organic finishing · stru ctu red and amorphou s materi-als . in nano-s tru ctu red materials , g...

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www.organicfinishing.com J anu ary 2010 I metalfinishing I 37 Current and Future Applications of Cold Spray Technology C old spray is one of the many names for desc rib ing a solid- state c oating proc ess that u ses a hig h-speed g as jet to ac c elerate pow - der partic les tow ard a su b strate w hereb y metal partic les plastic ally deform and c onsolidate u pon impac t. T he term “ c old spray” refers to the relativ ely low proc ess temper- atu re inv olv ed in the proc ess, w hic h is typic ally mu c h low er than the melting point of the spray material. A lthou g h the c onc ept of c old spraying metallic materials onto su b- strates g oes b ac k to the early 19 0 0 s, it w as not u ntil the 19 8 0 s that the applic ab ility of this tec hnolog y w as demonstrated at the Institu te of T heoretic al and A pplied M ec hanic s of the R u ssian A c ademy of S c ienc es in N ov osib irisk . B ec au se adhesion of the metal pow der to the su b strate and deposited material is ac hiev ed in the solid state, the c harac teristic s of c old spray deposits are q u ite u niq u e, mak ing c old spray su itab le for depositing a w ide rang e of tradi- tional and adv anc ed materials on many types of su b strate materials, espec ial- ly in non-traditional applic ations that are sensitiv e to the temperatu re of the proc ess. S ome of the c harac teristic s of c old spray inc lu de the ab ility to form dense deposits w ith ex tremely low ox yg en c ontent, free of residu al ten- sile stresses, g rain g row th, rec rystal- liz ation z ones, and phase c hang es. C ertain materials may ev en ex peri- enc e g rain refinement at the nanometer sc ale. T hese attrib u tes mak e c old spray u niq u ely su itab le for depositing a rang e of adv anc ed and temperatu re-sensitiv e materials. T oday, c old spray is inc reasing ly b eing u sed in a nu mb er of indu stries, inc lu ding aerospac e, energ y, and mil- itary (F ig s. 1 and 2). HOW DOES COLDSPRAY WORK? B ac k in the 19 8 0 s, du ring the prac ti- c al dev elopment of c old spray tec h- nolog y, tw o methods of injec ting the spray materials into the noz z le w ere patented, lead- ing to w hat is k now n today as hig h pressu re (injec ting the pow der prior to the spray noz z le throat from a hig h-pres- su re g as su pply) 1 and low pressu re (injec ting the pow der in the div erg - ing sec tion of the spray noz z le from a low -pressu re g as su pply). 2 I n hig h-pressu re c old spray ( F ig . 3 ), heliu m or nitrog en at hig h pressu re (u p to 1,0 0 0 psi) is preheated (u p to 1,0 0 0 ° C ) and then forc ed throu g h a c onv erg ing -div erg ing DeLaval noz z le. A t the noz z le, the ex pansion of the g as produ c es the c onv ersion of enthalpy into k inetic energ y, w hic h ac c elerates the g as flow to su person- ic reg ime (1,0 0 0 m/ s) w hile redu c ing its temperatu re. T he pow der feed- stoc k is introdu c ed ax ially into the g as stream, prior to the noz z le throat. T he ac c elerated solid parti- c les impac t the su b strate w ith enou g h k inetic energ y to indu c e mec hanic al and/ or metallu rg ic al b onding . In low -pressu re c old spray (F ig . 4 ), air or nitrog en at relativ ely low pres- su re (8 0 – 14 0 psi) is also preheated (u p to 5 5 0 ° C ) , then forc ed throu g h a DeLaval noz z le. A t the div erg ing side of the noz z le, the heated g as is ac c el- erated to ab ou t 6 0 0 m/ s. P ow der feedstoc k is introdu c ed dow nstream in the div erg ing sec tion and ac c eler- ated tow ard the su b strate. O RG AN IC finishing JULIO VILLAFUERTE, CENTERLINE WINDSOR, LTD., WINDSOR, ONTARIO, CANADA Figure 1: Field repair of corrosion surface damage by low- pressure cold spray. Figure 2: Cold spray fab rication of conductiv e busb ars ov er tin ox ide- coated glass for heated glass applications.

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Page 1: ORGANIC finishing · stru ctu red and amorphou s materi-als . In nano-s tru ctu red materials , g rain siz es are ex tremely small and prov ide mechanical adv antag es su ch

www.organicfinishing.com January 2010 I metalfinishingI 37

Current and Future Applications of Cold Spray Technology

Cold spray is one of the manynames for desc rib ing a solid-

state c oating proc ess that u ses ahig h-speed g as jet to ac c elerate pow -der partic les tow ard a su b stratew hereb y metal partic les plastic allydeform and c onsolidate u ponimpac t. T he term “ c old spray” refersto the relativ ely low proc ess temper-atu re inv olv ed in the proc ess, w hic his typic ally mu c h low er than themelting point of the spray material.

A lthou g h the c onc ept of c oldspraying metallic materials onto su b -strates g oes b ac k to the early 19 0 0 s,it w as not u ntil the 19 8 0 s that theapplic ab ility of this tec hnolog y w asdemonstrated at the I nstitu te ofT heoretic al and A pplied M ec hanic sof the R u ssian A c ademy of S c ienc esin N ov osib irisk . B ec au se adhesion ofthe metal pow der to the su b strateand deposited material is ac hiev ed inthe solid state, the c harac teristic s ofc old spray deposits are q u ite u niq u e,mak ing c old spray su itab le fordepositing a w ide rang e of tradi-tional and adv anc edmaterials onm a n y

types of su b strate materials, espec ial-ly in non-traditional applic ationsthat are sensitiv e to the temperatu reof the proc ess.

S ome of the c harac teristic s of c oldspray inc lu de the ab ility to formdense deposits w ith ex tremely lowox yg en c ontent, free of residu al ten-sile stresses, g rain g row th, rec rystal-liz ation z ones, and phase c hang es.C ertain materials may ev en ex peri-enc e g rain refinement at thenanometer sc ale. T hese attrib u tesmak e c old spray u niq u ely su itab lefor depositing a rang e of adv anc edand temperatu re-sensitiv e materials.T oday, c old spray is inc reasing lyb eing u sed in a nu mb er of indu stries,inc lu ding aerospac e, energ y, and mil-itary ( F ig s. 1 and 2) .

HOW DOES COLD SPRAY WORK?

B ac k in the 19 8 0 s, du ring the prac ti-c al dev elopment of c old spray tec h-nolog y, tw o methods of injec ting the

spray materials into thenoz z le w ere patented, lead-

ing to w hat is k now ntoday as hig h

p r e s s u r e

(injec ting the pow der prior to thespray noz z le throat from a hig h-pres-su re g as su pply) 1 and low pressu re(injec ting the pow der in the div erg -ing sec tion of the spray noz z le from alow -pressu re g as su pply) .2

In hig h-pressu re c old spray ( F ig . 3 ) ,heliu m or nitrog en at hig h pressu re( u p to 1,0 0 0 psi) is preheated ( u p to1,0 0 0 ° C ) and then forc ed throu g h ac onv erg ing -div erg ing DeLaval noz z le.A t the noz z le, the ex pansion of theg as produ c es the c onv ersion ofenthalpy into k inetic energ y, w hic hac c elerates the g as flow to su person-ic reg ime (1,0 0 0 m/ s) w hile redu c ingits temperatu re. T he pow der feed-stoc k is introdu c ed ax ially into theg as stream, prior to the noz z lethroat. T he ac c elerated solid parti-c les impac t the su b strate w ithenou g h k inetic energ y to indu c emec hanic al and/ or metallu rg ic alb onding .

In low -pressu re c old spray ( F ig . 4 ) ,air or nitrog en at relativ ely low pres-su re ( 8 0 – 14 0 psi) is also preheated(u p to 5 5 0 ° C ) , then forc ed throu g h aDeLaval noz z le. A t the div erg ing sideof the noz z le, the heated g as is ac c el-erated to ab ou t 6 0 0 m/ s. P ow derfeedstoc k is introdu c ed dow nstreamin the div erg ing sec tion and ac c eler-ated tow ard the su b strate.

O RG AN IC finishing

JULIO VILLAFUERTE, CENTERLINE WINDSOR, LTD.,

WINDSOR, ONTARIO, CANADA

Figure 1: Field repair of corrosion surface damage by low-pressure cold spray.

Figure 2: Cold spray fabrication of conductive

busbars over tin oxide-coated glass for heated

glass applications.

Page 2: ORGANIC finishing · stru ctu red and amorphou s materi-als . In nano-s tru ctu red materials , g rain siz es are ex tremely small and prov ide mechanical adv antag es su ch

FUTURE TRENDS

There are new developments in coldspray technolog y , inclu ding shock -wave-indu ced spray ing ,3 – 6 whereb ythe fast opening / closing of a controlvalve downstream of a hig h-pressu reg as sou rce g enerates a pu lsed ( 1 0 – 3 0H z ) heated su personic f low ( F ig . 6 ) .The pu lsed f low is u sed to simu lta-

A s the applicab ility of cold spraytechnolog y ex pands to new andu niq u e areas of application, therehas b een an increasing nu mb er ofcommercially availab le, ready -to-u secold spray sy stems introdu ced intothe mark etplace ( F ig . 5 ) .

neou sly accelerate and heat the pow-der, which is introdu ced in a cy lin-drical noz z le. In contrast with coldspray , a DeLaval noz z le is notreq u ired, and powders can g ain addi-tional energ y du ring acceleration.This ef fectively facilitates b ondingfor a wide rang e of eng ineering mate-rials, inclu ding steels, titaniu m, andcermets. A lso, the intermittent g asf low lowers g as consu mption andincreases energ y ef f iciency .

ADVANCED APPLICATIONS

C old spray technolog y falls u nderthe larg er family of thermal sprayprocesses, and it is not here toreplace any of the well-estab lishedthermal spray methods. Instead, coldspray technolog y is ex pected to su p-plement and ex pand the rang e ofapplications for thermal spray .

In its cu rrent state, cold spray isincreasing ly u sed in a variety ofindu stries for corrosion mitig ationof sensitive materials, su ch as: mag -nesiu m and alu minu m alloy s; su r-face restoration; manu factu ring ofspu ttering targ ets; f ab rication ofb u sb ars on heated g lass; depositionof W C -C o for hard-chrome replace-ment coating s; electrical and thermalcondu ctive coating s for transitionsu rfaces; b raz e joint preparation; anddeposition of N iC rA lY b ond coatsfor thermal b arriers. F or many ofthese applications, cold spray pres-ents itself as a more economicalmethod b ecau se it can actu ally elim-inate or redu ce fab rication steps.

F or other applications, cold spray issimply the only viab le solu tion, espe-cially for an increasing nu mb er of

ORGANICfinishing

Figure 3: Operating principle of high-pressure cold spray.

Figure 4: Operating principle of low-pressure cold spray.

Figure 5: Commercially available low-pressurecold spray systems, including portable systemsintended for field operation.

(Image courtesy of CenterLine Windsor, Ltd.)

Figure 6: Shockwave-induced spraying (SISP).

38 I m etalfinishingI January 2010 www.metalfinishing.com

Page 3: ORGANIC finishing · stru ctu red and amorphou s materi-als . In nano-s tru ctu red materials , g rain siz es are ex tremely small and prov ide mechanical adv antag es su ch

www.organicfinishing.com January 2010 I metalfinishingI 39

NANOTECHNOLOGY AND

SMART STRUCTURES

Some other non-traditional applica-tions inv olv e the u tiliz ation ofadv anced materials , s u ch as nano-s tru ctu red and amorphou s materi-als . I n nano-s tru ctu red materials ,g rain s iz es are ex tremely s mall andprov ide mechanical adv antag es s u chas ex treme f ractu re tou g hnes s w hilemaintaining a hig h lev el of materials treng th. N ano-cry s tallinity is q u ites ens itiv e to proces s temperatu re, andcold s pray can ef fectiv ely b e u s edw ithou t compromis ing their b enef i-cial micros tru ctu re ( F ig . 8 ) .

B ecau s e of its low -temperatu redepos ition, cold s pray can b e u s ed toemb ed micro-s ens ors , along w ithf u nctional coating s , on s u rfaces fors mart s tru ctu res . T hes e s tru ctu resw ou ld hav e the ab ility to prov idereal-time inf ormation related tomaterials performance or env iron-mental conditions . T here are a nu m-b er of emerg ing enterpris es that arefocu s ing on prov iding s olu tions fors ens ing , datab as e manag ement, andprog nos tics analy s is in b ridg es ,pow er g rids , w ind tu rb ines , aircraf ts ,au tomob iles , s hips , pipelines , andcons tru ction eq u ipment. T he f u tu reof cold s pray relies on its ab ility todepos it adv anced materials onto adiv ers ity of s u b s trates w ith mini-mu m thermal penalty and cos t.T hes e are the corners tones that w illdef ine the direction and opportu ni-ties ly ing ahead for this technolog y .

NOTES

1 . A lk himov , A .P ., P apy rin A .N .,K os arev , V .F ., N es terov ich, N .I .,Shu s hpanov , M .M . G as -dy namics pray ing method for apply ing acoating . U S P atent 5 ,3 0 2 ,4 1 4 ,A pr. 1 2 , 1 9 9 4 .

2 . K as hirin, A .I ., K ly u ev , O .F .,B u z dy g ar, T . V . A pparatu s forg as -dy namic coating . U S P atent6 ,4 0 2 ,0 5 0 , J u ne 1 1 , 2 0 0 2 .

3 . Jodoin, B ., R icher, P ., B é ru b é , G .,A jdels z tajn, L ., Y andou z i, M .P u ls ed-g as dy namic s pray ing :proces s analy s is , dev elopmentand s elected coating ex amples .Surface and Coatings Technology2 0 0 7 ;2 0 1 ( 1 6 – 1 7 ) : 7 5 4 4 – 5 1 .

non-traditional applications . W hileenv ironmental and health & s afetyreg u lations hav e b ecome more s trin-g ent, interes t in cold s pray has g row nas a potentially g reener alternativ e.

A s the technolog y ev olv es it isanticipated that cold s pray applica-b ility w ill continu e to ex pand tomore non-traditional applications ,s u ch as photov oltaic, w ind, medical,and architectu ral. I n photov oltaicapplications , cold s pray cou ld b eu s ed for the fab rication of complexcondu ctiv e patterns in s olar cells( F ig . 7 ) . W ind pow er g eneration mayb e ab le to mak e u s e of cold s pray toenhance s u rf ace perf ormance incomponents made of adv anced poly -mer-matrix compos ites .

In the medical f ield, cold s pray hasalready b een demons trated to ef fec-tiv ely apply hy drox y apatite ( H A P ) , aw ell-k now n b io-compatib le material,to a nu mb er of s u b s trates w ithou tcompromis ing the integ rity of H A P .A rchitects can tak e adv antag e of colds pray to create u nlimited aes theticmetallic patterns on any metal orceramic s u b s trate.

4 . Y andou z i, M ., Jodoin, B .M icros tru ctu re and properties ofW C -b as ed coating s prepared b ypu ls ed g as dy namic s pray ingproces s : inf lu ence of proces s v ari-ab les . Surface and CoatingsTechnology 2 0 0 8 ;2 0 3 ( 1 – 2 ) : 1 0 4 – 1 4 .

5 . Y andou z i, M ., Jodoin, B . W C -b as ed compos ite coating s pre-pared b y the pu ls ed g as dy namics pray proces s : ef f ect of the feed-s tock pow ders . Surface andCoatings Technology 2 0 0 8 ;2 0 2 ( 1 6 ) :3 8 6 6 – 7 7 .

6 . Y andou z i, M ., Sans ou cy , E .,A jdels z tajn, L ., Jodoin, B . W C -b as ed cermet coating s produ cedb y cold g as dy namic and pu ls ed-g as dy namic s pray ing proces s es .Surface and Coatings Technology2 0 0 7 ;2 0 2 ( 2 ) : 3 8 2 – 9 0 .

BIO

D r. J ulio V illafuerte is the director ofresearch & dev elop m ent at CenterL ineW indsor L td., one of N orth A m erica’s p re-m ier designers and m anufacturers ofm etal form ing and w elding eq uip m ent,sup p lying m any of the w orld’s leadingv ehicle m anufacturers. D r. V illafuerte,also currently an adjunct p rofessor for theU niv ersity of W aterloo, w ith activ einv olv em ent in lecturing and research,holds P h.D . and m aster’s degrees inm echanical & m aterials engineering fromthe U niv ersity of W aterloo. H e has m orethan 1 5 years of ex p erience in w elding andm aterials p rocessing technology and has,for the last few years, com m itted toresearch and dissem ination of the new coldgas dynam ic sp ray technology.

D r. V illafuerte is v ery activ e in theindustrial com m unity, including theI nternational Therm al Sp ray A ssociationand A SM ’s Therm al Sp ray Society. H e isthe author of num erous technical p ub lica-tions and regularly v olunteers as techni-cal/ strategic adv isor to a num b er of p ro-fessional and academ ic com m ittees. D r.V illafuerte serv es as a technical rev iew erfor the A SM Jou rnal of M aterialsE ng ineering and P erformance, theJou rnal of P hotochemis try andP hotob iolog y & C hemis try , andSu rface and C oating s T echnolog y .

O RG AN IC finishing

Figure 7: Array of thin-film photovoltaic panels

powering an entire building at the University of

Toledo campus, Toledo, Ohio, USA.

Figure 8: Nano-structured 2618 aluminum alloy

deposited by the cold spray process.