MD561Z - Process for anticorrosion machining of steel - Google Patents
Process for anticorrosion machining of steel Download PDFInfo
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- MD561Z MD561Z MDS20120031A MDS20120031A MD561Z MD 561 Z MD561 Z MD 561Z MD S20120031 A MDS20120031 A MD S20120031A MD S20120031 A MDS20120031 A MD S20120031A MD 561 Z MD561 Z MD 561Z
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- Moldova
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- steel
- coating
- machining
- electrolyte
- pores
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 37
- 239000010959 steel Substances 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 15
- 238000003754 machining Methods 0.000 title abstract 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 25
- 238000000576 coating method Methods 0.000 claims abstract description 21
- 238000005260 corrosion Methods 0.000 claims abstract description 21
- 238000005275 alloying Methods 0.000 claims abstract description 17
- 239000011248 coating agent Substances 0.000 claims abstract description 17
- 239000011148 porous material Substances 0.000 claims abstract description 15
- 238000010892 electric spark Methods 0.000 claims abstract description 9
- 239000003792 electrolyte Substances 0.000 claims abstract description 9
- 229910017464 nitrogen compound Inorganic materials 0.000 claims abstract description 4
- 150000002830 nitrogen compounds Chemical class 0.000 claims abstract description 4
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 4
- 229920001864 tannin Polymers 0.000 claims abstract description 4
- 235000018553 tannin Nutrition 0.000 claims abstract description 4
- 239000001648 tannin Substances 0.000 claims abstract description 4
- 239000011810 insulating material Substances 0.000 claims abstract description 3
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 claims description 22
- 235000011007 phosphoric acid Nutrition 0.000 claims description 14
- 235000010288 sodium nitrite Nutrition 0.000 claims description 11
- 239000010410 layer Substances 0.000 claims description 10
- 239000002344 surface layer Substances 0.000 claims description 4
- 230000007797 corrosion Effects 0.000 abstract description 19
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 abstract description 6
- 235000010344 sodium nitrate Nutrition 0.000 abstract description 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 abstract 1
- 238000004519 manufacturing process Methods 0.000 abstract 1
- 238000011089 mechanical engineering Methods 0.000 abstract 1
- 239000004317 sodium nitrate Substances 0.000 abstract 1
- 238000004090 dissolution Methods 0.000 description 10
- 238000002161 passivation Methods 0.000 description 10
- 239000000956 alloy Substances 0.000 description 6
- 229910045601 alloy Inorganic materials 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 150000004767 nitrides Chemical class 0.000 description 4
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 3
- 229920002253 Tannate Polymers 0.000 description 3
- 235000019270 ammonium chloride Nutrition 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 238000005137 deposition process Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 239000007832 Na2SO4 Substances 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 210000003298 dental enamel Anatomy 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004299 exfoliation Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 238000009828 non-uniform distribution Methods 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
Landscapes
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Abstract
Description
Invenţia se referă la procedeele electrice şi termochimice de prelucrare a pieselor din oţel şi poate fi folosită în industria construcţiilor de maşini şi în construcţia aparatelor pentru mărirea rezistenţei la coroziune a pieselor maşinilor, sculelor şi utilajului tehnologic. The invention relates to electrical and thermochemical processes for processing steel parts and can be used in the machine building industry and in the construction of devices to increase the corrosion resistance of machine parts, tools and technological equipment.
Se cunoaşte un procedeu de aliere cu scântei electrice a suprafeţelor metalelor, eficient la modificarea compoziţiei chimice şi a proprietăţii straturilor superficiale ale materialelor metalice, bazată pe utilizarea fluxurilor concentrate de energie electrică la trecerea descărcărilor electrice prin impulsuri în mediul gazos şi transferul polar al materialului anodului pe suprafaţa catodului. În urma interacţiunii fazelor lichide ale materialului anodului şi catodului în straturile superficiale se formează o serie de compuşi chimici, proprietăţile cărora se pot pronostica. Pe baza introducerii componenţilor corespunzători de aliere se pot obţine aliaje cu o înaltă rezistenţă la coroziune [1]. A process of electric spark alloying of metal surfaces is known, effective in modifying the chemical composition and properties of the surface layers of metallic materials, based on the use of concentrated flows of electric energy when passing pulsed electric discharges in the gaseous medium and the polar transfer of the anode material to the cathode surface. As a result of the interaction of the liquid phases of the anode and cathode materials in the surface layers, a series of chemical compounds are formed, the properties of which can be predicted. Based on the introduction of appropriate alloying components, alloys with high corrosion resistance can be obtained [1].
Dezavantajele acestui procedeu sunt rugozitatea relativ înaltă şi discontinuitatea acoperirii, existenţa distribuţiei neuniforme a unor sectoare active ale suprafeţei modificate. The disadvantages of this process are the relatively high roughness and discontinuity of the coating, the existence of non-uniform distribution of active sectors of the modified surface.
În calitate de cea mai apropiată soluţie serveşte procedeul de mărire a rezistenţei la coroziune a oţelului care constă în aceea că piesa din oţel mai întâi se supune alierii cu scântei electrice cu un metal rezistent la coroziune, cu timpul specific de aliere de 1 min/cm2, la un regim cu energia descărcării electrice în diapazonul 0,3…4,0 J. Apoi se efectuează tratamentul, care constă în încălzirea anodică a piesei timp de 30 s într-un electrolit, ce conţine compuşi azotici NH4Cl 100 g/l şi NH4OH 50 g/l sau NH4Cl 110 g/l şi NaNO3 110 g/l, până la temperatura de 750°C, la tensiunea dintre electrozi de 150…220 V, cu densitatea curentului electric de 1…15 A/cm2, şi răcirea ulterioară a piesei la aer [2]. The closest solution is the process of increasing the corrosion resistance of steel, which consists in the fact that the steel part is first subjected to electric spark alloying with a corrosion-resistant metal, with a specific alloying time of 1 min/cm2, at a regime with an electric discharge energy in the range of 0.3…4.0 J. Then the treatment is performed, which consists of anodic heating of the part for 30 s in an electrolyte containing nitrogen compounds NH4Cl 100 g/l and NH4OH 50 g/l or NH4Cl 110 g/l and NaNO3 110 g/l, up to a temperature of 750°C, at a voltage between the electrodes of 150…220 V, with an electric current density of 1…15 A/cm2, and subsequent cooling of the part in air [2].
Dezavantajele acestui procedeu constau în aceea că tratamentul termochimic nu influenţează continuitatea acoperirii, ca rezultat al tratamentului în pori se formează numai stratul de nitrură, rezistenţa la coroziune a căruia ar putea fi insuficientă într-un şir de medii agresive, ceea ce duce la corodarea acoperirii, îndepărtarea produselor coroziunii şi, astfel, la deteriorarea piesei. The disadvantages of this process are that the thermochemical treatment does not influence the continuity of the coating, as a result of the treatment in the pores only the nitride layer is formed, the corrosion resistance of which could be insufficient in a number of aggressive environments, which leads to corrosion of the coating, removal of corrosion products and, thus, damage to the part.
Problema pe care o rezolvă invenţia constă în elaborarea unui procedeu de mărire a rezistenţei la coroziune a oţelului supus alierii prin scântei electrice, care asigură rezistenţa necesară la coroziune a metalului în pori. The problem solved by the invention consists in developing a process for increasing the corrosion resistance of steel subjected to electric spark alloying, which ensures the necessary corrosion resistance of the metal in the pores.
Problema se soluţionează prin aceea că procedeul de tratament anticoroziv al oţelului, conform invenţiei, constă în alierea prin scântei electrice a suprafeţei piesei din oţel strat cu strat cu durata impulsurilor de 10…2500 µs şi frecvenţa de 1500…25 Hz corespunzător, cu obţinerea unei acoperiri. Apoi se efectuează tratamentul termochimic anodic al acoperirii obţinute timp de 1…5 min într-un electrolit ce conţine compuşi anorganici ai azotului cu un adaos de 0,5…15 g/l de tanin la tensiunea dintre electrozi de 150…220 V, densitatea curentului de 1…20 A/cm2 şi temperatura anodului de 600…900°C cu călirea-oxidarea ulterioară în electrolit. După aceasta piesa se menţine timp de 3…5 ore în acid ortofosforic concentrat şi/sau într-o soluţie de nitrit de sodiu cu concentraţia de 30…150 g/l la temperatura de 70…100°C, apoi piesa se spală, se usucă şi porii acoperirii se umplu electrolitic cu material izolant. The problem is solved by the fact that the anti-corrosion treatment process of steel, according to the invention, consists in the alloying by electric sparks of the surface of the steel part layer by layer with the pulse duration of 10…2500 µs and the frequency of 1500…25 Hz correspondingly, with the obtaining of a coating. Then the anodic thermochemical treatment of the obtained coating is carried out for 1…5 min in an electrolyte containing inorganic nitrogen compounds with an addition of 0.5…15 g/l of tannin at the voltage between the electrodes of 150…220 V, the current density of 1…20 A/cm2 and the anode temperature of 600…900°C with subsequent quenching-oxidation in the electrolyte. After this, the piece is kept for 3…5 hours in concentrated orthophosphoric acid and/or in a sodium nitrite solution with a concentration of 30…150 g/l at a temperature of 70…100°C, then the piece is washed, dried and the pores of the coating are electrolytically filled with insulating material.
Rezultatul tehnic al aplicării procedeului constă în mărirea rezistenţei la coroziune a pieselor datorită pasivizării metalului de bază în pori şi formarea în pori a unui strat de nitruri şi tanaţi care permite de a evita corodarea acoperirii rezistente la coroziune şi uzură depuse prin alierea cu scântei electrice şi exfolierea ei. The technical result of applying the process consists in increasing the corrosion resistance of the parts due to the passivation of the base metal in the pores and the formation in the pores of a layer of nitrides and tannates that allows to avoid corroding the corrosion and wear-resistant coating deposited by electric spark alloying and its exfoliation.
Exemplu de realizare a invenţiei Example of embodiment of the invention
Încercările au fost efectuate în modul următor. Mostrele au fost confecţionate din oţel CT.3 (componenţa, % de masă: C - 0,14…0,22, Mn - 0,40…0,65, Si - 0,12…0,30, restul - Fe), în formă de placă cu suprafaţa de 2 cm2. The tests were performed as follows. The samples were made of CT.3 steel (composition, mass %: C - 0.14…0.22, Mn - 0.40…0.65, Si - 0.12…0.30, the rest - Fe), in the form of a plate with a surface area of 2 cm2.
Alierea mostrelor a fost efectuată cu aliaj BK8 (componenţa, % de masă: WC - 92, Co - 8). The alloying of the samples was performed with BK8 alloy (composition, mass %: WC - 92, Co - 8).
Grosimea stratului aplicat a constituit 0,2…0,4 mm. Procesul de depunere a fost realizat în trei etape. La prima etapă prelucrarea a fost efectuată la regimuri fine, durata impulsului de 30 µs şi frecvenţa de 1200…1500 Hz. Ca rezultat, s-a obţinut o acoperire cu grosimea de 0,1…0,15 mm, cu rugozitate joasă şi un număr mic de pori. La a doua etapă prelucrarea s-a efectuat la regimuri mai dure (regim grosier), durata impulsului fiind de 1000 µs şi frecvenţa de 50…100 Hz. S-au obţinut acoperiri cu grosimea de 0,15…0,2 mm. La cea de-a treia etapă prelucrarea a fost efectuată din nou la un regim fin, durata impulsului de 30…40 µs şi frecvenţa de 1200…1500 Hz. În acelaşi timp, acoperirile aplicate anterior s-au netezit, devenind mai omogene şi continue. The thickness of the applied layer was 0.2…0.4 mm. The deposition process was carried out in three stages. At the first stage, the processing was carried out at fine modes, the pulse duration was 30 µs and the frequency was 1200…1500 Hz. As a result, a coating with a thickness of 0.1…0.15 mm was obtained, with low roughness and a small number of pores. At the second stage, the processing was carried out at harder modes (coarse mode), the pulse duration was 1000 µs and the frequency was 50…100 Hz. Coatings with a thickness of 0.15…0.2 mm were obtained. At the third stage, the processing was again carried out at a fine regime, the pulse duration was 30…40 µs and the frequency was 1200…1500 Hz. At the same time, the previously applied coatings were smoothed, becoming more homogeneous and continuous.
Este de menţionat că pentru aplicarea straturilor mai groase de o calitate bună este necesar de a efectua alierea prin scântei electrice a suprafeţei strat cu strat, alternând regimurile fine şi dure. It is worth mentioning that to apply thicker layers of good quality, it is necessary to perform electric spark alloying of the surface layer by layer, alternating fine and hard regimes.
Tratamentul termochimic anodic al mostrelor a fost efectuat într-un electrolit care conţine, g/l: NH4Cl - 110 şi NaNO3 - 110, cu un adaos de 10 g/l de tanin, la tensiunea de 200 V la electrozi, densitatea curentului de 2 A/cm2, temperatura anodului de 750°C, timp de 3 min, urmat de călirea-oxidarea în electrolit. The anodic thermochemical treatment of the samples was performed in an electrolyte containing, g/l: NH4Cl - 110 and NaNO3 - 110, with an addition of 10 g/l of tannin, at a voltage of 200 V at the electrodes, a current density of 2 A/cm2, an anode temperature of 750°C, for 3 min, followed by quenching-oxidation in the electrolyte.
Apoi mostrele au fost spălate cu apă şi introduse în acid ortofosforic concentrat pentru 4 ore şi într-o soluţie de nitrit de sodiu NaNO2 cu concentraţia de 50 g/l la temperatura de 70°C. Then the samples were washed with water and placed in concentrated orthophosphoric acid for 4 hours and in a solution of sodium nitrite NaNO2 with a concentration of 50 g/l at a temperature of 70°C.
Pentru comparaţie, mostrele din oţel neprelucrat au fost supuse unui tratament cu acid ortofosforic concentrat sau într-o soluţie de nitrit de sodiu cu concentraţia de 50 g/l, sau într-o soluţie de acid sulfuric de 48% timp de 4 ore. For comparison, raw steel samples were subjected to treatment with concentrated orthophosphoric acid or in a sodium nitrite solution with a concentration of 50 g/l, or in a 48% sulfuric acid solution for 4 hours.
Mostrele aliate cu aliajul BK8 şi supuse tratamentului termochimic după pasivizare au fost spălate în apă fierbinte şi plasate în calitate de catod într-o baie cu soluţie de electrolit apos de email В-ФЛ-1199 Э, cu concentraţia de 4% la pH 7,4. Procesul de depunere s-a efectuat la o tensiune de 40 V la electrozi şi o durată de 100 s. Acoperirea obţinută a fost fixată la 180°C timp de 30 min. The samples alloyed with the BK8 alloy and subjected to thermochemical treatment after passivation were washed in hot water and placed as a cathode in a bath with an aqueous electrolyte solution of enamel В-ФЛ-1199 Э, with a concentration of 4% at pH 7.4. The deposition process was carried out at a voltage of 40 V at the electrodes and a duration of 100 s. The obtained coating was fixed at 180°C for 30 min.
Pentru a confirma faptul că aplicarea procedeului rezolvă problema propusă, au fost efectuate încercări comparative, rezultatele cărora sunt prezentate în tabel. Rezistenţa mostrelor a fost determinată prin valoarea intensităţii curentului de dizolvare anodică la testări în soluţia apoasă ce conţine, g/l: NaCl - 7,0 şi Na2SO4 (anhidru) - 7,0 pentru diferite valori ale potenţialelor anodice. To confirm that the application of the procedure solves the proposed problem, comparative tests were performed, the results of which are presented in the table. The resistance of the samples was determined by the value of the intensity of the anodic dissolution current when tested in the aqueous solution containing, g/l: NaCl - 7.0 and Na2SO4 (anhydrous) - 7.0 for different values of the anodic potentials.
Tabel Table
Influenţa tipului de prelucrare asupra intensităţii curentului de dizolvare anodică Influence of processing type on anodic dissolution current intensity
Tipul procedeului de prelucrare Ia, mA la φ=0 V Ia, mA la φ=0,4 V Ia, mA la φ=1,2 V Oţel neprelucrat 560,0 600,0 640,0 Oţel pasivizat în H2SO4 21,2 110,0 - Oţel pasivizat în NaNO2 8,1 52,0 136,5 Oţel pasivizat în H3PO4 0,0 0,0 3,5 Oţel supus tratamentului termochimic 25,6 38,5 69,4 Oţel aliat cu BK8 21,4 42,5 61,5 Oţel aliat cu BK8 şi pasivizat în H3PO4 8,3 14,2 24,4 Oţel aliat cu BK8 şi pasivizat în NaNO2 7,3 24,5 46,0 Oţel aliat cu BK8 şi supus tratamentului termochimic 12,4 20,1 29,2 Oţel aliat cu BK8, supus tratamentului termochimic şi pasivizat în H3PO4 5,4 10,6 15,3 Oţel aliat cu BK8, supus tratamentului termochimic şi pasivizat în H3PO4 şi NaNO2 4,2 7,5 10,1 Oţel aliat cu BK8, supus tratamentului termochimic şi pasivizat în H3PO4, cu umplerea electrolitică a porilor 2,0 3,5 5,3Type of processing process Ia, mA at φ=0 V Ia, mA at φ=0.4 V Ia, mA at φ=1.2 V Raw steel 560.0 600.0 640.0 Steel passivated in H2SO4 21.2 110.0 - Steel passivated in NaNO2 8.1 52.0 136.5 Steel passivated in H3PO4 0.0 0.0 3.5 Steel subjected to thermochemical treatment 25.6 38.5 69.4 Steel alloyed with BK8 21.4 42.5 61.5 Steel alloyed with BK8 and passivated in H3PO4 8.3 14.2 24.4 Steel alloyed with BK8 and passivated in NaNO2 7.3 24.5 46.0 Steel alloyed with BK8 and subjected to thermochemical treatment 12.4 20.1 29.2 Steel alloyed with BK8, subjected to thermochemical treatment and passivated in H3PO4 5.4 10.6 15.3 Steel alloyed with BK8, subjected to thermochemical treatment and passivated in H3PO4 and NaNO2 4.2 7.5 10.1 Steel alloyed with BK8, subjected to thermochemical treatment and passivated in H3PO4, with electrolytic pore filling 2.0 3.5 5.3
Din datele prezentate în tabel este clar că pasivizarea mostrei din CT. 3 în acid sulfuric reduce intensitatea curentului de dizolvare anodică de 5,45…26,4 ori. Pasivizarea oţelului în nitrit de sodiu (NaNO2) reduce şi mai mult intensitatea - de 4,7…69,1 ori. Pasivizarea oţelului în acid ortofosforic reduce la maxim coroziunea, la potenţialele 0,0 şi 0,4 V suprafaţa este pasivizată complet şi curentul lipseşte, iar la un potenţial de 1,2 V intensitatea curentului de dizolvare anodică se diminuează de 182,9 ori comparativ cu oţelul neprelucrat. Cu toate acestea, pelicula de protecţie care acoperă întreaga suprafaţă a mostrei cu timpul se perforează şi pe ea apar focare separate ale coroziunii. From the data presented in the table it is clear that passivation of the sample from CT. 3 in sulfuric acid reduces the intensity of the anodic dissolution current by 5.45…26.4 times. Passivation of steel in sodium nitrite (NaNO2) reduces the intensity even more - by 4.7…69.1 times. Passivation of steel in orthophosphoric acid reduces corrosion to the maximum, at potentials of 0.0 and 0.4 V the surface is completely passivated and the current is absent, and at a potential of 1.2 V the intensity of the anodic dissolution current decreases by 182.9 times compared to unprocessed steel. However, the protective film covering the entire surface of the sample over time is perforated and separate foci of corrosion appear on it.
În cazul tratamentului termochimic al mostrei din oţel intensitatea curentului de dizolvare anodică scade de 9,2…21,9 ori datorită formării pe suprafaţă a stratului de nitrură rezistent la coroziune, pe care este format tanatul de fier. In the case of thermochemical treatment of the steel sample, the intensity of the anodic dissolution current decreases by 9.2…21.9 times due to the formation of a corrosion-resistant nitride layer on the surface, on which iron tannate is formed.
Pe suprafaţa mostrei din oţel aliată cu aliaj dur BK8, prin impulsuri cu parametrii menţionaţi, se formează o acoperire rezistentă la uzură cu rugozitate scăzută care conţine un număr mai mic de pori decât acoperirile obţinute prin tehnologia obişnuită. Aceasta duce la diminuarea intensităţii curentului de dizolvare anodică de 10,4…26,2 ori în comparaţie cu oţelul neprelucrat, deoarece prin pori ionii agresivi de C1- şi SO4 2- pătrund într-o măsură mai mică în substratul de oţel şi îl corodează nesemnificativ. On the surface of the steel sample alloyed with hard alloy BK8, by pulses with the mentioned parameters, a wear-resistant coating with low roughness is formed, which contains a smaller number of pores than coatings obtained by conventional technology. This leads to a decrease in the intensity of the anodic dissolution current by 10.4…26.2 times compared to untreated steel, since through the pores the aggressive ions of C1- and SO4 2- penetrate to a lesser extent into the steel substrate and corrode it insignificantly.
În cazul alierii suprafeţei mostrei cu aliajul BK8 şi pasivizării ulterioare a acoperirii obţinute în acid ortofosforic concentrat intensitatea curentului de dizolvare anodică este mai mică de 2,5…3,0 ori comparativ cu oţelul doar aliat, datorită pasivizării piesei în porii existenţi. Un efect puţin mai mic, de 1,3…2,9 ori, se observă la pasivizarea suprafeţei aliate în nitrit de sodiu. Dacă supunem tratamentului termochimic mostra din oţel aliat cu BK8, atunci în comparaţie cu suprafaţa aliată, intensitatea curentului de dizolvare anodică se diminuează de 1,7…2,1 ori, datorită formării în pori a unui strat de nitrură concomitent cu tanaţii. În cazul alierii oţelului cu tratamentul termochimic ulterior şi pasivizării în acid ortofosforic intensitatea curentului de dizolvare anodică se diminuează de 4 ori în comparaţie cu oţelul supus doar alierii. In the case of alloying the sample surface with the BK8 alloy and subsequent passivation of the coating obtained in concentrated orthophosphoric acid, the intensity of the anodic dissolution current is 2.5…3.0 times lower compared to the steel only alloyed, due to the passivation of the part in the existing pores. A slightly smaller effect, 1.3…2.9 times, is observed when passivating the alloyed surface in sodium nitrite. If we subject the sample of steel alloyed with BK8 to thermochemical treatment, then in comparison with the alloyed surface, the intensity of the anodic dissolution current decreases by 1.7…2.1 times, due to the formation of a nitride layer in the pores simultaneously with tannates. In the case of alloying the steel with subsequent thermochemical treatment and passivation in orthophosphoric acid, the intensity of the anodic dissolution current decreases by 4 times compared to the steel subjected to only alloying.
Cu toate acestea, cel mai mare efect pozitiv se observă la tratamentul combinat, alierea cu BK8, tratamentul termochimic şi pasivizarea în acid ortofosforic, urmată de umplerea electrolitică a porilor. În acest caz, intensitatea curentului de dizolvare anodică în comparaţie cu suprafaţa neprelucrată a oţelului scade de 120…280 de ori, în comparaţie cu suprafaţa doar aliată - de 10,7…12,1 ori, iar în comparaţie cu suprafaţa supusă alierii, tratamentului termochimic şi pasivizării în acid ortofosforic - de 2,7…3,0 ori. However, the greatest positive effect is observed with the combined treatment, alloying with BK8, thermochemical treatment and passivation in orthophosphoric acid, followed by electrolytic filling of the pores. In this case, the intensity of the anodic dissolution current in comparison with the unprocessed steel surface decreases by 120…280 times, in comparison with the only alloyed surface - by 10.7…12.1 times, and in comparison with the surface subjected to alloying, thermochemical treatment and passivation in orthophosphoric acid - by 2.7…3.0 times.
Astfel, procedeul elaborat permite mărirea semnificativă a rezistenţei la coroziune a acoperirilor obţinute prin aliere cu scântei electrice datorită măririi continuităţii lor şi diminuării considerabile a coroziunii porilor existenţi. Thus, the developed process allows for a significant increase in the corrosion resistance of coatings obtained by electric spark alloying due to the increase in their continuity and the considerable reduction in corrosion of existing pores.
1. Томашов Н., Чернова Г. Теория коррозии и коррозионностойкие конструкционные сплавы. Москва, Металлургия, 1986, с. 329 1. Томашов Н., Чернова Г. Corrosion theory and corrosion-resistant structural alloys. Moscow, Metallurgy, 1986, p. 329
2. MD 3708 F1 2008.09.30 2. MD 3708 F1 2008.09.30
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| MD3708F1 (en) * | 2007-05-23 | 2008-09-30 | Institutul De Fizica Aplicata Al Academiei De Stiinte A Moldovei | Process for enhancing the corrosion resistance of steel |
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