Sains Malaysiana 44(8)(2015): 1175–1181

Effects of Vanadium Carbide on Sintered WC-10%Co Produced by Micro-powder Injection Molding

(Kesan Vanadium Karbida ke atas WC-10%Co Bersinter dihasilkan melalui Pengacuan Suntikan Serbuk Mikro)

WONG YEE NING, NORHAMIDI MUHAMAD, ABU BAKAR SULONG*, ABDOLALI FAYYAZ & MUHAMMAD RAFI RAZA

Department of Mechanical & Materials Engineering, Faculty of Engineering & Built Environment

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

Received: 17 July 2014/Accepted: 14 April 2015

ABSTRACT

Ultrafine, cemented tungsten carbide (WC) possesses exceptional hardness, wear resistance and high strength in various applications. In this study, WC was produced through micro powder injection molding (μPIM), which is also applicable for metals and ceramics in producing complex parts with high-dimensional accuracy. Different inhibitors, such as VC, Cr₂C₃, NbC, or TaC, were added to improve the mechanical properties of WC and control its grain growth. The effects of a grain growth inhibitor were investigated by adding VC in WC–10%Co–nVC, where n = 0 to 1.2 wt. %. The mechanical properties of the sintered part, such as hardness and flexural strength, were determined. The morphology and elemental distribution of the samples were studied by field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. X-ray diffraction was employed to study the phases of the obtained samples. The results showed that the sample with 0.4 wt. % VC (optimal amount) sintered at 1410°C exhibited the highest theoretical density, hardness and flexural strength of 95.2%, 1973±31 HV and 2586±172 MPa, respectively. The average grain size measured was 519±27 nm. VC acted as a grain growth inhibitor during sintering, thereby improving the mechanical properties.

Keywords: Flexure strength; grain growth inhibitor; microstructure; micro powder injection moulding; XRD

ABSTRAK

Ultra halus, tungsten karbida terikat (WC) memiliki ciri kekerasan yang tinggi, rintangan haus dan kekuatan yang tinggi dalam pelbagai aplikasi. Dalam kajian ini, WC dihasilkan melalui pengacuan suntikan serbuk mikro (μPIM) yang turut digunakan dalam bidang logam dan seramik untuk menghasilkan produk kompleks dengan ketepatan dimensi yang tinggi. Perencat lain seperti VC, Cr₂C₃, NbC atau TaC telah ditambah untuk meningkatkan sifat mekanik WC dan mengawal pertumbuhan butirnya. Kesan perencat pertumbuhan butir telah dikaji dengan menambah VC ke dalam WC-10%Co-nVC dengan n=0 - 1.2 wt. %. Sifat mekanik pada bahagian bersinter seperti kekerasan dan kekuatan lenturan diukur. Taburan morfologi dan unsur sampel dikaji dengan pancaran medan mikroskop imbasan elektron (FESEM) dan spektroskopi tenaga penyebar sinar-x. Pembelauan sinar-X digunakan untuk mengkaji fasa sampel yang diperoleh. Keputusan menunjukkan sampel dengan 0.4 wt. % VC (jumlah optimum) yang disinter pada suhu 1410^oC mencatatkan teori ketumpatan tertinggi, kekerasan dan kekuatan lenturan masing-masing pada 95.2%, 1973±31 HV dan 2586±172  MPa. Purata saiz butir yang dikira ialah 519±27 nm. VC berperanan sebagai perencat pertumbuhan butir semasa proses pensinteran, justeru memperbaiki sifat mekaniknya.

Kata kunci: Kekuatan lenturan; mikrostruktur; pengacuan suntikan serbuk mikro; perencat pertumbuhan butir; XRD

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*Corresponding author; email: abubakar@ukm.edu.my