements of features too small to be resolved with an optical microscope 6.2 6.3 Equipment for preparation of test-piece sections Phase size measurements are obtained from images of the microstructure ISO 4499-1, ASTM B 657 and ASTM B 665 should be consulted for best practice in the preparation of surfaces for imaging Structural images are usually generated by either optical microscopy or Scanning Electron Microscopy (SEM) For accurate measurements, it is better to use scanning electron microscopic images Even in coarse grained materials, the imaged surface cuts through a substantial number of the scanning electron microscope corners o f grains giving a proportion o f small intercepts that can only be measured accurately using the Measurements o f intercept lengths from the acquired images can be obtained manually or semiautomatically using image analysis Automatic image analysis can be used in some circumstances when the images are fairly coarse and good contrast can be obtained but for many materials, especially those with very fine grain sizes, good images are di fficult to acquire and are generally not amenable to automatic analysis For the ultrafine and nano structural materials, good images are particularly di fficult to acquire using conventional scanning electron microscopes with tungsten filament electron sources It is recommended for these materials that a field emission SEM is used These systems give significantly higher resolution images, su fficient to measure materials with mean intercept sizes o f about 0,1 µm to 0,2 µm For materials with ever smaller grain sizes, it can be necessary to use Transmission Electron Microscopy (TEM) However, the problems o f sampling and specimen preparation are particularly severe Careful specimen preparation for good images is vital for these materials and often a combination of etching methods is helpful (see ISO 4499-1) Calibration To give reliable quantitative measurements, images shall be calibrated against a stage micrometer or scale traceable to a National Reference Standard For images obtained from an optical microscope, an image of the calibration graticule shall also be obtained using the same objectives (and internal magnification step changers or zoom position) and illuminating technique The microscope shall be set up for Köhler illumination to obtain the maximum resolution (see Reference [6]) For images obtained from a scanning electron microscope, images of the graticule should be obtained under the same conditions (accelerating kV, working distance, illumination aperture) as those used for the hardmetal Preparation of test samples 8.1 Metallographic preparation The basic steps for good metallographic sections of hard materials are given in detail in ISO 4499-1:2008, stage for these materials, which was performed using colloidal suspension of silica (at 40 nm particle size) on a napless silk cloth Appropriate etching methods for cermets and hardmetals containing cubic carbides are outlined in 8.2 and 8.3 , respectively 6.1 for sectioning, mounting, grinding, lapping, polishing and cleaning, except for the final polishing 8.2 Ti(C, N) based hardmetals – cermets The preparation o f the test samples is recommended to be according to ISO 4499-1:2008, 6.2.1 by using etching technique The conditions o f etching in mixture A should be changed to approximately 20 °C © ISO 2016 – All rights reserved ISO 4499-3 :2 016(E) Figure 10 — Material 3, optical micrograph, original magnification ×1 600 Figure 11 — Material 4, optical micrograph, original magnification ×1 000 12 © ISO 2016 – All rights reserved ISO 4499-3 : 016(E) Figure 12 — Material 4, optical micrograph, original magnification ×1 600 Figure 13 — Material 1, SEM micrograph, original magnification ì20 000 â ISO 2016 All rights reserved 13 ISO 4499-3 :2 016(E) F 14 i g u r e — M a t e r i a l , S E M m i c r o g r a p h , o r i g i n a l m a g n i f i c a t i o n × 0 © ISO 2016 – All rights reserved ISO 4499-3 : 016(E) F i g u r e — © ISO 2016 – All rights reserved M a t e r i a l , S E M m i c r o g r a p h , o r i g i n a l m a g n i f i c a t i o n × 0 15 ISO 4499-3 :2 016(E) F 16 i g u r e — M a t e r i a l , S E M m i c r o g r a p h , o r i g i n a l m a g n i f i c a t i o n × 0 © ISO 2016 – All rights reserved ISO 4499-3 : 016(E) Figure 17 — Material 3, SEM micrograph, original magnification ì15 000 â ISO 2016 All rights reserved 17 ISO 4499-3 :2 016(E) Figure 18 — Material 3, SEM micrograph, original magnification ì20 000 18 â ISO 2016 – All rights reserved ISO 4499-3 : 016(E) F i g u r e — M © ISO 2016 – All rights reserved a t e r i a l , S E M m i c r o g r a p h , o r i g i n a l m a g n i f i c a t i o n × 0 19 ISO 4499-3:2016(E) F i g u r e — M a t e r i a l , S E M m i c r o g r a p h , o r i g i n a l m a g n i f i c a t i o n × 0 Procedure for characterisation of structures 9.1 Sampling of images of structure 9.1.1 General S ampl i ng for m ic ro s tr uc tura l pu rp o s es s to b e c are fu l ly s idere d dep end i ng on the re as on undertaking the measurements Attention should be paid to the explanation in 9.1.2 to 9.1.4 9.1.2 for Representative selection T he i mage s cho s en for ana lys i s s hou ld b e repre s entative o f the whole s e c tion a nd shou ld b e ob ta i ne d by ndom p o s ition i ng T he nu mb er o f i mage s to b e prep a re d i s re com mende d to b e at le as t fou r, wh ich ca n b e i nten s ively a na lys e d s o that, i n to ta l , at le a s t 0 releva nt ph as e region s i s me as u re d 9.1.3 Determination of homogeneity of hard phase sizes I n th i s c as e, a s ys tematic s e t o f i mage s from defi ne d lo cation s with i n the s e c tione d are to b e ob ta i ne d and i nten s ively ana lys e d s o that at le a s t 0 pha s e region s a re me as u re d a l low for from e ach lo c ation T h i s wi l l e xa mple, trend s i n pha s e s i ze gre ater than the l i kely error o f me a s u rement at e ach p o s ition (fractional error is proportional to N where N is the number of phase regions in each location) to be determined 20 © ISO 2016 – All rights reserved ISO 4499-3:2016(E) 9.1.4 Inhomogeneous materials In cases where the microstructure is inhomogeneous from one field o f view to the next, it is good practice to increase the number o f images evaluated, but to evaluate them less intensively, while still achieving a total feature count of >200 The magnification o f the image obtained should be such that there are between 10 and 20 phase regions across the field o f view permitting individual intercepts to be measured to better than 10 % accuracy This will usually allow three or four linear intercept lines to be drawn across the image without intercepting any individual phase regions more than once Most hardmetals have little or no anisotropy o f structure, so it is unimportant i f more or less parallel lines are used I f anisotropy is suspected, then it is better to orientate the lines randomly and permit their intersection Thus, from each image, about 50 linear phase size intercepts can be obtained 9.2 Phase size measurement 9.2.1 General It is recommended that the arithmetic mean linear intercept is used as the parameter to define phase size This is the simplest procedure to use and has the added advantage of providing data that can be used to quanti fy distribution width For a two, three or four phase material such as can be present in Ti(C,N) or mixed WC/cubic carbide hardmetals, the linear intercept technique is less straightforward because each phase has to be measured independently However, it can also provide in formation on phase size distribution A line is drawn across a calibrated image of the microstructure of a hardmetal sample Where this line intercepts a hard phase or region of binder, the length of the line ( ) is measured using a calibrated rule (where = 1, 2, 3,… for the st, nd, rd … th grain) It is advisable to count at least 100 lengths, preferably li i n n at least 200, in order to reduce the uncertainty in the mean value o f size (phase or grain) to below 10% The mean linear intercept phase or binder phase size is defined as given in Formula (1): dx = ∑ li n (1) Hardmetal phase sizes generally fall in the range 0,01 µm to 10 µm Because o f the uncertainties o f measurement, it is good practice to report the mean linear intercept size to one decimal place for values >1,0 µm and to two decimal places for values