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Effect of surface heat transfer coefficient gradient on thermal shock failure of ceramic materials under rapid cooling condition
Ceramics International ( IF 5.2 ) Pub Date : 2018-06-01 , DOI: 10.1016/j.ceramint.2018.02.100
Limin Chen , Anzhe Wang , Xiangbo Suo , Ping Hu , Xinghong Zhang , Zhengjun Zhang

Abstract A rapid thermal processor (RTP) device as well as quenching technique is employed to systematically investigate the effect of surface heat transfer coefficient (h) gradient on thermal shock failure of a hot-pressed ZrB2-based ceramic. Two typical kinds of quenchant with different surface h gradients during quenching tests, water and boiling water, are used for this study. When water as the cooling medium, two different cooling modes of indirect contact cooling by RTP device and direct contact cooling by quenching are also studied. The experimental results and related numerical simulations illustrate that surface h gradient plays an important role in thermal shock failure. This study confirms the previous presumption that the combination of body temperature gradient and surface h gradient leads to thermal stress damage and thermal shock failure. Under water quenching condition, water phase changes form bubbles randomly and produce great surface h gradient. Accordingly, critical body temperature gradient (V(max)c) is small (~ 270 °C s−1). Under aqueous polymer quenching condition, the introduction of polymer chains into water lowers the random formation of steam bubble and mediates the surface h gradient. The corresponding V(max)c hence become larger (~ 500 °C s−1). Under boiling water quenching condition, there is no surface h gradient and V(max)c is even larger (> 600 °C s−1). This study provides useful complementary information for understanding the thermal shock behavior and gives suggests for predicting materials performance in actual service.

中文翻译:

快速冷却条件下表面传热系数梯度对陶瓷材料热冲击失效的影响

摘要 采用快速热处理器 (RTP) 装置和淬火技术,系统地研究了表面传热系数 (h) 梯度对热压 ZrB2 基陶瓷热冲击失效的影响。本研究使用两种在淬火试验中具有不同表面 h 梯度的典型淬火剂,即水和沸水。还研究了以水为冷却介质的RTP装置间接接触冷却和淬火直接接触冷却两种不同的冷却方式。实验结果和相关数值模拟表明,表面 h 梯度在热冲击失效中起着重要作用。该研究证实了先前的假设,即体温梯度和表面 h 梯度的组合导致热应力损伤和热冲击失效。在水淬条件下,水相变化随机形成气泡,产生很大的表面h梯度。因此,临界体温梯度 (V(max)c) 很小 (~ 270 °C s-1)。在水性聚合物淬火条件下,将聚合物链引入水中降低了蒸汽气泡的随机形成并调节了表面 h 梯度。相应的 V(max)c 因此变得更大(~500 °C s-1)。在沸水淬火条件下,没有表面 h 梯度,V(max)c 甚至更大(> 600 °C s-1)。
更新日期:2018-06-01
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