抗彎強(qiáng)度的影響
(1. 中南大學(xué) 粉末冶金國家重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410083；
2. 自貢硬質(zhì)合金有限責(zé)任公司，自貢 643011)
摘 要: 采用預(yù)燒結(jié)-后續(xù)滲碳的方法制備鈷相呈梯度分布的硬質(zhì)合金，通過對(duì)試樣顯微組織的觀察和抗彎強(qiáng)度的測(cè)試，研究滲碳時(shí)間對(duì)梯度硬質(zhì)合金顯微組織和抗彎強(qiáng)度的影響。結(jié)果表明：試樣富鈷層鈷相含量隨滲碳時(shí)間的延長(zhǎng)而增加，試樣的抗彎強(qiáng)度隨滲碳時(shí)間出現(xiàn)了峰值現(xiàn)象，即當(dāng)滲碳時(shí)間少于140 min時(shí)，試樣的抗彎強(qiáng)度隨滲碳時(shí)間的增加而增加，在滲碳處理140 min時(shí)出現(xiàn)最大值，當(dāng)滲碳160 min后，試樣的抗彎強(qiáng)度開始下降。分析認(rèn)為，富鈷層中金屬鈷的良好塑性變形能力能有效地吸收來自外部裂紋擴(kuò)展的能量，提高合金的抗彎強(qiáng)度，同時(shí)當(dāng)滲碳時(shí)間過長(zhǎng)時(shí)(超過140 min)，WC與η相晶粒出現(xiàn)了聚集長(zhǎng)大，造成鈷相分布不均勻，并局部形成Co池，導(dǎo)致試樣抗彎強(qiáng)度的下降。對(duì)于直徑為10 mm的礦用梯度球齒，其合理的滲碳時(shí)間應(yīng)控制在120~140 min。
關(guān)鍵字: 硬質(zhì)合金；梯度結(jié)構(gòu)；滲碳；顯微組織；抗彎強(qiáng)度
and transverse rupture strength of
graded cemented carbides
（1. State Key Laboratory for Powder Metallurgy, Central South University,
Changsha 410083,China;
2. Zigong Cemented Carbide Co. Ltd., Zigong 643011, China）
Abstract:Effects of carburizing time on microstructure and transverse rupture strength of cemented carbide with gradient cobalt structure fabricated by pre-sintering-carburizing process were studied by optical microscopy and transverse rupture strength test. The results show that the cobalt content in the Co-rich layer increases with prolonging carburizing time, the transverse rupture strength of samples increases when carburizing time is less than 140 min and the maximum appears at 140 min. The transverse rupture strength increases efficiently because of the tough Co-rich layer in samples. The distinct decreasing of the transverse rupture strength carburized for more than 140 min is ascribed to the grain growth of WC and η phase. The reasonable carburizing time should be controlled in 120−140 min for the d 10 mm samples.
Key words: cemented carbide; gradient structure; carburizing; microstructure; transverse rupture strength
