SE545894C2

SE545894C2 - Method for manufacturing an article comprising cemented carbide and an inserted object

Info

Publication number: SE545894C2
Application number: SE2130173A
Authority: SE
Inventors: Magnus Boström; Mikael Amnebrink
Original assignee: Sandvik Machining Solutions Ab
Priority date: 2021-06-22
Filing date: 2021-06-22
Publication date: 2024-03-05
Also published as: WO2022268845A1; SE2130173A1

Abstract

Disclosed is a method for manufacturing an article (100). The method comprises assembling (202) a green body comprising cemented carbide, the green body further comprising at least one recess. The method further comprises inserting (206) an object (120) comprising a material with a melting point above the sintering temperature into the green body, wherein the material exhibits less shrinkage than the cemented carbide when subjected to the sintering conditions. The method further comprises sintering (208) the green body comprising the inserted object (120), thus obtaining a manufactured article (100).

Description

|\/IETHOD FOR IVIANUFACTURING AN ARTICLE CONIPRISING CEI\/IENTED CARBIDE AND AN INSERTED OBJECT Technical field

[0001] The present disclosure relates generally to methods and systems for manufacturing an article, particularly for additively manufacturing an article comprising cemented carbide and a material with a melting point above a sintering tempefatU FG.

Background

[0002] Additive manufacturing, also known as 3D printing, generally involves manufacturing, or printing, one layer at a time using specialized systems. ln particular, a layer of powder material may be deposited in a powder bed system of a build chamber and bonded with another layer of the same or of a different material. Additive manufacturing may be used to manufacture articles from computer-aided design models using techniques such as binder jetting.

[0003] After the additive manufacturing steps have been performed and the powder composition has been shaped and bonded together, a green body is obtained. The green body is then subjected to sintering, in which heat and/or pressure is applied to the green body. During the sintering process, powder particles are bonded together which results in densification, and may also entail shrinking and/or deformation, which can negatively impact the resulting article.

[0004] Depending on the area of use, additively manufactured articles require different strengths. For certain areas of use, such as nozzles, it is important that the article has a high resistance to wear, which can be difficult to achieve with traditional additive manufacturing methods.

[0005] Consequently, there exists a need for improvement when it comes to additively manufacturing articles with high strength and resistance to wear.

Summary

[0006] lt is an object of the invention to address at least some of the problems and issues outlined above. An object of embodiments of the invention is to achieve an article wherein part of the article has a higher resistance to wear, and/or comprises a geometry which has stricter requirements for dimensional tolerances than the rest of the article.

[0007] According to one aspect, a method for manufacturing an article is provided. The method comprises assembling a green body comprising cemented » ~ i \ .~ .~\\ ~ -x ;-\ 33 p; p; :w -\ .N w .\ .~.-\~ ->\ ~»^ : n .-\ :N 33 .~\~ .N \-\ .N w «~\ ~^ “ \ vi = švsšv: :de W: :AS w xšp-š :xx e: Qccc; m3 bolts-l carbide .=-= methodfurthercomprises inserting an object comprising a material with a melting point above the sintering temperature into the green body, wherein the material exhibits less shrinkage than the cemented carbide when subjected to the sintering conditions. The method further comprises sintering the green body comprising the inserted object, thus obtaining a manufactured article.

[0008] According to another aspect, an article is provided. The article comprises a first part comprising cemented carbidem an object inserted into the first part, the object comprising a material with a melting point above the sintering temperature into the green body, wherein the material exhibits less shrinkage than the cemented carbide when subjected to sintering conditions_\\g;=^~* . . ~ w . - _ ~ . ; -. . » ~ w. . wa w n s .w - w .-\-\ .-\ v» wß; .Mm . .w _ . .vw N ,-\ vw “NN .-\ .\~ ,-\ w .N . .«\.----\ -\. . w -\»-.-\--~ .nä m, \ \\\_.«_\». m, ~»~\»_. ~ ~wuä~t . \~. * ._~ U-...w .u __~\. ~ «_\~ \ ~~\:__*\ »»:__~\_.~~~ w .~~\..- a :Cwà \.~\.~\..-.~ ~ =~ mA: :lxihšxešxit \..-\.~ »han IM m ~ i :\.~:.l lvL: mm.- \.i\..-\ï\.~! mawà-.e i ms: \.-=: s. _

[0009] Further possible features and benefits of this solution will become apparent from the detailed description below.

Brief description of drawinqs

[00010] The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

[00011] Fig. 1 shows an exploded sectional view of an article according to an embodiment.

[OOO12] Fig. 2 shows a sectional view of an article according to an embodiment. [OOO13] Fig. 3 shows a sectional view of an article according to an embodiment.

[OOO14] Fig. 4 schematically shows steps of a method according to an embodiment.

Detailed description [OOO15] Briefly described, the present solution relates to a method for manufacturing an article comprising both cemented carbide and another material with a melting temperature higher than a sintering temperature which the article is subjected to during manufacture. The method comprises assembling a green body comprising cemented carbide . . . .- .- .. v .- . .. . _. . . . . à. .. ._ W... a.. _. .. ..:.. at. ..-. _...... W s... a. ..,.,.\. _.. .à .à .à.\ »m ~ :à.\:~.\ .à : .à .à u. ..à .à .à Mà. à .à .à à_.\ .\à . . .à .à .à H .à .à Nà tu.- :11 l\.=x,.\_.~ sei: :'\.= Lsto; Raw: :KS d Ek, :..~“\.=\-'\='\.=\..-E í.L.-“\.É\.VE.E :\.-: :AE šL: 3.: :äfi : :..~::. ~\~' åxå: :šL-E š= :KE k? åk» 1.:; »ac-å = then inserting an object comprising another material having a melting point above the sintering temperature of the green body--; into the green body, wherein the material exhibits less shrinkage than the cemented carbide when subjected to the sintering conditions. The method further comprises sintering the green body comprising the inserted object.

[00016] An insight underlying the present disclosure is that by inserting an object comprising a material into a green body comprising cemented carbide, wherein the material has different material properties in the form of a melting point above a sintering temperature and exhibiting less shrinkage than the cemented carbide when subjected to the sintering conditions, and then sintering the green body comprising the inserted material, an article may be achieved wherein part of the article has a higher resistance to wear, while still having a sufficiently strong bond between the cemented carbide and the inserted object such that the interface does not break before the inserted object does.

[OOO17] A reason for only having part of the finished article, i.e. the inserted object, having different material properties than the rest of the article is that the insert material may be a material which would not be suitable or possible to manufacture into the desired shape. For example, the material of the inserted object may have a higher hardness but also be more brittle than the rest of the article. When using traditional methods, it is difficult to achieve bond between the cemented carbide and the stronger material which is strong enough to not break before the stronger material itself breaks. However, when inserting an object, preferably which is relatively inert at the sintering temperature, and at least with a melting point above the sintering temperature, into a cemented carbide green body and then sintering the green body comprising the object, a strong bond is achieved between the cemented carbide and the inserted object. This is partly due to the cemented carbide exhibiting a larger shrinkage when subjected to the sintering temperature than the material of the object. ln some embodiments, it may further be due to that a new phase is formed between the cemented carbide and the object during the sintering, which further strengthens the bond therebetween.

[OOO18] The method is especially suitable for applications in which a relatively small part of the finished article is subjected to large amounts of wear, particularly the part comprising the inserted object comprising the material with different material properties.

[OOO19] The material of the inserted object should exhibit less shrinkage than the cemented carbide when subjected to the sintering temperature. The material should further have a melting point above the sintering temperature used for sintering the cemented carbide green body, wherein the term melting point is used to denote the temperature in which the whole or at least a majority of the material becomes liquid. ln such embodiments, suitable materials includes ceramics such as alumina, tungsten carbide and zirconium oxide. Thus, in some embodiments, the inserted object comprises a ceramic.

[OOO20] The temperature in which the whole material becomes liquid is commonly referred to as the liquidus temperature, and the temperature in which a material is completely solid is commonly referred to as the solidus temperature. The temperature used during sintering should always be lower than the liquidus temperature of both the cemented carbide and the material of the inserted object.

[00021] ln some embodiments, the temperature used during the sintering may be higher than the solidus temperature of the cemented carbide, but lower than the solidus temperature of the material of the inserted object.

[00022] ln some embodiments, the temperature used during sintering may be lower than the solidus temperature of the cemented carbide. ln some embodiments, the temperature used during sintering may be higher than the solidus temperature of both the cemented carbide and the material of the inserted object.

[00023] The method is further suitable for applications in which the inserted object comprises dimensional tolerances which are difficult or impossible to achieve using only additive manufacturing, particularly wherein the parts with tolerances which are difficult to achieve are comprised on an internal side of the inserted object. An example of a geometry comprising such dimensional tolerances can be an internal thread of the inserted object. Such geometries may be difficult to achieve with ceramics, and thus, in such applications, suitable materials may include metals such as tungsten or molybdenum, which may have been formed by machining. ln some embodiments, the material of the inserted object may also comprise cemented carbide, but which has been formed by pressing.

[00024] Looking now at Figs. 1 and 2, an embodiment of an article manufactured using methods as disclosed herein will now be described.

[00025] Fig. 1 shows an exploded sectional view of an article 100, comprising a first part 105 comprising recess 110 into which an object 120 can be inserted. The first part 105 of the article 100 may in some embodiments comprise a flow channel 100, and the object 120 may also comprise a flow channel 125. The first part 105 of the article 100 comprises cemented carbide. The object 120 comprises a material with a melting point above the sintering temperature used during the manufacturing process, and the material exhibits less shrinkage than the cemented carbide when subjected to the sintering conditions.

[00026] Fig. 2 shows a sectional view of the article 100, wherein the object 120 is inserted into the first part 105 of the article. The outer area of the object 120 is in contact with the first part 105 of the article 100, and in some embodiments there may be a new phase formed between the cemented carbide and the object, wherein such a new phase is formed during the sintering process.

[00027] The article 100 may for example be a nozzle comprising a flow channel 115 and the object 120 may be a mouth for the nozzle comprising a flow channel 125, wherein a liquid is intended to flow through the flow channels of the article, from the first flow channel 115 into the second flow channel

[00028] A nozzle is one example of an article in which one part, in this case the mouth, requires a higher resistance to wear than the rest of the article, due to it being subjected to much stronger wear than the rest of the article, and thus tends to break or become worn out much quicker. As previously described, by using methods as disclosed herein, a sufficiently strong bond may be achieved between the object and the cemented carbide, such that the bond between them does not break before the object breaks or is worn out.

[00029] lt is important that the inserted object comprises a material having a higher melting temperature than the sintering temperature used during manufacturing. ln some embodiments, the inserted object comprises a material with less shrinkage than the cemented carbide during the sintering. ln some embodiments, the inserted object 120 comprises a material which is substantially inert at the sintering temperature.

[00030] Fig. 3 shows a sectional view of an embodiment wherein the object 120 protrudes from the first part 105 of the article

[00031] Looking now at Fig. 4, steps of a method according to an embodiment will now be described in more detail.

[00032] The method comprises assembling 202 a green body, which may correspond to the first part 105 of Figs. 1-3, comprising cemented carbide powder, wherein the green body further comprises a recess. The assembling step 202 is traditional additive manufacturing step, wherein powder is dispensed to a bed and then bonded together. The term “bonded” in this context entails that the powder particles are made to adhere to each other in any way. ln the case of binder jetting, this may entai| that dispensing binder to the powder is considered to bond the powder together. Further, sintering the powder with the dispensed binder may further bond the powder particles together. Thus, the powder is considered to be bonded together both after binder has been dispensed, and after sintering has been performed.

[00033] The method further comprises inserting 206 a material with a me|ting point above the sintering temperature into the recess of the green body.

[00034] The method further comprises sintering 208 the green body comprising the inserted object. During the sintering step 208 the cemented carbide will shrink around the inserted object, and thus achieve something similar to a shrink fit.

[00035] ln some embodiments, assembling 202 the green body comprises additively manufacturing the green body. ln some embodiments, assembling the green body comprises additively manufacturing the green body using binder jetting.

[00036] ln embodiments, the thickness of each layer of powder in the additive manufacturing steps is 40 - 250 microns, preferably approximately 50 microns.

[00037] ln some embodiments, the range of the particle size of the powder is 1 - microns.

[00038] ln some embodiments, the density of the powder prior to any sintering, including pre-sintering, is 30 - 60% of full density, preferably around 50%.

[00039] ln some embodiments, the sintering 208 is performed such that there is a new phase formed between the inserted object and the cemented carbide. ln examples wherein the material of the object is alumina, such sintering 208 may comprise sintering with a temperature of approximately 1425° C in a vacuum for approximately 2 hours.

[00040] ln some embodiments, the sintering 208 is performed such that the cemented carbide is sintered to at least 95% of full density, wherein full density denotes a state in which the cemented carbide is without any pores. ln some embodiments, the sintering 208 is performed such that the cemented carbide is sintered to substantially full density.

[00041] ln some embodiments, the inserting 206 comprises inserting the object such that substantially all of the outer surface of the object is in contact with the cemented carbide after the sintering has been performed. Since the cemented carbide will shrink to at least some extent during the sintering, there may be some gaps between the object and the cemented carbide when the object is inserted into the green body, but which gaps will disappear during the sintering as the cemented carbide shrinks around the object. ln some embodiments, the inserting 206 comprises inserting the object such that at least 50% of the outer surface area of the object is in contact with the cemented carbide after sintering.

[00042] ln some embodiments, part of the inserted object is inside of the rest of the article, while a part of the inserted object protrudes from the rest of the article. ln such embodiments, the inserting 206 may comprise inserting the object such that substantially all of the matching surfaces of the object is in contact with the cemented carbide after the sintering has been performed. Such an embodiment is shown in Fig. 3, which shows a sectional view of such an embodiment.

[00043] ::~'::^:*;~“: ~^::*;^;?^:::fi?i:*:w~*::°wf::,}j«ëhe method further comprises partially sintering 204 the green body, prior to the inserting 206, such that the cemented carbide is sintered to less than full density. ln some embodiments, partially sintering 204 comprises sintering the cemented carbide to between 60 and 90% of full density. ln some embodiments, partially sintering 206 comprises sintering the cemented carbide to approximately 70% of full density.

[00044] ln some embodiments, the method further comprises adding 207 an adhesive in the interface between the object and the cemented carbide. By adding an adhesive, an even stronger bond may sometimes be achieved between the object and the cemented carbide. ln some embodiments, the adhesive comprises a material which reacts with at least one of the cemented carbide and the material of the object. ln such embodiments, the adhesive may help achieve that a new phase is formed between the cemented carbide and the object, in case a new phase is not formed by only having the object and the cemented carbide react.

[00045] ln some embodiments, the object and the green body both comprise a duct, and the inserting 206 comprises inserting the object such that the ducts are substantially aligned. This may for example be the case when the article is a nozzle and the object is a mouth of the nozzle.

[00046] ln some embodiments, the inserted object comprises alumina.

[OOO47] Although the description above contains a plurality of specificities, these should not be construed as limiting the scope of the concept described herein but as merely providing illustrations of some exemplifying embodiments of the described concept. lt will be appreciated that the scope of the presently described concept fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the presently described concept is accordingly not to be limited. Reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the above- described embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed hereby. l\/loreover, it is not necessary for an apparatus or method to address each and every problem sought to be solved by the presently described concept, for it to be encompassed hereby. ln the exemplary figures, a broken line generally signifies that the feature within the broken line is optional.

Claims

1. A method for manufacturing an article (100), comprising: assembling (202) a green body comprising cemented carbide by additively manufacturing it by dispensing powder to a bed and bonding the powder together, the green body further comprising at least one recess (110); partially sintering (204) the assembled green body; inserting (206) an object (120) comprising a material with a melting point above the sintering temperature into the green body, wherein the material exhibits less shrinkage than the cemented carbide when subjected to the sintering conditions; and sintering (208) the green body comprising the inserted object (120), thus obtaining a manufactured article (100).

2. The method according to any of the previous claims, wherein sintering (208) the article comprises sintering the article such that a new phase is formed in the interface between the object and the cemented carbide.

3. The method according to any of the previous claims, wherein sintering (208) the article comprises sintering the cemented carbide to at least 95% of full density.

4. The method according to any one of the previous claims, wherein inserting (206) the object comprises inserting the object such that substantially all of the outer surface area of the object facing the green body is in contact with the cemented carbide after the sintering has been performed.

5. The method according to any one of the previous claims, wherein the method further comprises: adding (207) an adhesive in the interface between the object and the green body, prior to the step of sintering the article.

6. The method according to claim 6, wherein the adhesive comprises a material which reacts with at least one of the cemented carbide and the material of the object.

7. The method according to any one of the previous claims, wherein partially sintering (204) the assembled powder comprises sintering it to approximately 80% of full density.

8. The method according to any of the previous claims, wherein the object and the cemented carbide article both comprise a duct, and wherein the object is positioned such that the ducts are substantially aligned.

9. The method according to any one of the previous claims, wherein the material is a ceramic.

10. The method according to any one of claims 1-8, wherein the material is a metal.

11. An article (100), comprising: a first part (105) comprising cemented carbide; and an object (120) inserted into the first part (105), the object (120) comprising a material with a melting point above the sintering temperature into the green body, wherein the material exhibits less shrinkage than the cemented carbide when subjected to sintering conditions, wherein the article has been manufactured using the method according to any one of claims 1-10.