熱均壓處理及燒結參數對WC-12 wt%Co的機械性質之影響

Effect of Mechanical Properties on WC-12wt%Co via HIP Treatment and Sintering Parameters

李仲偉(Chung-Wei Lee)

指導教授 ： 唐自標 ； 張世賢

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2010年)

https://doi.org/10.6841/NTUT.2010.00282

摘要

碳化鎢(WC-Co)複合材料因具優越的機械性質、切削性能及耐磨耗能力，在工業界常被應用於需要在嚴苛條件下操作的機械工具、鑽鑿工具和耐磨耗零件上。而此類超硬合金因熔點高，多採用粉末冶金方式製造。熱均壓技術為一種同時結合了高溫與高壓的熱處理，其加壓媒介為惰性氣體，且對於工件所施的壓力在各方向均相等。現今熱均壓技術已被廣泛應用於粉末冶金工業上，以去除工件內部的封閉孔隙與缺陷，來改善材料的機械及物理性質。
由實驗結果中發現，WC-12wt%Co在燒結過程中發生良好之液相燒結時，試片可幾乎不具孔隙，並表現出優良之機械性質。碳化鎢材料G5經燒結溫度1400℃與F12經燒結溫度1350℃與1400℃燒結1小時之後，其相對密度可達98-99%，HRA硬度值分別達到88與92以上，而抗折強度則分別為2398 MPa與2200 MPa。
當燒結溫度過高時，η相(Co3W3C phase)的大量析出來自於主成分為Co之液相聚集於試片特定區域，再與WC顆粒反應而生成，此現象亦發生於本實驗使用熱均壓處理參數之試片，使其抗折強度降低。因試片內之Co3W3C相大量生成時，將使WC顆粒間之黏結相平均厚度減少，且因Co3W3C相本身為硬而脆，故使得試片抗折強度下降。

關鍵字

碳化鎢 ； 粉末冶金 ； 熱均壓

並列摘要

Tungsten carbide (WC-Co) composites are widely used in industry such as machining tools, mining tools, and wear-resistant parts operated in critical condition which with superior mechanical properties, cutting performance and wear-resistant abilities. Because of the high melting point, this kind of hard metal is mostly manufactured by powder metallurgy method. Hot isostatic pressing (HIP) technique is a heat treatment method which combines high temperature and high pressure. Furthermore, the pressure medium is used inert gas, and it exerted on the work-piece in all direction are equal. Recently HIP technique has been wildly used in powder metallurgy industry to eliminate the isolated pores and defects inside the work-piece. Therefore, the mechanical and physical properties of materials can be improved.
The experimental result indicated that the specimen of WC-12wt% Co contained few pores and showed the excellent mechanical properties, because the well liquid phase sintering was occurred during sintering progress. The specimen of G5 sintered at 1400℃ for one hour achieved 98% of relative density, and hardness was HRA 88, TRS increased to 2398 MPa, respectively. Moreover, all the specimens of F12 sintered at 1350℃ and 1400℃ for one hour achieved 99% of relative density, and hardness was HRA 92, TRS also enhanced to 2200 MPa.
In this study, a large amount of η phase (Co3W3C) precipitations at high sintering temperature. The precipitations were generated by liquid phase (mainly contain was cobalt) particularly gathered in some special region of specimen, and then reacted with the WC particles. The phenomenon also could be obviously found in the specimens by HIP treated parameters, therefore the TRS of specimens were decreased. When a large amount of Co3W3C phase has been generated, the thickness of average binder’s phase between WC particles was decrease. Furthermore, Co3W3C was a hard and brittle phase, it will result in the lower TRS of specimens.

並列關鍵字

Tungsten Carbide ； Vacuum Sintering ； Hot Isostatic Pressing

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