Effects of blackening parameters on the formation and adhesion of oxide on AISI 4140 steel

Chandra-ambhorn, Somrerk; Srihirun, Sermsak; Siripongsakul, Thamrongsin

doi:10.1108/acmm-12-2017-1877

Cited by 2 publications

(1 citation statement)

References 14 publications

(17 reference statements)

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“…The obvious disadvantages of the alkaline oxidation process are high energy consumption, difficult working conditions and aggressiveness of the solutions used. In addition, coatings formed in alkaline solutions are highly porous and therefore can be used as protective coatings only in light climatic conditions [1,2].…”

Section: Introductionmentioning

confidence: 99%

Low-temperature deposition process for black phosphate-selenide coatings

Aleshina¹,

Abrashov²,

Grigoryan³

et al. 2021

cisisr

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Oxide coatings are widely used as protective and decorative coatings on ferrous metals under non-harsh operating conditions. For protective and decorative oxidation, a chemical oxidation method is widely used using concentrated alkaline solutions (600-800 g/l NaOH) operating at very high temperatures (130-150 °C). The obvious disadvantages of the process are the high energy consumption, difficult working conditions, the aggressiveness of the solutions used and low protective ability of the coatings due to their high porosity. In addition, it is known that to harden the surfaces of machine parts in order to increase wear resistance, they are thermally laser treated. The surface hardening is the more effective, the higher the absorption coefficient of the treated surface. For laser heat treatment, high-temperature (95-98 °C) processes of applying black phosphate coatings with a high absorption coefficient (0.8-0.9) are used. The disadvantages of these processes are also the instability of solutions and the irreproducibility of the results. This work is about to the study of the process of formation of phosphate-selenide coatings on steel in order to replace high-temperature solutions of black oxidation and phosphating. A low-temperature process has been developed for the deposition of black selenide-containing phosphate coatings on steel, corresponding to a point of 10 on a ten-point color scale, in a solution containing: 4-8 g/l Na 2 SeO 3 ; 1-4 g/l CuSO 4 ⋅5H 2 O; 0.5-5 g/l NaH 2 PO 4 and 0.25-2.5 g/l Na 2 HPO 4 ([NaH 2 PO 4 ]/[Na 2 HPO 4 ] molar ratio is 2); 5 min at pH = 2-3, t = 18-25 °C. Oiling the coatings in I-20A industrial oil for 2 min leads to an increase in the protective ability of the coatings according to Akimov from 1 to 25 min. Corrosion tests of coatings in a salt spray chamber in accordance with ASTM B117 have shown that oiled phosphate-selenide coatings have the greatest protective ability: the first spots of red corrosion appear after 20 hours of testing, while oxidized, oiled samples begin to corrode after 18 hours. After 100 hours of testing, the area of the oxidized sample affected by corrosion is 90 %, and the oiled phosphated sample is 50.

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Section: Introductionmentioning

confidence: 99%

Low-temperature deposition process for black phosphate-selenide coatings

Aleshina¹,

Abrashov²,

Grigoryan³

et al. 2021

cisisr

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Hydrothermal blackening on AISI 4140 steel with and without hydrazine hydrate

Wiman

Doungkaew

Siripongsakul

2021

IOP Conf. Ser.: Mater. Sci. Eng.

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The blackening coating is a conversion coating with the black colour of crystallised magnetite (Fe 3O4) on the surface of steel. The coating is to be soaked with oil or wax to prevent the corrosive environment. Recently, the technique to synthesise the black coating, hydrothermal method is introduced. In the synthesis process, hydrazine hydrate (N2H4·H2O) is often recommended as a catalyst but it is also reported toxicity. In this work, AISI 4140 was hydrothermally immersed in the FeSO4·7H2O added NaOH solution with and without addition of hydrazine hydrate. During the process, the temperature and pressure of the chamber were controlled at 140°C and 2 bar, respectively. To confirm the formation of Fe 3O4, the samples were characterised by SEM and XRD. These results showed that the coatings were composed of octahedron morphology in all conditions and the thicknesses of the coating with hydrazine hydrate concentration of 0.0, 0.1, and 0.5M were 7.05, 9.25, and 8.75 μm, respectively. With hydrazine hydrate, the Fe3O4 layer can be easily formed. However, the results of the oxalic acid spot test and potentiodynamic polarisation indicated the equivalence in quality of the coating, despite the absence of hydrazine hydrate.

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Effects of blackening parameters on the formation and adhesion of oxide on AISI 4140 steel

Cited by 2 publications

References 14 publications

Low-temperature deposition process for black phosphate-selenide coatings

Low-temperature deposition process for black phosphate-selenide coatings

Hydrothermal blackening on AISI 4140 steel with and without hydrazine hydrate

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