CA2085246A1 - Process for applying a coating to a substrate, coating as well as plasma torch - Google Patents

Abstract

Abstract The invention relates to a process for the application of a coating on a substrate by means of a plasma torch, a correspondingly applied coating, as well as a plasma torch intended and suitable to implement the process. The coating consists of a matrix as effective layer and embedments of diamond particles for improving the matrix characteristics or of a matrix as binder material with therein embedded particles which then form the actual effective layer. Depending on the parameters selected during coating, primarily depending on the distance of the substrate from the plasma torch and on the addition of carbide producers to the plasma torch, it is possible to select various densities of diamond material, respectively matrix material in the coating.

Description

1~761 2~2ll6 P~CESS F0R APPLYING A COA~N~; T~ A ~ STR~TE, COA~ING AS wE.~L AS P~ O~

~he invention rela~ to a pro~es~ ~or applying a coa~lng on a substrat~ by means of a ~lasma tor~h, a ~orre~pondingly applied ~oating and a plasma tsrt:h intended and suitable ~o p~form tha process.

Coatings are app~ied ~or impro~ing the aharact~ristic~ o~
und~rlying mak~rials u~d ~or a ~ariety Or purposes~ one o~ t~e po~ibilities to apply a co~ting is the ~-aalled C~D-prooe~s, wh~rein one or two el2ments ~re ~eparated from the ~a~ phase an~
conden3e the instarlt they h~t tho subs~rate. With two el~ment~
it is a~ways the c~ o~ simpl~ aompound~ ~orm~d by ~ lln~ed reaotlon. As nn example ~or suoh a CVD-coating titan~ um carbide aan be mention~d, wh~raby the initial gases a~ met~an~ ~nd tltanium t~t~nchlorid~, th~ ~-3ult o~ ~h2 rea~tLorl bein~ tltanium ~a~bid-t and Hcl. HCl 15~ removed~

Anoth~r wa~ t~ apply coatings to a substrate ~s plasma 6praying, i.e. a thermal 9pray~ng w~e~sby tempe~atures up t~
20,000 ~ are produced in the plAsma torch, tn order to melt a ma~erial supplied as a powd~r or wire and to let it stxiXe the 187~1 2085~46 subs~r~e~ The plasm~ tor~he~ use~ ~or coating operate primarily on argon and ~o a 6mall exten~ on hydrogen or helium a~ a ~uel ga~ for ~he production o~ pla~ma, ~or which purpose a cathode an~
an anode inside the pl~sma korch a direct cur~nt is applied; the pl~sma can ~lso be produced through an electromagnetic hi~h-~re~u~nc~ alternating field. An example o~ a plasma torch is described for instance in the publication "Werkstatt und Betxieb", Year 1~84, Page 333. The supplied powde~ or wire can be alloya~ prior to introduction, -~o that the most complicated compound~, mixture~ and ~tructures can be sprayed onto the subs~ate, namely metals as well as cexamic mate~ials or mixtur~s thereof.

In many ca~e~, the coating applied by a plasma torah i~ a aomposite material, cons~sting ~ a matr~x as an ef~ec~ive la~r o~ th~ one hand and embedments ~ox impro~ing the mat~i~
chAr~ateristic~ on th2 othex hand. The ma~rix and the embedment~
d~e ~ed to th~ plasma tor~h in powder ~xm. Th~by thro~gh ~arlation~ in th~ p~wder addition it i$ E~cssible to reRch a grading dur~n~ th~ coating ~uildup, i.e. a modif~cation o~ ~he embedment density from a point directly on the su~strate ~ur~ace to a point of th~ ~ur~ace of the uture coating. A typical material ~or such a matrix is ~or instance a nick~l-c~romium alloy with embedded ch~omium carbides.

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187~1 2~24~
~ n re~en~ tim~a ~t beaame p~s~ble ~o ~pply pure diamond coating~ to a substrate, which i~ particularly important ~or the electranics indu~try. A aorresponding process is descrlbed in detail in the European Patent Application 90106785Ø ~he carbon required ~or the diamond partioles ~s ~upplied to the pla~ma ~et throu~h a ~rbon-con~ainin~ gas or liquid, where~y with the aid of hydrogen ~nd an inert gas it i~ insured that the carbon ~raction results in a deposition of diamond, respactively diamond-like mat~r~al an~ not ln ~ graphite deposition.
There~oxs this is a CVD-prooess whereby from a gaseous pha~e dlamond crystal~ ar~ separated through condensation.

The u~e~uln~g~ oP pur0 diamond coating~ resides primarily in th~ ~xa~llent electrlc in~ulation ch~ra~teris~ic~ and in th~
axcell~nt hRA~ conducti~i~y o~ th~ diamond. For the~e reason~, th~ dlamond creates exc~ nt canditions ~or heat sinks whereupon ~lec~ronic component~ sub~eotQd to hi~h thermal loads ar~
appl~Qd. 0~ cours~ th~ h~rdnes~ ~ diamond c~ating~ i~ al~o o~
inter~s~ lndus~xlal a~pliaat~on~, ~or instance a6 w~ar protection. ~owevor, a 6U~iC~ en~ adh2~ion to the sub~trate ma~erial i~ no~ easy to aohi~ve.

The Europcan Patent ~ppli~a~ion 90308570.2 describes a pro~ess and a device for applying di~mond layers accordlng to the CVD-technique. In order to improve the adhesion of the dlamond layer~, it is preceded by a bUildup 0~ one or more intermediate 2~8~2'~
layers, whq~eby parti~lar attenti~n is paid ~o the compati~illty o~ neighboring layers, particu~arly in order to manage ~ erent e~pansion ~oe~iaients of ~he substrate and the diamond material. The interme~ e layers are applied ~y the ~ame device app-lying the diamond layer.

Furthermore, coa~ings are dis~ose~ which con3ist o~
two-phase s~stems with ~h~ incorporation o~ carbon ~or diamond formation, which are al~o applied by the CVD-techni~ue. Thereby ~he one gaReous el~ments serv~s as a ~arbon carrier, while the oth~r ~aseous element encourage~ nu¢lei formation, whereby spe~ifiaally platinum, ni~kel, cobalt, iron, tungsten, silicon, molybdenum and tltanium are named. ThRse elements are intro~uced into the pla~ma as fine powder~ and vapo~ized. Based on th~
lndica~ed operation parameters o~ lO to 70 ampere and 50 to 150 volt ~e plasma can be settled in a corona discharge whlch i~ not wi~hin ~h~ rdnge o~ ~hermal equilibrium, which in fact matahes the disqlosure ln ~he European Pat~nt Application 9010~7~5, according to whlch the ~ep~r~tion o~ the diamond modi~iaatiQn ou~
o~ a ~arbon carrier has to t~ place during a "silent"
discharg~. ~her~ore, this is also a ma~er o~ a plasm~ in the l~wer energ~ l~vels.

It is ~h~ ob~eot o~ the invention to propose a novel t~chniqu~ ~or tha application o~ a ~oatin~, a nov~l coating a~
well a~ a plasma torch to bs used ~or implementing thia techniqu~, so that a sprayed-on ~o~ting can be ~c~ieved, who~e 2~$~2~6 charaak~istlcs can be very easily vari~d within a spectrum ranging ~rom ~he almo~t pure diamond coa~ ng wl~h a matrix a~ a ~inder to the matrlx ~3 an ef~e~tive layer with diamo~d embedment~ ~r the improvement of the Characterlstic# o~ th~
~ffective laye~.

The respe~tive invention i6 defined in ~laims 1, 7 and 13, to which ~p~ci~ic reference is made her~.

qurpri~ingly it has be~n ~ound that even in a ~ery energy rich, thermally b~lanced plasma which predominates inside a plasma torch for ~hermal ~p~ying, a reactlon chain ~akes plac~
which al~o leads to a separation o~ diamond particle~, al~hou~h ~o ~ilent dlYcharge or corona disohar~e are present to m~ke nvalla~l~ the en~y r~lease, but a potential which, with with respe~t to the ~nergy content i~ higher by an exponent o~ one to ono and hal~. Obviou~ly also in thes~ ene~gy rich pla~as radicals ar~ Pormed as ~ result of the mole~ule di~sociation o~
th~ carbon carr~er, th~se radi~als being ex~remely r~aative.
This has a ~ a re~ult the ~a~ that at ~he end of the plasma flame basi~ally all radiaals wil~ ~orm new compounds, so tha~ the don~ity of the radicals at ~he end of the ~lame will approach 2~ro, but will be ~onsidera~l~ higher ~t a ~hor~er dista~ae ~rom th~ plasm~ torch nozzle. ~ ~or ~he deposition o~ ~iamond~ on a aubstrat~ e.q. methane ~C~4) is used, the radical~ are c~3 atoms and hydro~en a~oms, which obviously play ,:

187~1 2~52a~
~n impor~ant part in determining whether on impact on the substrat~ a carbon atom depo~i~s a~ a graphite modification or crystallize~ into a diamon~ modi~ication.

A ~urther factor which contribute~ to ~he detexmination oP
the modifioation resulting from ~he crys~allization is ths compo~ition o~ ~he powder used for ma~rix ~ormati~, i.e. the effective l~yer, respe~tively the pure binder material, whl~h can be a ~ommonl~ ~nown pla~ma spray substance. The addition of carbide producer~, such a~ titanium, chrom~um, ha~nlu~ or zlrconium leads to bonding into car~ides of the free carbon whic~
doe~ not go into the diamond syn~hesis. ~he carbon which does not go ln~o the diamond synthesi~ can in addition be dissolved, ~or ins~ance through the additio~ o~ ~oba.~. It has to be mentioned th~t th~ in~luence on the cr~stalliæ~tion o~ carbo~
~nto the diamond modificati~n is not exerted through a ga6eou~
phase o~ the vaporiz~d powder, but that the reaction taxes pla~
~ol~ly with t~e mel~ed powder.

T2~e ~nvention propo~ or the ~ir~t time to vary by choice the ratio between the diamond particles and the matrix, whereby one extreme is represent~d by an almost pure diamond layer with the matrix acting a~ a binder material and the other ~xtrem~ by a matr~x wlth a low peroe~tage o~ finely distributed diamond particles; this with All ~orm~ 0~ mixe~ and appli~ation instance~
in betwee~, wherein the diamond particles as well as the ma~rix oan b~ a direct u~eful ~omponent. It has been proven that 2Q~2~l~
pure di~mond ooating~ adh~re poorly to the ~ub~trate and o~er in them~el~ only an insu~fioien~ bonding, so tha~ under flynamic stre~s it is pra~ti~ally impos~i~le to pu* the diamond hardne~s to good u~e. There oro the inven~ion compr$6e~ solely diamond partiales emPedded in a matrix, whe~eby of ~ourse th~ bindl~g mater$al ~an bo in a very low proportion, as long a~ it i~ finely di~tributed.

When ~h~ production o~ a ~oating with a high diamond ~ontent and a low matrix content i~ intende~, then ~he substra~e has to be brought relativ31y close to the plasma toroh nozzle, ~ecause at ~hi~ point the radical d~n~ity i6 highest. The high radioal density insur~s then that the ~arbon atoms are depo~ited on ~he ~ubstrats a~ dlamond m~dification. ~hi~ deposition i~ agaln and again p~rm~ated by th~ matrix compon~nt~, w~ich ~ix them~lves ~irst to the sub3trate as an adhesL~ bas;e and al90 w~t th~
diamond par~icl~s on all side~. As a re~3ult o~ ~he alo~ene~ o~
tho ~ubstrat~ to the plasma ~orch nozzle,, th~ su~tra~es i~
lnten~ely hea~od, unlQss it i~ int~n~iv~:Ly aooled by an arrangemant in ~he rear, w~ich aan con~ir~t of ~old gas showers, spraylng, application o~ cooled plates or ~y a ~low passing direc~ly through the substrate, When the propo~tion o~ ~h~ ma~rix with~n th~ coatin~ has to be increas~d, the su~stra~ is brought to a zone with lower radi~a~ den~ity in the plasma torch flame, whe~sby then ~ : .

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18761 2 ~

increa~ingly carbid~ produaer~ hsve to be admlx~ to the matrixmateri~l in the initial Porm a3 powder. The carbide producers, e.g. titanium, chrom~um, ha~nium or ~irconium insure that th~
exce B car~on i8 not depo~ited as g~aphite, but fo~ms ~arbides wi~h th~ ~o-called carbide produ~ers, which in turn ha~e ~xcellen~ wear ~hara~teristics, this way contributin~ togeth~r with ~he dispersed diamond particles to the w2ar resi~tance o~
~he coa~ing. In individual aas~s it i~ possibl~ to s~lect th~
carbide produaer, whereby this selec~ion depends mainly on its compatibility with the matrix. ~lternately, besides th~
simultaneouQ diamond synthesis and spray coating, each process component can also be per~ormed in an alternate time sequence~
i.e. al~ernately be deposited as a ~oating of pur~ matrix mate~lal or of purq diamond as hard substana~.

For oparating the pl~sma tor~h pa~ticularly a direc~current elea~xic ar is used. Thereb~ the applic:ation spectrum o~ a sp~ay~d coat;ing according to t~e invention i~ drastiaally wid~ned. Fox th~ dwellin~ time of the individual aompon~n~s ~n~ide the plasma tor~h it oan ~o suitab~e to u~e a high-frequency alt~rnating field ~or the p~ductio~ o~ plasma, inste~d of th~ direct-aur~ent electric arc. A ~urther possibility to improve ths dwelllng time resides in providing ~he re~pective plasma torch with an axial ahannel for the supply o~
the carbon-con~a~ninq ~as or liquid , through whi~h these 2 ~
compon~nt~ ar~ ~ed t~ the center of the ~orch. Beside~ in .hi3 ca~e there i~ no danger Or ohann~l occlu~on, since ~he reaation wit~ th~ rest o~ the components ~art only af~r the c~annal 1 exite~. As ~ sido e~ec~, th~ ca~hode i~ there~y coolad a~ th~
~ame time.

The coat~nqs a~o~d~ng ~o the in~ntion are prefera~ly perfoxmed in a pres~ure rang~ below the a~mospheric p~essure.
HOWQVOr, it is ~150 possible to obtain satis~actory re~ults even above atmo~ph~r~c pr~ssure, whe~by the dlstances have already been e~plained befor~. In practi~e, distances o~ 6 to ~0 am are use~ be~wa~n th~ substrate in th~ nozzle o~ the plasma toroh. 0~
course a ~as sh~athing made of an inert gas oould ~e ~uitabls ~or th~ prot~ction o~ thQ appli~d ooating during its ~ormation and imm~di~tQly a~t~r itB fo~mation, a ~at ~nown ~e~ ~ and whieh aan be achiev~d b~ means o~ annular no2z,1es around th~ Laval nozzle o~ th~ pla$mR torch. For hi~her pressures up to ~ bar and ~vr undaratmospheria pr~s~ures of 50 mbar it is s~ unders~ood tha~ a chamb~r wi~h oontroll¢d inner pressur~ i~ re~uir~ ~or the æubstrate. The appl~cation range sp~ci~ically includes an application undex liguid, e.g. under water.

R~cen~ly the production of so-c~lled fuilerenes, a new modification Q~ carbon, ha~ been achiev~d, whereby ~ spheri~ally shap~d oluster o~ 6Q to 70 car~on atoms is availa~le. Thi~
modi~ication can of ~ourse also be used as an effec~ive layer o~
as an embe~men~ in a ma~ri~, wh~n ~orresponding ~haracteristics ar~ desired.

la7~l 20~2~`6 ~ sp~aial f~ature o~ the inventio~ con~i~t~ in the faat that the thermal pla~ma 6prayin~ can be aombined with the diamond synthesis, without 105ing the wide ~ariation range mad~ po~sible by plasma spraying regardin~ the ap~icable coatings. The parame~ers o~ operating a plasma torch with a direct-current electric arc lie thereby ~ithin the usual fxamework, at a voltage o~ approximately l~o V, which can reach up to 500 ~ in individual cases, a current intensity o$ up ~o 1000 A can be r&ached, wh~reby powder amounts up to 5 ~g/hour at 50 to 300 l/min of argon are oonsumed. The typical grain size ~r the suppiied/
optlona~ly prsalloyed powder lies ~ithin the rang~ o~ 5 to loo /um~

Coatlngs o~ alloys with oxidation stability, or all~ys wlt~
resistance to ho~ gases, or corrosion r~sistant alloys can ~e sprayed with diamond~ in order ~o improv~ their hardnes~
oha~aote~l~tic~, namely ~or instanoe M-Cx-Al-Y-alloys, whereln the lett~r M s~ands Eos tha ~lemen~s iron, o~bal~ ~nd~ox nlckel.
Wear and corrosion r~si6tant alloys, as well as pure hard alloy~ :
on an iron-cobalt- or nic~cal basis can also be sprayed with the admixture o$ diamon~s, in the same way as pure cobalt-hard mate~ial allc)ys c:ommerc:ially lcnown as stellite. E~ard nickel ~lloys containing ni~kel, chromium, boron and silicon, are use~
~or simil~r purpo~es. Fur~hermore, it is o~ course posslble ta spray hard metals on a tungsten ~arbide-cobalt b~sis, on a tungs~en-titaniu~ carbide/tantalum carbide-cobalt ~asis or o~ a niokel-ohromlum carbida ba is. Diamond modi~cations can al~o be ~dmixed to ~hese hard metals in order to improve their ~haraoteri~tics.

1876~

Th~ afoxemanticned sprayable coatings are named ~olely as examples in the ~i~ld o~ prote¢tion agains~ corro~ion and wea~.
Du~ to the v~ry high en~r~y during pl~sma spraying, o~ide c~ramio and nonox~ ceram~ ~aterl~ls ~ix~d wit~ moly~denum, also ~nown unde~ th~ name ce~met, can be ~prayed. Sprayable axe ~l~o all pure oxides and mixed oxi~e~, a~ well as mul~i~omponen~ oxide~, eaoh being mod~la~le according to the invention with the diamond material. ~60 ~ilicate known under the designation cordleri~
ha~e to be men~ioned her~.

Even in biocompa~ible ¢oatings,when phosphates, al~o known under the name o~ hydroxyl~apatite, axe ~pxa~ed, it can be u~eful in ~rtain case~ to introdu~e diamond embedments in various di~tributions and density, again in order to improve the wear ahara~eristi~. This applieo Rlso to the qpraying o~
lntermetallia phase~ o~ b~nary, ternar~ or even hl~h~r ~y~t~m~
e.g. on a ni~sl-Rluminum-, tltanium ha~is and more ~ the 3ame.
Finally, durln~ ~he spra~in~ o~ haavy metals ~n~ con~c~
ma~rial~ it can be advantageau~ in ~erta~n indlvidual cas~ to imbed wear-reduciny diamond hard material, which can ea~ily be done with th~ aid o~ the inven~ion.

The afor~mentioned examples chow what a wide application ran~e i5 o~fered by the~mal pl~sma spraying, whereby based on the invention it be~mes poss~bl~ ~or ~he ~irst time to bring dtamond 1~761 2 ~
embedm~nts, re~ea~ively almost pure diamond la~er~ i~ conn~ction wlth these m~trice~ i8 alway~ l~portan~ to Xeep su~iciently ~avorable paramete~s for ~h~ separation of diamond modifiaation ~ro~ carbon, which however i~ no problem within the ~ramewor~ of the pre~e~t invention.

Fur~her, an embodimen~ example o~ a plasma torch accordin~ to the inventi~n and ~or ~he implementation o~ the pro~ess o~ ~he invention is alosex des¢ribed as shown in the drawing: the ~ole ~iguxe of the drawing showss a aross slection through a schematically represen~d plasma torah aaaording to the invention ~or producing a ~oat~ng accordin~ to the ~nventi.on.

The illustrated pl~ma torah consist~ of a ~asic body 1, to whiall an anode 2 and a ¢athode 3, electr~ally insulated with xespect to ea~h othe~, are moun~ed. Between both eleatrode~
there is an elec~ric ara zone 4, wherein electric discharges take place, whiah are a preaondition for plasma ~ormation. Beca~se of th~ hiqh thermal load, the torc~ is ~ooled b~ a travereing flow with th2 aid of a coolin~ wate~ inlet 5 and a coolin~ water outlet 6, where~y at the same time the anode ~ and the c~thode 3 are also reached. via a sepa~ate fuel gas connection 7 ar~on or a mixture o~ ar~on and hydrQgen is upplied. At the ~rontal ~nd la7Bl 2~$~2~

oP anode 2 thflxe ia a powd~r ~let 8 ~or the supply ~ the matrix material, as well as o~ the materials o~ the embedments to ~he pl~sma flam~ ~2.

~ he ~a~ic body 1 a~ well a~ the cathode 3 are provided with an axial channel lo through whioh a ~arbon-containin~ ~a~, ~u¢h a~ methane or a ~ar~on-containin~ liquid such as alcohol i~
~n~roduaed in the r~action zone o~ the plasma to~h. Thi~
component conta~ns the oarbon ~rom whiah la~er the di~per~e~
diamond hard material will re6ult. Instead o~ pas~ing throug~
chann~l 10, ~hQ msthane can also be introduced in the plasma ~hrough thæ powder inje~t~on pipe, i.e. the powder inlet 8. All componen~s par~icipating in the coatlng deposition leave the plasma torch a~ 5pray jet 13 and strike a ~ubstrate 14, whereupon th~ ~oating 15 i9 ~ormed.

~ he plasma torch to~ether with the stlbstrate 1~ aan be accommodat~d ~n an unde~pre~uro ahamb~r, which i8 not clo~er sh~wn in the drawin~. This i~ continuou,31y kept at a preselec~d pressur~, ~or ins~ance at a pre~ure o~ 50 m~ar. Be~au9~ o~ the ~ontinuou ly ~lowing pl~sma this underpressure chamber has to be mai~a~ned at the same pressure by continuous evacuation through pumping. The introduction o~ the plasma torch and th~ substrate 14 in ~n underpres~ur2 chamber is not a requirement, sinae t~
oaating acc~rdin~ ~o the ~nvention can be produce~ al~o a~
atmospheric pr~ssur~ or even at a hi~her pre~sure.

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187~1 2~2~
The ~uel ya~ ~equir~d ~or th~ op~r~t:Lon o~ the pla~ma torch i~ argon or any othRr noble gas wi~h a certain proportion o~
hydrogen. ~he hydrogen has the propexty of eroding the gr~phit~
already formed during deposition, so that the presence o~
hydrogen also contributes ~o graphit~ reductio~. These phenomena howe~er are ~ow~ e.

The coating according to the inve~tion succeeds of course even then when carbon carrior i6 ~ad to the plasma flame 12 in the form o~ ~as or in ~he ~orm of a li~uid su~h a~ alcoho~, for instance in or opposite the powder inlet 8. Then it is lnsured $n any case that in the ~aval nozz~e inside the anode 2 no depo~its ~an ~orm.

The special element of the invention consists in the large va~iation possibilitie~ of the coating due to the chan~ o~
paran~eters. On the one hand, the substra.te is brou~ht more or le6~ alo5e to the zone o~ h~h radical dqlnsity, on the othe~
hand, ~n th~ area ~ low radical ~ensitie~s a car~ide producer i~
introduo~d in the matrix material, which in addition to the hydrogen, takes aar~ of the separation of ca~bon ~hi~h does n~
o~ndense into the diamond modt~ication. When the substrate i~
plaoed in an area wi~h high density of radic~ls, as a rule the su~strate ha~ t~ be cooled, whic~ howe~er i~ not a serious ob~tacle. ~he ~imples~ possibili~y of ~u~strate coolln~ is plasma spraying under water.

1~7~1 2 ~ ~
0~ cour~e, wlth the process o~ th~ l:nvenkion it is po3~bl~
~o aohiQv~ a ~radua~ion, ~.e. a ohange in the ra~io ~e~ween matrix and hard material embsdm~nt~, measuxed ov~r ~he lay~r thickn~s, In addition o~ a gxaduation between ~atrix ~n~
em~dment, it is o~ course al~o po6sible ~o achleve a multiple graduatio~, 50 ~or instance a tun~sten, tunysten-molybdenum or v~nadium layer ~an be spra~ed, which clowly change~ ovex lnto titanium o~ tantalum, which a~ain form th~ matri~ for the diamond parti~les. In a variant thareo~, in addition to the titanium or tantalum, ~t i5 po~si~le to ~orm a tran~i~ion to ~nother ~atrix ma~rial, e.g. a highl~ active caxbi~e producer, wha~eby then the aforemention~d layer s~rves as a barrier layer. Gen~rally, the invent~ on can be u~ed ev~ry~here a matrix has to be suacess~ully applied to a subs~at~, so that adhesion, porosity, tear re~istance and th~ like axe satisfa~tory.

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Claims (16)

PATENT CLAIMS

1. Process for applying a coating onto a substrate with the aid of a plasma torch as a thermal spraying technique, wherein the coating consists of a matrix as effective layer with embedments for improving the characteristics of the matrix or of a matrix as binder material with particles embedded therein constituting the actual effective layer, comprising the steps:
-operating a plasma torch with powder supply for matrix formation, -supplying a carbon-containing gas or liquid to the plasma torch as a reactive component for the formation of diamond-like, embedded, respectively bonded diamond particles, -adjusting the distance of the substrate to the nozzle of the plasma torch in order to determine the density of radicals in the immediate vicinity of the substrate, whereby a shorter distance results in a higher concentration and a distance approximately the length of the flame results in a lower density, -addition of carbide producers to the powder depending on the adjustment of the substrate distance with respect to the nozzle of the plasma torch, whereby a shorter distance requires a small addition and a distance approximately of the length of the plasma flame requires a larger addition, -optional cooling of the substrate when the distances to the nozzle of the plasma torch are short.

2. Process according to claim 1, wherein the carbon-containing gas or liquid is centrally supplied through a channel in the center of the plasma torch or is fed radially.

3. Process according to claim 1 or 2, characterized in that a carbon-dissolving element such as cobalt is added to the powder.

4. Process according to one of claims 1 to 3, wherein the powder for the matrix is metallic, ceramic or a mixture thereof, i.e. a cermet.

5. Process according to claim 1, wherein the supplied carbon-containing gas is methane (CH4).

6. Process according to claim 1, wherein hydrogen is fed in addition to the fuel gas of the plasma torch, in order to avoid the formation of graphite.

7. Process according to claim 1, wherein the plasma torch reactive gases containing silicon, nitrogen and/or boron are supplied to the plasma torch for the formation of further corresponding embedments.

8. A coating of composite material sprayed onto a substrate by means of plasma torch, consisting of a matrix as effective layer and embedments for improving the characteristics of the matrix or of a matrix as binder material and therein bonded particles forming the actual effective layer, whereby at least the matrix is formed of powder which is supplied to the plasma torch during the application of the coating, characterized in that in the matrix diamond-like particles are embedded, whose starting material consists of carbon-containing gas or carbon-containing liquid fed to the plasma torch.

9. Coating according to claim 8, characterized in that the matrix contains carbide producers such as titanium, chrome, hafnium or zirconium.

10. Coating according to claim 8 or 9, characterized in that the matrix is metallic, ceramic or a mixture thereof, i.e.
cermet.

11. Coating according to one claims 8 to 10, characterized in that that methane (CH4) can be supplied in a manner know per se as carbon-containing gas.

12. Coating according to one of claims 8 to 11, characterized in that hydrogen can be supplied in addition to the fuel gas, in order to avoid graphite formation.

13. Coating according to one of the claims 8 to 12, characterized in that in the matrix further inserts are embedded, namely silicon, nitrogen or boron compounds.

14. Plasma torch for spraying a coating according to one of claims 8 to 12, consisting of an annular anode, a central cathode, a powder inlet and at least one gas connection for the fuel gas, characterized in that an additional gas connection for the carbon-containing gas or the carbon-containing liquid is provided, traversing the cathode (3) as axial channel (10).

15. Plasma torch according to claim 14, characterized in that it can be operated at a pressure ranging between 50 mbar to 5 bar, which means also at atmospheric pressure.

16. Plasma torch according to claim 7 or 8, characterized in that the electric energy can be supplied as a direct current or as a high-frequency alternating field.