Cemented carbide materials develop very large micro-stresses due to the coefficient of thermal expansion (CTE) mismatch between the metallic carbide phase and the binder phase. While micro-stresses developed in WC-Co cemented carbides have been investigated, there is very little to no information on the micro-stresses developed in NbC-Ni materials.

In this study the thermal stresses developed in NbC-Ni materials as a function of the carbide grain size (from 2.5 μm to 12.8 μm) and the binder content (from 8 vol% to 12 vol%) were characterized by neutron diffraction. It was found that the residual stresses decreased with the increase of the binder content and the increase of the carbides grain size. For both binder and carbide phases, stresses were higher for smaller NbC particles, reaching 4 GPa in Ni at the lowest binder content. In general, stresses were higher than the ones measured in WC-Co or WC-Ni composites. This unexpected finding was attributed to the very different shapes presented by the carbide particles; NbC particles are almost spherical, and WC particles are triangular plates with truncated corners. These different shapes create different strain/stress distributions on the microscopic level around the carbide particles.

由于金属碳化物相和粘合剂相之间的热膨胀系数 (CTE) 不匹配，硬质合金材料会产生非常大的微应力。虽然已经研究了 WC-Co 硬质合金中产生的微应力，但几乎没有关于 NbC-Ni 材料中产生的微应力的信息。

在这项研究中，NbC-Ni 材料中产生的热应力随碳化物晶粒尺寸（从 2.5 μm 到 12.8 μm）和粘合剂含量（从 8 vol% 到 12 vol%）的变化通过中子衍射进行了表征。发现残余应力随着粘结剂含量的增加和碳化物晶粒尺寸的增加而减小。对于粘结剂和碳化物相，较小的 NbC 颗粒的应力较高，在最低粘结剂含量下达到 4 GPa。一般来说，应力高于在 WC-Co 或 WC-Ni 复合材料中测得的应力。这一出乎意料的发现归因于碳化物颗粒呈现出非常不同的形状。NbC 颗粒几乎是球形的，WC 颗粒是带有截角的三角形板。