Peculiarities of surface adhesion based on nickel, produced by high-velocity spraying on steel base with different surface morphology have been analysed. It is shown that ultrasound final polishing builds up wavy submicrorelief providing the reliable adhesive connection between covering and base. Ultrasound finite polishing is suggested as a method of preparing surface for high-speed flame

Klimenov, V. А.

Kovalevskaya, Zh. G.

Tolmachev, А. I.

Zaytsev, К. V.

Electronic archive of Tomsk Polytechnic University

IntroductionIn the last 10–15 years the highvelocity oxygen fuelmethod of gasthermal coating has been effciently developed and improved in the world [1–3]. In comparisonwith gasflame and plasma methods the process of highvelocity oxygen fuel spraying possesses a number of advantages. Coatings produced by this technique are ofhigh density, adhesive and cohesive strength, fine andhomogeneous microstructure, low residual voltages [1].Oxidation of highvelocity oxygen fuel coating at hightemperature is rather less than it is of subsonic one [3].The values of density and adhesive strength of such coating are comparable with those of explosion and exceedsufficiently those parameters of plasma coating [1, 3].The modern equipment available at Yurga MachineBuilding plant has permitted for developing technologyof hydrocyllinder support shaft with reinforcing coating.However, quality control of the produced coating did notgive the complete account on interaction of the processparameters, produced structure and coating characteristics. Therefore, the purpose of the given paper is to investigate the interaction of coating with the base at different techniques of surface preparation before spraying.1. Materials and methods of investigationCoating was applied by means of highvelocity oxygen fuel device for antiwear, hightemperature, heatreflecting sealing coating [3], Fig. 1.Fig. 1. Scheme of installation: 1) gas bottle (propane); 2) vaporiser; 3) condenser; 4) receiver; 5) gas bottle (nitrogen);6) powder feeder; 7) burner; 8) pipes and cablesThe installation includes: burner, powder feeder, vaporiser, control board and a number of accessories.Structurally the burner consists of four main parts: readyfitted combustion chamber, gas dispenser, «secondary» propane dispenser, readyfitted nozzle frame.Powder feeder provides exact dosing and continuous feeding of powder into the burner. Powder is fed under thepressure of carrier gas, for which nitrogen or argon mayserve. Vaporiser serves as a phase transforming means ofpropane from liquid into gas. Inside the vaporizer propane is prepared for necessary parameters of pressureand temperature. Spraying is performed under the automatic mode. The control board with touch screen provides distance adjustment, regulation and stability of theprocess parameters.Specifications of the installation: velocity of gas outflow at the burner nozzle section is 800 m/sec; the flowof fuel gas (propane) is 250 l/min; the flow of carrier gasis (nitrogen) 40 l/min; oxidizer flow (compressed air) is7...9 m3/min; the capacity in spraying metals and alloysis up to 18 kg/h; the thickness of evaporated layer is0,03...10 mm; the coating porosity is less than 1,0 %;the total power input is not more than 5 kW.As an evaporated material the powder on the basis ofnickel ПРН65Х25С3Р3 (Fe – 5 wt. %; C – 1,5 wt. %;Cr – 26 wt. %; Si – 2,3 wt. %; В – wt. 3 %; Ni – therest) with the particle size 30...50 mkm was used [4].The sample spraying was performed at distance –200 mm; with the spraying angle 90°; linear velocity ofthe burner motion 21 mm/sec. Coating was formed inlayers of 500...800 mkm thick on the cylindrical samplesof the steel 20.The surface pretreatment was performed in severalways. Turning was carried out at TUM35 machine toolat the number of spindle revolutions – 900 rev/min andfeed – 0,07 mm/rev. The subsequent polishing was made at the same machinetool using the polishing sheetMirka ecowet of Р1000 grit. Ultrasonic treatment wasperformed by the device of final polishing UZGK02 of200 W capacity; of the indenter holddown pressure70...75 Н; the indenter vibration frequency 24 kHz. Thenumber of the shaft revolutions of lathe was100 rev/min; the feed was 0,2 mm/rev [5]. The sprayabrasive treatment was carried out in a special chamberby shotblaster that direct the electrocorundum particles of 1,5...2 mm porosity in the compressed puff withthe pressure 0,5...0,6 MPa and the velocity15...30 m/sec onto the work surface.Bulletin of the Томsк Pоlytеchnic University. 2007. V. 310. № 352UDC 621.793.71INVESTIGATION OF SURFACE ADHESION PRODUCED BY HIGHSPEED FLAME SPRAYINGV.А. Klimenov, Zh.G. Kovalevskaya*,**, К.V. Zaytsev, А.I. Tolmachev*Yurga Technological Institute of TPU*RAS Institute of Strength Physics and Material Science, Tomsk**Tomsk Polytechnic UniversityEmail: klimenov@tpu.ruPeculiarities of surface adhesion based on nickel, produced by highvelocity spraying on steel base with different surface morphologyhave been analysed. It is shown that ultrasound final polishing builds up wavy submicrorelief providing the reliable adhesive connectionbetween covering and base. Ultrasound finite polishing is suggested as a method of preparing surface for highspeed flame.The presented study is based on the optical analysisof the surface morphology with high accuracy of measurements performed at the profilometric complexMICRO MEASURE 3D station. The state of the basesurface before spraying and after coating detachmenthas been investigated. With the help of graphic programthe square of grip points of the base with coating [6].2. Results and discussionAt gasthermal spraying in air the pretreatment ofthe part surface before spraying is of great significance,since the state of surface is responsible for the quality ofadhesive bond at the «coatingbase» boundary [7–10].Highvelocity spraying specifies the specific conditionsfor particle precipitation of the material on the basewith superhigh velocity that provides high forwardpressure in flowing particles over the base, and hence,does not require complex morphology of the base surface. From the above mentioned facts, in the paper somemethods of the surface preparation before spraying aresuggested. After turning, along with the traditionalmethod of sprayabrasive surface treatment the technique of polishing surface preparation and ultrasonic final treatment has been suggested. The ultrasonic finaltreatment consists in plastic deformation of the basesurface layers by the instrument vibrating with ultrasound frequency [5]. The formed in this treatment cellular microrelief, finegrain, with high defect density ofcrystal composition structure, and internal compressions may provide the reliable adhesive bond [11].The surface relief after turning has a definite periodicity set by the turning modes, Fig. 2, а. The results ofprofilometric analysis has shown that the roughnesswidth on the tops amounts 0,13 mm with Rмах~9 mkmheight, the roughness Rа=1,15 mkm, Fig. 2, b. The surface morphology is defined by the quality of turning.аbFig. 2. State of sample surface of steel 20 after turning:а) morphology; b) profilogramAs the results of profilometric analysis showed, thesample surface after sprayabrasive treatment is presented by morphology consisting of a group of craters formed by the corundum particles after the strike on thesurface, Fig. 3, а.аbFig. 3. State of sample surface of steel 20 after sprayabrasivetreatment: а) morphology; b) profilogramIn the course of repeated influence of abrasive particles on the sample surface the equalization of itsroughness occurs (Rа=4,38 mkm) owing to chippingoffthe original micro asperities and overlaying the craters,Fig. 3, b. The formed relief has a sawtooth structurewith the asperity height up to 34 mkm.After turning and polishing the asperities of microroughness are smoothed to Rмах~6 mkm, due to whichthe support surface increases. The roughness decreasesto Rа=0,85 mkm, Fig. 4.аbFig. 4. State of sample surface of steel 20 after polishing:а) morphology; б) profilogramUltrasonic final polishing results in formation ofmicrorelief on the base surface conditioned by the relative motion of the smoothing tool and the sampleMathematics and mechanics. Physics53(Rа=0,7 mkm), Fig. 5. The formed microroughnessprofile in the direction of tool feed has the wavy structure with the roughness width 0,2 mm and the heightRz~4 mkm. Along the tool motion the submicrorelief setby repeated discrete pulse action of the tool is formed.The periodicity of the formed submicrorelief amountsapproximately 5 mkm, Fig. 5, b.аbFig. 5. State of sample surface of steel 20 after ultrasonic finaltreatment: а) morphology; b) profilogramOn the basis of the profilometric analysis it was stated that the maximum effective contact area is formed atsprayabrasive treatment of the base. In this case thesurface relief is shown by a group of sawtooth asperities,not oriented in the space. After polishing and ultrasonicfinal treatment the maximum effective area is less andnearly the same. However, geometry of polished profilesdiffers significantly. After polishing the directed tracesof cutting instrument remain on the sample surface.They are not removed in the process of polishing andform sharp marks. After ultrasonic final treatment therelief of the turning surface is smoothed and the submicrorelief consisting of the traces of ultrasonic devicemultiple strikes is formed.After mechanical detachment of the sprayed surfacefrom the involved surfaces the iterated profilometricanalysis with estimation of grip point area of the coatingwith the base.In all cases, when detaching the coating from thebase the surface has the following view: the grip pointsof the sprayed particles with the base alternate with theareas of the secondary oxidation. In profilograms theincrease in total value of roughness due to asperities formed by the sprayed particles remained after coating detachment, Fig. 6.The value of the total roughness includes the roughness of the areas having original relief and coated withnondetached particles. Thus, on the basis of surfaceroughness values after detachment one can estimatequalitatively the adhesion between the coating and thebase, prepared by different techniques.In Fig. 6, а, the profilogram of the base surface afterdetachment with preparatory sprayabrasive treatmentis presented. When comparing with Fig. 3, b, it is seenthat a part of the profile is formed by the base relief, theother one – by the sprayed particles. The roughnes ofthe formed surface Rа amounts 6,99 mkm.Fig. 6. Profilograms of the base surface after coating detachment: а) sprayabrasive treatment; b) polishing;c) ultrasonic final treatmentThe profiles of the base surface formed after coatingdetachment applied on the polished and ultrasonicallytreated surface have a complex view, Fig. 6, b, c. In thepicture of the formed profiles it is difficult to distinguishthe areas formed by the base relief and that of sprayedparticles. Nevertheless, the total roughness in both cases increases. Moreover, on the surface of ultrasonicallytreated surface it is twice as much.The quantitative estimation of sprayed surfaceadhesion was performed by estimation of the total areaof grip points of the sprayed particles and the base. It isknown that the more is the grip point area of the sprayed particles and the base, the higher is the adhesivestrength of coating [10].Тable. Results of estimation of adhesion between the coating and the baseWith the help of graphic program it was determinedthat when detaching the coating sprayed on the base afTechnique of the preparatory surface treatment Originalroughnessof the baseRа, mkmRoughnessafter coatingdetachmentRа, mkmTotal area ofparticle andbase grippoints, %Sprayabrasive 4,38 6,99 53Polishing 0,85 1,05 24Ultrasonic final treatment 0,7 1,97 38аbc   Bulletin of the Томsк Pоlytеchnic University. 2007. V. 310. № 354ter sprayabrasive treatment the grip point area is approximately 53 %, that corresponds to high indexes ofadhesive strength between the coating and the base[9, 10]. On the surface of the polished base the grip point area is approximately 24 %, but on that with the ultrasonic treatment it is approximately 38 %. The resultsof analysis in sample surface morphology after coatingdetachment and the values of the total grip point area ofthe coating and the base are listed.Thus, the estimation of the base surface state aftercoating detachment has shown that preparatory sprayabrasive treatment results in formation of strong bond atthe «coatingbase» composition boundary due to realisation of some activation channels and increase in contact area. Minimum roughness of the base surface treated by ultrasound as well as formation of wavy submicrorelief and modified structure of the surface layer provides the uniform influence of pulse and forward pressure of liquid drops of evaporated material on the base andpromote the mechanical activation channel over thewhole surface of the base [8–10]. The formed at theboundary adhesive bond between coating and the polished by ultrasound base meets the engineering requirements.ConclusionOn the basis of the conducted investigation of thebase surface morphology before and after coating and itsdetachment it has been determined:1. All investigated techniques of base surface preparation before spraying: sprayabrasive treatment, polishing and ultrasonic final treatment form at theboundary between coating and base effective adhesive bond. In this case the maximum square of grippoints between coating and base is formed on thesurface after sprayabrasive treatment, but minimum one is after polishing the base surface.2. Ultrasonic final polishing forms the wavy submicrorelief and modified structure on the base surface,providing the formation of reliable adhesive bondbetween coating and base. Ultrasonic final polishingis suggested as a method of surface preparation before highvelocity oxygen fuel coating.The authors are grateful for the assistance of the research workers of the Centre of Measurement of Physical and Operational Properties of New Materials and Coatings of the Scientific Research Institute of Nuclear Physics at Tomsk Polytechnic University and theworkers of Yurga Machinebuilding Plant.The work has been supported by RFBR, grants 060801220а. Mathematics and mechanics. Physics55REFERENCES1. Arvidsson P.E. Comparison of Superalloy Coatings Sprayed withPlasma and HVOF // Powder Metallurgy International. – 1991. –№ 3. – P. 176–179.2. Baldayev L.H., Shesterkin N.G., Lapanov V.А., Shatov А.P. Percularities of highvelocity oxygen fuel processes // Svarochnoye Proizvodstvo. – 2003. – № 5. – P. 43–46.3. Frolov V.А., Poklad V.А., Ryabenko B.V. Viktorenkov D.V. Technological features of super sound methods of gasthermal spraying //Svarochnoye Proizvodstvo. – 2006. – № 2. – P. 45–53.4. Borisov Yu.S., Kharlamov Yu.А., Sidorenko S.L., Ardatovskaya Е.N. Gasthermal coating of powder materials. Manual. –Kiev: Naukova dumka, 1987. – 544 p.5. Klimenov V.А., Kaminskiy P.P., Tolstov V.P., Kovalevskaya Zh.G.,Uvarkin P.V. Development of technology and equipment for ultrasonic treatment of locomotive wheel tread // Technologies of Repair,Reconstruction, Reinforcement, and Renovation of Machines,Mechanisms, Equipment and Metal Constructions: Mat. of the 5thIntern. Pract. Conf.Exibition. – SPb.: SPbSPU Edition, 2003. –P. 199–203.6. Klimenov V.А., Kovalevskaya Zh.G., Agafonova N.S., Tolmachev А.I, Zaytsev К.V., Ivanov Yu.F. Ultrasonic modification –the method of surface preparation before gasthermal spraying //Technologies of Repair, Reconstruction, and Reinforcement ofMachine Elements, Mechanisms, Equipment, Devices, and Tools:Mat. of the 8th Intern. Pract. Conf. – SPb., 2006. – Part 1. –P. 150–158.7. Solonenko О.P., Smirnov А.V., Klimenov V.А. et al. The role ofboundaries in formation of splats and coating structure // Phyzicheskaya Mezomechanica. – 1999. – V. 2. – № 1–2. – P. 123–140.8. Revun S.А., Balakirev V.F. Features of forming adhesive bond at gasthermal coating spraying // Phyzica i Chimiya Obrabotki Materialov.– 2002. – № 2. – P. 55–62.9. Sinolitsin E.К. Production of fast adhesion with base at lowvelocity gasflame spraying of liquid metal particles // Phyzica i ChimiyaObrabotki Materialov. – 2002. – № 2. – P. 49–54.10. Shmakov А.М., Yermakov S.S. Shock interaction of particle with thebase at gasthermal spraying // Phyzica i Chimiya Obrabotki Materialov. – 1986. – № 3. – P. 66–71.11. Klimenov V.А., Nekhoroshkov О.N., Uvarkin P.V., Kovalevskaya Zh.G., Ivanov Yu.F. Structure, phase composition and properties of steel 60, subjected to ultrasonic final polishing // Phyzicheskaya Mezomechanica. – 2006. – V. 9. – P. 173–176.Received on 11.12.2006

Investigation of surface adhesion produced by high-speed flame spraying

Abstract

Similar works

Full text

Available Versions

Electronic archive of Tomsk Polytechnic University