Objectives

The application of selective laser melting (SLM) to dentistry has been rapidly expanding; however, SLM-processed parts possess orientation-dependent properties (i.e., anisotropy) that can affect the long-term reliability of the dental prostheses. This study aimed to evaluate the anisotropic corrosion response of SLM-processed Co–Cr–Mo alloys under various heat treatments.

Methods

Samples fabricated via SLM along the horizontal plane (x-y plane) and vertical plane (x-z plane), with respect to the build direction, were subjected to various heat treatments. The resulting microstructures of the samples were characterized, and their corrosion properties were evaluated using anodic polarization and immersion tests.

Results

All samples showed similar transpassive behavior of the polarization curves. However, the immersion tests showed that the as-built x-z plane samples released significantly more metal ions than those fabricated on the x-y plane because of the larger area of preferentially corroded molten pool boundaries (MPBs) in the x-z plane samples. Our results further demonstrated that the heat treatments eliminated the MPBs, resulting in isotropic corrosion properties. However, excessive heat treatment at high temperatures induces the formation of coarse precipitates, resulting in a less-protective passive film.

Significance

The post-build heat treatments at temperatures that eliminate the MPBs are effective in reducing anisotropic corrosion behavior, and the lowest possible temperature is suitable for reducing the amount of released metal ions. These findings are expected to facilitate the application of SLM in dentistry to allow fast and precise production of prosthetic devices.

中文翻译：

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通过后热处理降低选择性激光熔融Co-Cr-Mo合金腐蚀性能的各向异性响应

目标

选择性激光熔化（SLM）在牙科领域的应用正在迅速扩展。但是，经SLM处理的零件具有与方向有关的特性（即各向异性），这些特性会影响假牙的长期可靠性。这项研究旨在评估在不同热处理条件下SLM处理的Co-Cr-Mo合金的各向异性腐蚀响应。

方法

相对于构建方向，沿着水平面（xy平面）和垂直平面（xz平面）通过SLM制作的样品要进行各种热处理。表征样品的微观结构，并使用阳极极化和浸没测试评估其腐蚀性能。

结果

所有样品均显示出相似的极化曲线的超被动行为。但是，浸没测试表明，由于xz平面样品中优先腐蚀的熔池边界（MPB）的面积较大，因此建成的xz平面样品释放的金属离子明显多于xy平面上制造的金属离子。我们的结果进一步表明，热处理消除了MPB，从而导致各向同性的腐蚀性能。但是，高温下的过度热处理会导致形成粗大的沉淀，从而导致保护性较低的钝化膜。

意义

在消除MPB的温度下进行的建后热处理可有效减少各向异性腐蚀行为，并且尽可能低的温度适用于减少释放的金属离子量。预期这些发现将促进SLM在牙科中的应用，从而可以快速，精确地生产修复装置。