مطالعه اثر همزمان عملیات ساچمه‌زنی و پخت بر رفتار کششی فولاد آلیاژی 50CrV4

محورهای موضوعی : عملیات حرارتی

ملیحه قاسم زاده ¹ , حمید ناظمی ²

1 - استادیار، گروه مهندسی مواد، مرکز نظرآباد، واحد کرج، دانشگاه آزاد اسلامی، کرج، ایران.
2 - استادیار، گروه مهندسی مکانیک و مواد، واحد مبارکه، دانشگاه آزاد اسلامی، مبارکه، ایران.

تاریخ دریافت : 1400/01/08 تاریخ پذیرش : 1400/02/23 تاریخ انتشار : 1400/12/01

کلید واژه: تردی هیدروژنی, فولاد 50CrV4, پخت, ساچمه‌زنی,

چکیده مقاله :

در این مقاله قطعاتی از مفتول فولاد 50CrV4 بـه قطر mm4 تحت آبکـاری الکتریکی Zn خالص قرار گرفت. اثر عملیات ساچمه زنی قبل از آبکاری و عملیات پخت بعد از آبکاری الکتریکی در عملکرد کششی فولاد بررسی شد. ساچمه زنی قبل از آبکاری به مدت 20 دقیقه با ساچمه هایی به قطر mm5/0 و سختی RC58 انجام شد. عملیات پخت بعد از آبکاری به مدت 24 ساعت در دمای °C200 انجام شد. سپس در نهایت نمونه ها تحت آزمون‌های کشش با نرخ کرنش آهسته، سختی سنجی و تصویربرداری SEM قرار گرفتند. نتایج نشان داد که اثر عملیات پخت در بهبود عمر مکانیکی نمونه تحت کشش به تنهایی بیشتر از عملیات ساچمه زنی است. متوسط زمان تا شکست نمونه های آبکاری شده و پخت شده 5/2 ساعت ولی متوسط زمان شکست برای نمونه های ساچمه زنی شده و آبکاری شده 1/2 ساعت به دست آمد. اثر هم زمان عملیات ساچمه زنی قبل از آبکاری و پخت بعد از آبکاری منجر به بهبود بیشتر عملکرد کششی مفتول و رسیدن زمان متوسط شکست به 05/3 ساعت در آزمون نرخ کرنش آهسته شد. در این شرایط اندیس حساسیت به تردی از 76/0 بـرای نمونه هـای فقط آبکاری شده به 13/0 برای نمونه های ساچمه زنی و پخت شده کاهش یافت که بهبود بسیار خوبی را نشان می دهد. اثر ساچمه زنی بر خواص کششی فولاد را می‌توان به ایجاد یک لایه تنش فشاری پسماند در سطح زیر لایه نسبت داد که منجر به کاهش نرخ رشد ریزترک‌های ناشی از تنش‌های کششی در شرایط کاری می‌شود. همچنین نتایج نشان داد که در اثر عملیات پخت ترک‌های ریز و پیوسته‌ای در فصل مشترک پوشش / زیر لایه ایجاد می‌شود که مسیرهای مناسبی را برای خروج هیدروژن از زیر لایه فراهم می‌کنند.

چکیده انگلیسی:

In this paper, 50CrV4 steel wire with a diameter of 4 mm were subjected to pure Zn electroplating. The effect of shot peening before and baking after electroplating on tensile performance of steel was investigated. Bombardment was done before plating for 20 minutes with shots 0.5 mm and 58 RC. Baking was performeIn this paper, 50CrV4 steel wire with a diameter of 4 mm were subjected to pure Zn electroplating. The effect of shot peening before and baking after electroplating on tensile performance of steel was investigated. Bombardment was done before plating for 20 minutes with shots 0.5 mm and 58 RC. Baking was performed after plating for 24 hours at 200°C. Finally, the samples were subjected to slow strain rate test, microhardness test and SEM imaging. The results showed that the effect of baking on improving the mechanical life of the sample under tension alone is greater than the shot peening. The mean time to failure of plated and baked samples was 2.5 hours, but for shot and plated samples was 2.1 hours. The simultaneous effect of pre-plating shot peening and post-plating baking led to further improvement of the tensile performance of the wire and the mean failure time reached 3.55 hours in the slow strain rate test. The embrittlement susceptibility index is now reduced from 0.76 for only plated samples to 0.13 for shot peened and baked samples, which shows a very good improvement. The effect of shot peening on the tensile properties of steel can be attributed to the formation of a residual compressive stress layer on the substrate surface, which leads to a reduction in the growth rate of microcracks due to tensile stresses under working conditions. The results also showed that due to the baking, continuous microcracks are created in the coating / substrate interface, which provide suitable paths for hydrogen to leave the substrate. after plating for 24 hours at 200°C. Finally, the samples were subjected to slow strain rate test, microhardness test and SEM imaging. The results showed that the effect of baking on improving the mechanical life of the sample under tension alone is greater than the shot peening. The mean time to failure of plated and baked samples was 2.5 hours, but for shot and plated samples was 2.1 hours. The simultaneous effect of pre-plating shot peening and post-plating baking led to further improvement of the tensile performance of the wire and the mean failure time reached 3.55 hours in the slow strain rate test. The embrittlement susceptibility index is now reduced from 0.76 for only plated samples to 0.13 for shot peened and baked samples, which shows a very good improvement. The effect of shot peening on the tensile properties of steel can be attributed to the formation of a residual compressive stress layer on the substrate surface, which leads to a reduction in the growth rate of microcracks due to tensile stresses under working conditions.

منابع و مأخذ:

• F. Timmins, "Solutions to hydrogen attack in steels". First printing: ASM International Pub, 1997.

 

• Vehoff, "Hydrogen in metals III". Berlin/ Heidelberg: Springer. pp. 215–278, 1997.

 

• Dan, "Fundamentals of spring design". Pub. Spring Manufacturers Institute (SMI). pp.1-12, 2000.

 

• P. Hayes, "Spring failure appearances, mechanism and diagnoses". SRAMA. Report no. 464, 1994.


• SRAMA Group, "Spring material selector". Second edition; SRAMA Pub, 1991.

 

• J. Lee, J. H. Park, D. H. Lee & S. S. Kang, "Effect of heat treatment on the hydrogen delayed fracture of high strength spring steel". Journal of Mechanical Science and Technology, vol. 27, no. 10, pp. 2991-2996, 2013.

 

• British Standards. :Standard No. BS 1706-1990".

 

• San Marchi, B. P. Somerday & S. L. Robinson, "Permeability, solubility and diffusivity of hydrogen isotopes in stainless steels at high gas pressures". International Journal of Hydrogen Energy, vol, 32, pp. 100-116, 2007.

 

• Figueroa & M. J. Robinson, "The effects of sacrificial coatings on hydrogen embrittlement and re-embrittlement of ultra high strength steels". Corrosion Science, vol. 50, pp.1066-1079, 2008.

 

• M. K. Hillier & M. J. Robinson, "Hydrogen embrittlement of high strength steel electroplated with zinc-cobalt alloys", Corrosion Science, vol. 46, pp. 715-727, 2004.

 

• M. K. Hillier & M. J. Robinson, "Permeation measurements to study hydrogen uptake by steel electroplated with zinc-cobalt alloys". Corrosion Science, vol. 48, pp.1019-1035, 2006.

 

• Wandell, "Shot peening: an answer to hydrogen embrittlement?". Springs journal, vol. 34, no. 1, pp. 31-39, 1995.

 

• European Standard EN 10002-1. "Metallic materials – tensile testing".

 

• Peugeot Standard System, Standard No. B151240, "Mechanical treatment: shot peening".

 

• ASM, "Metals Hand Book", Ninth Edition. 5, 1990.

 

• ASTM Standards, ASTM B850-98, "Standard guide for post-coating treatment of steel for reducing risk of hydrogen embrittlement".

 

• ASTM Standards, ASTM E384, "Standard Test Method for Microindentation Hardness of Materials".

 

• El hajjami, M. P. Gigandet, M. De Petris-Wery, J. C. Catonne, J. J. Duprat & L. Thiery, "Hydrogen permeation inhibition by zinc–nickel alloy plating on steel XC68". Applied Surface Science, vol. 255, pp. 1654-1660, 2008.

 

• P. Nascimento, M. A. S. Torres, R. C. Souza & Voorwald, H. J. C., (2002). "Effect of a shot peening pre treatment on the fatigue behaviour of hard chromium on electroless nickel interlayer coated AISI 4340 aeronautical steel", Materials Research, vol. 5, no. 2, pp. 95-100.

 

• Bories, J. P. Bonino & A. Rousset, "Structure and thermal stability of zinc–nickel electrodeposits". Journal of Applied Electrochemistry, vol. 29, 1045-1051, 1999.

 

• W. Siitari, M. Sagiyama & T. Hara, "Corrosion of Ni-Zn electrodeposited alloy". Transactions ISIJ, vol. 23, pp. 959-966, 1983.

 

• Lin, H. Lee & S. Hsieh, "Microcracking of flash coatings and its effect on the Zn-Ni coating adhesion of electrodeposited sheet steel". Metallurgical and Materials Transactions A, vol. 30, pp. 437-448, 1999.

 

• Brahimi & S. Yue, "Effect of surface processing variables and coating characteristics on hydrogen embrittlement of steel fasteners Part2: Electroplating and non electrolytic processes". SUR/FIN 2009. Technical Conference; NASF (National Association for Surface Finishing), 2009.