Failure Analysis of NbVC Coating Formation onto AISI D2 Tool Steel during Thermo Reactive Diffusion by Pack Method

Khamda, Izdada Rotaal (2019) Failure Analysis of NbVC Coating Formation onto AISI D2 Tool Steel during Thermo Reactive Diffusion by Pack Method. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Threads of metal fasteners can be created by thread rolling process using specific thread dies. Thread rolling is a cold forging process that can be carried out on ductile metal. The quality of the thread rolling die is determined by their wear-resistant properties and hardness number of the material. In order to increase the hardness and the wear resistance of the dies, surface treatment can be applied. One of the process that can be applied is thermo-reactive diffusion (TRD) technique due to its simplicity, low in cost, and environment friendly. TRD technique can produce super hard layers of carbide, nitride or carbonitride with the main elements vanadium, niobium, tantalum, chromium, molybdenum or tungsten. The carbon or nitrogen in the steel will diffuse by carbide-forming or nitride-forming elements. The diffused carbon-forming element (CFE) or nitride-forming element (NFE) in the deposited coating to form a dense and bonded carbide or nitride coating at the substrate surface. This research will explore the effect of temperature variation of TRD process onto vanadium-niobium coating formation on the surface of AISI D2. The TRD process is carried out by powder-pack method in a sealed steel container containing powder mixture of niobium and vanadium as master alloy, alumina (Al2O3) as inert filler and ammonium chloride (NH4Cl) as activator. The samples were covered with powder mixture and then heated in the electric resistance furnace at temperature of 950, 1000 and 1050 ˚C for 6 hours. Upon finishing the process, the sample is allowed to cool in the open air. The coating cross section was analyzed using optical microscope. The hardness measurement also performed on the same sample. XRD was utilized to investigate the coating chemical composition. The wear of the coatings are assessed using revolving tribological test under dry sliding condition. The microstructure, hardness, chemical composition and wear properties of treated and untreated AISI D2 substrate were studied. The XRD and microstructure test results did not find any niobium-vanadium carbide coating on AISI D2 substrate. In untreated specimens found chromium carbide (Cr7C3), so there is no sufficient supply of carbon to form niobium-vanadium carbide when the thermo reactive diffusion process takes place. In addition, the chromium carbide (Cr7C3) has the lowest free energy of formation compared to NbC and VC. So that the carbide formed only on the substrate does not form a coating. Untreated specimen has hardness number of 277.8 HV. After TRD treatment, the hardness number is increase. For heating temperature variation of 950°C, 1000°C, and 1050°C have hardness number of 798.21HV, 787.3HV, 774.2HV respectively. The value of hardness rises due to the hardening of the AISI D2 specimen. The highest wear resistance owned by temperature variation of 950°C and the lowest wear resistance owned by the untreated specimen. ================================================================================================ Thread dari fastener logam dapat dibuat dengan proses thread rolling menggunakan thread dies yang spesifik. Threading adalah proses penempaan dingin yang dapat dilakukan pada logam ulet. Kualitas cetakan ulir ditentukan oleh sifat tahan aus dan nilai kekerasan material. Untuk meningkatkan kekerasan dan ketahanan aus pada cetakan, perawatan permukaan dapat diterapkan. Salah satu proses yang dapat diterapkan adalah teknik thermo reactive diffusion (TRD) karena kesederhanaannya, murah, dan ramah lingkungan. Teknik TRD dapat menghasilkan lapisan super keras karbida, nitrida atau karbonitrida dengan elemen utama vanadium, niobium, tantalum, kromium, molibdenum atau tungsten. Karbon atau nitrogen dalam baja akan berdifusi oleh unsur pembentuk karbida atau pembentuk nitrida. Elemen pembentuk karbon terdifusi (CFE) atau elemen pembentuk nitrida (NFE) dalam lapisan yang diendapkan untuk membentuk lapisan karbida atau nitrida yang padat dan terikat pada permukaan substrat. Penelitian ini akan mengeksplorasi pengaruh variasi suhu proses TRD terhadap pembentukan lapisan vanadium-niobium pada permukaan AISI D2. Proses TRD dilakukan dengan metode powder pack dalam wadah baja tertutup yang mengandung campuran bubuk niobium dan vanadium sebagai paduan utama, alumina (Al2O3) sebagai pengisi dan amonium klorida (NH4Cl) sebagai aktivator. Sampel ditutup dengan campuran bubuk dan kemudian dipanaskan dalam tungku tahanan listrik pada suhu 950, 1000 dan 1050 ˚C selama 6 jam. Setelah menyelesaikan proses TRD, sampel dibiarkan dingin di udara terbuka. Penampang melintang dianalisis dengan menggunakan mikroskopi optik. Pengukuran kekerasan juga dilakukan pada sampel yang sama. XRD digunakan untuk mengetahui komposisi kimia dari spesimen. Keausan specimen diuji dengan menggunakan alat uji tribologi di bawah kondisi kering. Struktur mikro, kekerasan, komposisi kimia dan sifat keausan substrat AISI dianalisa sebelum dan sesudah diberi perlakuan. Hasil uji XRD dan mikro tidak menemukan lapisan karbida niobium-vanadium pada substrat AISI D2. Dalam spesimen yang tidak diberi perlakuan ditemukan kromium karbida (Cr7C3), sehingga tidak ada pasokan karbon yang cukup untuk membentuk niobium-vanadium karbida ketika proses teknik thermo reactive diffusion berlangsung. Selain itu, kromium karbida (Cr7C3) memiliki energi bebas pembentukan terendah dibandingkan dengan NbC dan VC. Sehingga karbida yang terbentuk hanya pada substrat dan tidak membentuk lapisan. Spesimen yang tidak diberi perlakuan memiliki nilai kekerasan 277,8 HV. Setelah diberi perlakuan TRD, jumlah kekerasan meningkat. Untuk variasi suhu pemanasan 950°C, 1000°C, dan 1050°C masing-masing memiliki angka kekerasan 798.21HV, 787.3HV, 774.2HV. Nilai kekerasan meningkat karena pengerasan spesimen AISI D2. Nilai ketahanan aus tertinggi dimiliki oleh variasi suhu 950°C dan nilai ketahanan aus terendah dimiliki oleh spesimen yang tidak diberi perlakuan.

Item Type: Thesis (Undergraduate)
Additional Information: RSM 620.112 Kha f-1 2019
Uncontrolled Keywords: thermo-reactive diffusion, niobium-vanadium carbide, AISI D2, hardness, wear.
Subjects: T Technology > TA Engineering (General). Civil engineering (General) > TA169.5 Failure analysis
T Technology > TJ Mechanical engineering and machinery
T Technology > TJ Mechanical engineering and machinery > TJ1230 Cutting and sawing machinery
Divisions: Faculty of Industrial Technology > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User: Izdada Rotaal Khamda
Date Deposited: 15 Jul 2021 04:23
Last Modified: 15 Jul 2021 04:23
URI: https://repository.its.ac.id/id/eprint/60966

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