目的 采用热扩散法碳化物覆层处理技术，研究细长孔内壁的成层厚度、覆层形貌，以及对细长孔内壁表面硬度性能的影响;探究在不同孔径和孔长条件下，采用热扩散法碳化物覆层处理技术在孔内表面形成覆层的微观形貌及形成原因。方法 采用目前使用最为广泛的碳化钒覆层配方对试样进行覆层处理，在试样内壁表面得到各组对应的碳化钒覆层;利用X粉末衍射实验(XRPD)分析处理结束后内表面的物相组成，利用光学显微镜观察形成覆层的厚度，利用扫描电子显微镜(SEM)对表面覆层的微观组织进行分析，并采用划痕法测试其结合强度，利用显微硬度计测量其表面硬度。结果 在不同孔径的孔内壁均生成了一层碳化钒覆层。3 mm孔样品的覆层厚度相对最薄(3.06 μm)，6 mm孔样品的覆层厚度相对最厚(5.29 μm);在硬度测试实验中，与未进行覆层处理的原材料相比，覆层后孔内壁的硬度均得到了强化，且6 mm孔样品的强化效果相对最佳，其表面硬度达到了1 767.8HV2/15。结论 经热扩散法碳化物覆层处理技术处理后得到的内表面覆层厚度随着孔径的增加而增加，同时覆层的厚度、表面硬度等均与孔径呈正相关;随着孔长的变化，成层厚度等出现先下降后上升的趋势;所形成的碳化钒覆层均能够有效提高材料的表面硬度。

The work aims to study the effects of TD treatment technology on the forming thickness, morphology and surface hardness of the inner wall of the slender hole, and the micro-morphology and formation reasons of the coating formed on the inner surface of the hole by thermal diffusion carbide coating treatment technology under the conditions of different hole diameters and hole lengths. The most widely used vanadium carbide coating formula was applied to coat the sample, and the corresponding vanadium carbide coatings were obtained on the inner wall surface of the sample. The phase composition of the inner surface after treatment was analyzed by X-ray powder diffraction experiment (XRPD). The thickness of the formed coating was measured with an optical microscope. The microstructure of the surface coating was analyzed with a scanning electron microscope (SEM). The bond strength between the coating and the substrate was measured with a scratch tester. The surface hardness was measured with a microhardness tester. A layer of vanadium carbide coating was successfully found on the inner wall surface of holes with different hole diameters. The thinnest part was 3.06 μm of 3 mm hole sample. The thickest part was 5.29 μm of 6 mm hole sample. In the hardness test experiment, compared with the raw materials without coating treatment, the hardness of the inner wall of the hole after coating was strengthened. The strengthening effect of 6 mm hole was the best. The maximum surface hardness reached 1 767.8HV2/15. The thickness of inner surface coating after TD treatment increases with the increase of hole diameter. At the same time, the thickness and surface hardness of the coating are positively correlated with the hole diameter. With the change of hole length, it will decrease first and then increase. The vanadium carbide coating formed can effectively improve the surface hardness of the material.