The article presents the results of examining properties of arc sprayed coating obtained with nano-alloy on the iron matrix with a high amount of fine carbide precipitates sprayed on non-alloyed steel plates intended for high temperature operation. Powder metal cored wire EnDOtec DO*390N 1,6 mm diameter, was used to produce, dense, very high abrasion and erosion resistant coatings approx. 1,0 mm thick. Nano-material coatings characterization was done to determine abrasion resistance, erosion resistance, adhesion strength, hardness as well as metallographic examinations. Results have proved high properties of arc sprayed nano-material coatings and have shown promising industrial applications

A. Czupryński

J. Gorka

M. Adamiak

English

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173METALURGIJA 55 (2016) 2, 173-176A. CZUPRYŃSKI, J. GORKA, M. ADAMIAKEXAMINING PROPERTIES OF ARC SPRAYED NANOSTRUCTURED COATINGSReceived – Primljeno: 2015-04-08Accepted – Prihvaćeno: 2015-10-20Original Scientific Paper – Izvorni znanstveni radA. Czrupynski,  J. Gorka, M. Adamiak, Silesian University of Technol-ogy, Gliwice, PolandThe article presents the results of examining properties of arc sprayed coating obtained with nano-alloy on the iron matrix with a high amount of fine carbide precipitates sprayed on non-alloyed steel plates intended for high tem-perature operation. Powder metal cored wire EnDOtec DO*390N 1,6 mm diameter, was used to produce, dense, very high abrasion and erosion resistant coatings approx. 1,0 mm thick. Nano-material coatings characterization was done to determine abrasion resistance, erosion resistance, adhesion strength, hardness as well as metallo-graphic examinations. Results have proved high properties of arc sprayed nano-material coatings and have shown promising industrial applications.Key words: coating, wire arc spraying, nano-alloys, abrasive and erosion wear, adhesion strengthINTRODUCTIONDynamic expansion of nanotechnologies, which are one of the most intensely growing technologies, has been observed for the last few year’s [1, 2]. Nanotech-nology also has an impact on the significant develop-ment of surface engineering and welding technologies. For the present, it is possible to obtain high quality na-nostructure layers e.g. aluminium alloys for car engine parts, or copper alloys for ships screw propellers.Continuous development of welding engineering in scope of equipment construction and filler materials met-allurgy gives possibilities to obtaining surface layers pro-viding special extreme properties, e.g.: thermal barrier coatings, gradient layers, high-hardness layers, wear-, erosion- and corrosion-resistant layers or biocompatible coatings [1, 3-8]. One of the modern surface engineering technologies assuring high quality surface layers is wire arc spraying process, where spraying of metallic layer is made without melting the base material, layer is mechan-ically or adhesively bonded with the base material, a pair of solid or cored metal wires is feed with constant speed and is melted by electric arc heat with precisely con-trolled current and voltage, Figure 1 [9].Melted filler material is atomized by compressed air and then thrown onto the surface of base metal. Melted particles of wires hit the base metal, and solidify after quick cooling. Wire arc spraying process ensures high quality coatings characterized by low porosity and very strong adhesion or mechanical bond to the base metal and is successfully applied in modern industry in the production of new parts or as the repair process of worn parts [1, 9].ISSN 0543-5846METABK 55(2) 173-176 (2016)UDC – UDK 621.793:72:621.778:621:365.2:620.178.1=111The examination results of the welding procedure (Table 1) of nano-material EnDOtec DO*390N wire arc spraying on a base metal, Grade 55 steel sheet allowed to establish optimum welding conditions of spraying high quality surface layers 1,0 mm thick. Study of struc-ture, grain size, hardness, wear and erosion resistance and adhesion strength to base metal of DO*390N wire arc sprayed coatings proved their high quality.E XPERIMENTAL PROCEDURET est were conducted to determine the structure, size of grain, hardness, abrasion wear resistance and adhe-sion strength to the base of arc sprayed layer on non-alloyed ASTM A516, Grade 55 steel plates intended for high-temperature operation, obtained with EnDOtec DO*390N powder wire.Figure 1  A scheme of wire arc spraying apparatus: 1 – compressed air; 2 – wire electric contact; 3 – sprayed layer; 4 – base metal; 5 – electric arc; 6 – wire feeder; 7 – compressed air [9].174A. CZUPRYŃSKI et al.: EXAMINING PROPERTIES OF ARC SPRAYED NANOSTRUCTURED COATINGS METALURGIJA 55 (2016) 2, 173-176The influence of wire arc spraying parameters on the quality of sprayed coatings on the clean surface of Grade 55 steel sheets was tested at wide range of arc current, arc voltage, wire feed speed, atomizing air pressure and distance between torch and surface of the base metal. Arc spraying tests of 1,0 mm thick layers were conducted in vertical position on a manufacturing stand equipped in the EuTronic Arc Spray 4 arc wire spraying equipment and hand spraying gun, Gun 4.200 χ 200 χ 9 mm steel sheets were sand blasted and preheated with a gas burner to the temperature of about 40 oC just before wire arc spraying process. The range of optimum wire arc spraying parameters was defined on the basis of following quality criteria of sprayed coatings: uniform thickness of coating, low porosity and high adhesion strength of coating to the base metal, Table 1.RESULTS AND DISCUSSIONPorosity of DO*390N wire arc sprayed coatings was evaluated in accordance to ASTM B - 276 standard. Po-rosity was defined using Materials-Pro Analyser. The software used calculated the overall number of pixels on scanned surface of the sample and determined the per-centage amount of black pixels (empty spaces). Tests of grinded surface of external layer on 1,0 cm2 area in Ma-terials-Pro Analyser software have shown that porosity is at the range 5 - 10 %. Metallographic macro and micro structure examinations proved very high quality of DO*390N wire arc sprayed coatings, with uniform bond-ing with base metal and limited porosity, Figure 2a, b. Results of the X-ray phase analysis show peaks from Cr7C3 and Fe3C as well as from Fe α. Grain size measure-ments of DO*390N wire arc sprayed layer microstruc-ture were conducted on PANalytical Xpert PRO roentgen diffractometer. Based on crystallite size calculations us-ing Scherrer’s equation (1) it was found that the average grain size of arc sprayed coating, measured in perpen-dicular direction to the base, is around 28,6 nm.where:D – average crystallite size in perpendicular direction to the deflection plane, K – Scherrer’s factor (nearly 1) λ – wave length used, Bstruct. – the structural broadening which is the difference in integral profile width between a standard and the sample to be analysed, θ – describes the angle of incidence.HV 0,1 hardness tests were conducted on ground surface of arc sprayed coating in six measurement points, in accordance to ISO 6507-1:2007 standard. The average hardness of the coating was 873 HV0,1 (63 HRC). Abrasion wear resistance tests were conducted in accordance to ASTM G65-00 standard, Procedure A [10]. 75 χ 25χ 10 mm samples were cut out in the mid-dle of arc sprayed plate and HARDOX 400 steel and minimally grinded. All of samples, acc. to demands of standard, before and after the tests were weighed on lab scale with 0.0001 g accuracy. Weight loss of DO*390N wire arc sprayed coatings was compared directly to HARDOX 400 steel plate volume loss. Using measured density of sprayed layer and weight loss of the sample also volume weight loss was calculated, Table 2. Quan-titative assessment of erosion wear resistance of DO*390N wire arc sprayed coatings and HARDOX 400 steel plate was conducted in accordance to ASTM G76-95 [11]. Erosion resistance was tested on the same specimens used for abrasion wear resistance tests. Be-fore the tests, ASTM G76-95 apparatus was calibrated on AISI 1020 steel plate specimen to set the stable flow of erosion particles and define reference erosion value. Erosion resistance of DO*390N wire arc sprayed coat-ings and HARDOX 400 steel plate were tested at ero-sion particles impingement angle: 90o, 60o, 30o and 15o, Table 3.Adhesion strength tests of DO*390N wire arc sprayed coatings to the surface of ASTM A516, Grade 55 steel sheets were conducted in accordance to ASTM C 633-01 standard [12]. 25 mm diameter samples were cut from sprayed test plate and glued together using Henkel Loctite®Hysol® 348 A&B Superior Metal glue. Properly prepared samples were exposed to the static tensile test lasting till their damage. Failure of all tested specimens took place in the centre part of arc sprayed coatings, with adhesion strength above 10 N/mm2, Table 4. CONCLUSIONSBased on the results of arc spraying using 1,6 mm diameter, DO*390N grade powder wire of non-alloyed ASTM A516, Grade 55 steel, one can conclude that it is a)b)Figure 2  Macro (a) and microstructure (b) of DO*390N wire arc sprayed coating, etching: HCl+ HNO3175A. CZUPRYŃSKI et al.: EXAMINING PROPERTIES OF ARC SPRAYED NANOSTRUCTURED COATINGSMETALURGIJA 55 (2016) 2, 173-176Table 1 Properties of EnDOtec DO*390N wire weld metal and optimum wire arc spraying parametersWire designationChemical composition / mas.% and typical hardness of deposit (by CASTOLIN)Arc spraying parametersCurrent /A Voltage /V Gun distance from base metal sheet /mmEnDOTecDO*390NFe + < 5,0 C,< 2,0 Si, < 5,0 Mn, < 20,0 Cr, < 10,0 Mo,< 10,0 Nb, < 10,0 W, < 5,0 B 71 HRC 160 - 170 30,0 - 31,0 180 - 190Remarks: EnDOtec DO*390N wire dia. 1,6 mm. Preheating temperature of base metal sheet 40 oC. Air pressure 5,5 - 5,8 barTable 2 Results of low-stress abrasion wear resistance to metal-ceramic scratchingSpecimen designationNumber of specimenWeight before test/ gWeight after test/ gMass loss/ gAverage mass loss/ gAverage volume loss/ mm3Relative* abrasion resistanceDO390NN1 127,3654 126,1191 1,24631,2335 191,5373 0,99N2 128,3998 127,1791 1,2207HARDOX 400H1 62,2260 60,7526 1,47341,4617 185,7306 1,00H2 63,1222 61,6721 1,4501Remarks: density of DO*390N wire arc sprayed coating: – 6,44 g/cm3, the force applied against the test specimen TL = 130 N. Volume loss, mm3 = (mass loss g : density g/cm3) x 1000. * - relative to HARDOX 400 steel plate.Table 3 Results of erosion wear resistance testsSpecimen designationErodent impact angle/ oNo of speci-menErosion weight loss/ mgErosion rate/ mg/minErosion value/0,001mm3/gAverage erosion value/ 0,001 mm3/gRelative erosion resistance*DO390N90390N-90-1 14,8 1,48 113,4882113,1048 0,36390N-90-2 14,7 1,47 112,7214HARDOX 400400-90-1 6,5 0,65 40,786240,7862 1.,0400-90-2 6,5 0,65 40,7862DO390N60390N-60-1 22,9 2,29 175,6000176,3668 0,27390N-60-2 23,1 2,31 177,1337HARDOX 400400-60-1 7,4 0,74 46,433646,7473 1,0400-60-2 7,5 0,75 47,0610DO390N30390N-30-1 14,7 1,47 112,7214111,9546 0,42390N-30-2 14,5 1,45 111,1878HARDOX 400400-30-1 7,6 0,76 47,688547,3748 1,0400-30-2 7,5 0,75 47,0610DO390N15390N-15-1 14,8 1,48 113,4882113,1048 0,43390N-15-2 14,7 1,47 112,7214HARDOX 400400-15-1 7,6 0,76 47,688548,3160 1,0400-15-2 7,8 0,78 48,9435Remarks: Erosion rate, mg/min = (mass loss mg : time plot min), Erosion value, mm3/g = (volume loss of specimen mm3 : total mass of abrasive particles g). Erosion conditions: velocity – 70 ± 2 m/s, temperature 20 oC, erodent – Al2O3 of nominal dimension – 50 μm, feed rate – 2,0 ± 0,5 g/min., erosion time – 10 min, distance between nozzle and specimen – 10 mm, test temperature 20 oC, * – relative to HARDOX 400 steel plate.Table 4 Results of adhesion strength testsDesignation of test specimensNumber of test specimenMax. load at rapture/ kNSpecimencross-sectional area/ mm2Adhesion strength/ N/mm2Average adhesion strength/ N/mm2DO390N DO1 5,9 490,6 11,9 10,9DO2 5,2 10,5DO3 5,1 10,4possible to obtain high-quality, nano-structural layer with medium sized crystallites below 30 nm. Results of study of influence of basic parameters of EnDOtec DO*390N wire arc spraying process on the quality of nano-structural coatings proved that it is possible to produce high quality, approx. 1,0 mm thick coatings, characterized by low porosity in the range 5 – 10 %. Sprayed layer is characterized by high hardness over 63 HRC and abrasion wear resistance comparable to pa-rameters of HARDOX 400. Erosion resistance at parti-cle impingement angles from 15o to 30o is high however 40 % lower than HARDOX 400 steel plate. Adhesion strength tests of arc sprayed layer with EnDOtec DO*390N nanoalloy on ASTM A516, Grade 55 steel were conducted acc. to ASTM C 633 - 01 standard and have shown adhesive-mechanical character of layer/base material bonding above 10 MPa. Binder material EnDOtec DO*390N is a modern material for arc spray-ing of high hardness, abrasion and erosion wear resist-ant layer.176A. CZUPRYŃSKI et al.: EXAMINING PROPERTIES OF ARC SPRAYED NANOSTRUCTURED COATINGS METALURGIJA 55 (2016) 2, 173-176REFERENCES[1] Ch. P. Jr Poole, F. J. Ownes, Introduction to Nanotechnol-ogy, Wiley, New Jersey, 2003, 1-8.[2] S. Boncel, J. Gorka, M. Shaffer, K. 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Examining properties of arc sprayed nanostructured coatings

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