Abstract We implement the meridian crack test method to measure the surface and subsurface flaw-controlled strength of spherical near-eutectic plasma-sprayed alumina-zirconia-silica particles of average diameter near 30 μm. The particles are tested in two states, namely as-sprayed amorphous, or nanocrystalline as obtained after a supplementary annealing step. The test consists in uniaxial compression testing of individual particles between a pair of elasto-plastic steel platens, the hardness of which is tailored to achieve relative contact radii (defined as the ratio between the radius of the projected particle-platen contact area to the particle radius) above 0.6 at the moment of particle failure. Results show that nanocrystalline particles exhibit characteristic Weibull strength 1490 MPa, which is approximately 30% higher than for amorphous particles while the Weibull modulus is, relative to the test precision, comparable, being equal to 6.0 and 7.8 for nanocrystalline and amorphous particles, respectively. This result is an indication that the flaw size distribution is not significantly affected by the annealing step, the strength increase resulting from an increase in fracture toughness upon nanocrystallisation. This conclusion is consistent with fractographic observations. The principal strength-limiting defects identified for both amorphous and nanocrystalline particles were micropores formed during plasma spraying.

中文翻译：

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等离子喷涂非晶和纳米晶陶瓷微粒子午裂试验强度

摘要 我们采用子午裂纹测试方法来测量平均直径接近 30 μm 的球形近共晶等离子喷涂氧化铝-氧化锆-二氧化硅颗粒的表面和亚表面缺陷控制强度。颗粒在两种状态下进行测试，即喷涂后的非晶态或在补充退火步骤后获得的纳米晶态。该测试包括对一对弹塑性钢压板之间的单个颗粒进行单轴压缩测试，其硬度经过调整以实现相对接触半径（定义为颗粒-压板投影接触面积与颗粒的半径之比）半径）大于 0.6 在粒子失效的时刻。结果表明纳米晶颗粒表现出特征威布尔强度 1490 MPa，这比无定形颗粒高约 30%，而威布尔模量相对于测试精度而言具有可比性，对于纳米晶和无定形颗粒分别等于 6.0 和 7.8。该结果表明缺陷尺寸分布不受退火步骤的显着影响，由于纳米结晶时断裂韧性的增加而导致强度增加。该结论与断层观察一致。非晶和纳米晶颗粒的主要强度限制缺陷是等离子喷涂过程中形成的微孔。该结果表明缺陷尺寸分布不受退火步骤的显着影响，由于纳米结晶时断裂韧性的增加而导致强度增加。这一结论与断层观察一致。非晶和纳米晶颗粒的主要强度限制缺陷是等离子喷涂过程中形成的微孔。该结果表明缺陷尺寸分布不受退火步骤的显着影响，由于纳米结晶时断裂韧性的增加而导致强度增加。这一结论与断层观察一致。非晶和纳米晶颗粒的主要强度限制缺陷是等离子喷涂过程中形成的微孔。