梯形裂紋的形成機(jī)理
(合肥工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院， 合肥 230009)
摘 要: 在自約束型熱疲勞試驗(yàn)機(jī)上對碳化鎢含量不同的鋼結(jié)硬質(zhì)合金進(jìn)行了熱疲勞試驗(yàn)， 用金相顯微鏡和掃描電鏡對熱疲勞裂紋擴(kuò)展行為進(jìn)行了研究。結(jié)果表明： 在熱應(yīng)力作用下， 不僅在合金的表面， 在合金的內(nèi)部都形成了“梯形”裂紋。 這種形態(tài)的裂紋是由試樣缺口處的熱疲勞裂紋擴(kuò)展而引起的， 合金中的鋼基體相阻礙裂紋擴(kuò)展， 而WC硬質(zhì)相誘導(dǎo)裂紋擴(kuò)展， 這兩種因素的綜合作用促使熱疲勞裂紋成“梯形”擴(kuò)展。 分析認(rèn)為： 使WC粒子在鋼基體中均勻分布， 提高鋼基體的熱疲勞抗力， 從而來阻止梯形裂紋的形成，是提高碳化鎢鋼結(jié)硬質(zhì)合金抗熱疲勞性能的有效途徑。
關(guān)鍵字: 碳化鎢；鋼結(jié)硬質(zhì)合金；熱疲勞；裂紋擴(kuò)展
（Institute of Materials Science and Engineering,
Hefei University of Technology, Hefei 230009, China）
Abstract:Thermal fatigue test of two kinds of WC steel bonded carbides with different WC contents was examined on self-strained thermal fatigue testing machines, and thermal fatigue crack propagation process was investigated by optical microscopy and SEM. The results show that a kind of trapezoid crack forms not only on the surface but also in the alloy, and the forming process of this kind of crack is the propagation process of the thermal fatigue crack that forms at the sample notch. Steel matrix prevents the crack from propagating, and WC hard phase induces the crack to propagate. The comprehensive effects of these two factors make thermal fatigue crack form trapezoid crack shape .It is pointed out by analyzing that making WC particles distribute uniformly in the steel matrix and increasing thermal fatigue resistance of the matrix to prevent trapezoid crack from forming are effective methods to increase the thermal fatigue resistance of WC steel bonded carbides.
Key words: WC(tungsten carbide)； steel bonded carbide； thermal fatigue； crack propagation
