The present work addresses the surface hardening and heat treatment response of Ti-6Al-4V grades G5 and G23 on thermochemical surface treatment in different temperature regimes as well as in different gaseous and plasma-based media. Grades G5 and G23 were subjected to gaseous surface hardening using various gas compositions and temperature regimes. Two different series of gaseous surface treatments were carried out:

1)

Carbo-oxidizing of G23 in mill-annealed condition was performed in CO gas at (high) temperatures ranging from 777 to 1027 °C. Treatment at 1027 °C resulted in the deepest case with the formation of a thin surface layer of titanium sub-oxides supported by a thick TiC_xO_1-x layer as the dominant phase. Post-nitriding of the carbo-oxidized specimen raised the hardness of the TiC_xO_1-x phase by the incorporation of nitrogen, yielding values up to ~2900 HV and multi-layered structures.

2)

Carbo-oxidizing of G5 with a bi-modal microstructure in CO/CO₂ gas mixture at (intermediate) temperatures in the range 677–777 °C. Treatment at 777 °C resulted in a surface hardness of ~1900 HV and a ~60 μm-thick diffusion zone.

In addition to gaseous surface hardening, also plasma-assisted methods were applied and compared to their gaseous counterparts. Intermediate- and low-temperature plasma treatments were carried out on G23:

3)

Plasma (carbo-nitro)oxidizing was performed in a CO₂ and N₂ gas mixture at 750 °C and (carbo-)oxidizing in CO₂ gas at 650 °C.

4)

Plasma nitriding was conducted in a N₂/H₂ gas mixture at 750 °C and 850 °C. The widely different types of treatments applied in this work represent the diversity of the gaseous and plasma-based thermochemical methods that can be applied for surface engineering of titanium alloys.

目前的工作解决了 Ti-6Al-4V 牌号 G5 和 G23 在不同温度范围以及不同气体和等离子介质中对热化学表面处理的表面硬化和热处理响应。等级 G5 和 G23 使用各种气体成分和温度范围进行气态表面硬化。进行了两种不同系列的气态表面处理：

1)

G23 在轧机退火条件下的碳氧化是在 CO 气体中在 777 至 1027 °C 的（高温）温度范围内进行的。在 1027 °C 下处理导致最深的情况是形成由厚 TiC _x O _1-x层支撑的钛亚氧化物薄表面层作为主要相。碳氧化试样的后氮化通过掺入氮提高了 TiC _x O _1-x相的硬度，产生高达 ~2900 HV 的值和多层结构。

2)

在 677–777 °C 范围内的（中间）温度下，在 CO/CO ₂气体混合物中对具有双峰微观结构的 G5 进行碳氧化。在 777 °C 下处理导致表面硬度为 ~1900 HV 和 ~60 μm 厚的扩散区。

除了气态表面硬化外，还应用了等离子辅助方法，并与其气态对应方法进行了比较。G23 进行了中低温等离子处理：

3)

等离子体（碳-硝基）氧化在 CO ₂和 N ₂气体混合物中在 750°C 下进行，在 CO ₂气体中在 650°C 下进行（碳-）氧化。

4)

等离子氮化在 N ₂ /H ₂气体混合物中在 750°C 和 850°C 下进行。在这项工作中应用的广泛不同类型的处理代表了可用于钛合金表面工程的气体和等离子体基热化学方法的多样性。