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分类。高温摩擦学

 

High temperature hardness testing for materials exposed to extreme thermal conditions in aerospace and defense applications

High Temperature Brinell Hardness Testing

Application Note | High Temperature Mechanical Testing

High Temperature Hardness Testing of Steel Using Brinell Indentation

Mapping Steel Hardness Loss from Room Temperature to 925°C with NANOVEA T2000 Tribometer

Material performance testing under extreme temperature conditions for aerospace and defense applications

Research & Experimental Testing

Frank Liu

Visual Design & Editorial

安德鲁-肖尔

简介

High temperature hardness testing provides insight into how the mechanical behavior of metals changes as temperature increases. Materials that exhibit high hardness at room temperature can soften significantly when exposed to elevated temperatures, making temperature-dependent hardness an important consideration when selecting materials for applications such as jet engines, high-temperature processing equipment, and other thermally demanding environments.

In this study, a steel sample was evaluated using Brinell indentation with the NANOVEA T2000 Tribometer. Hardness measurements were performed at 25, 200, 400, 600, 800, and 925°C to map the change in steel hardness with temperature. The results show a gradual reduction in hardness through approximately 600°C, followed by a much sharper decline at higher temperatures, resulting in an 84% decrease in hardness between room temperature and 925°C.

Why High Temperature Hardness Testing Matters

Hardness is a mechanical property that describes a material’s resistance to localized deformation. Higher hardness generally corresponds to greater resistance to indentation and permanent surface deformation.

Temperature can significantly alter this behavior. A material that remains hard at room temperature may soften as temperature increases, changing its mechanical response under elevated-temperature conditions. For materials intended for high-temperature applications, understanding these changes is important when evaluating their mechanical limits.

High temperature hardness testing makes it possible to measure these changes directly as temperature increases rather than relying only on room-temperature properties. In this study, the steel sample provides a clear example of how hardness can remain relatively stable over part of the temperature range before declining rapidly at higher temperatures.

测量目标

The objective of this study was to evaluate how the Brinell hardness of steel changes as temperature increases from room temperature to 925°C.

Using a 10 mm tungsten carbide (WC) ball, a load of 1000 N (~100 kgf) was applied to the steel sample at 25, 200, 400, 600, 800, and 925°C. The resulting indentations were measured using NANOVEA’s 3D Line Sensor to determine their diameter for Brinell hardness calculation.

NANOVEA T2000 高负荷

气动摩擦磨损试验机

测试程序

High temperature Brinell hardness testing was performed with the steel sample mounted inside the NANOVEA T2000 heated chamber. The sample was tested at six temperatures from 25°C to 925°C using a 10 mm tungsten carbide (WC) ball with an applied test force of 1000 N (~100 kgf).

The test parameters used throughout the study are summarized below.

Steel sample mounted inside the NANOVEA T2000 high temperature chamber for Brinell hardness testing

Steel sample mounted in the NANOVEA T2000 high temperature chamber for Brinell hardness testing from 25°C to 925°C.

测试参数

Test Parameter High Temperature Brinell Hardness Setup
温度 25, 200, 400, 600, 800, 925°C
Test force 1000 N (~100 kgf)
Force-diameter ratio 1
Ball material Tungsten carbide (WC)
Ball diameter 10毫米
Steel samples used for high temperature Brinell hardness testing from 25°C to 925°C

Steel samples used in the high temperature Brinell hardness study from room temperature to 925°C.

结果和讨论

Brinell hardness was calculated from the applied force, ball diameter, and measured indentation diameter using the equation below:

Brinell hardness equation using applied force, ball diameter, and measured indentation diameter

Where F (kgf) is the applied force expressed in kilogram-force, D is the ball diameter, and d is the measured indentation diameter. Two diameter measurements were taken for each indent and averaged to determine the value of d used in the hardness calculation.

Load versus time curve showing the 1000 N indentation load used during high temperature Brinell hardness testing of steel

Load vs. time profile for the 1000 N Brinell indentations performed during high temperature hardness testing.

The loading curve shows the applied load profile used during indentation. A consistent 1000 N (~100 kgf) test force was used throughout the temperature series so that the resulting indentation dimensions and calculated hardness values could be compared across each test condition.

Brinell indentation on steel measured at 800°C with diameters of 1.807 mm and 1.830 mm
距离 Unit A B
HDist 毫米 1.807 1.830

Brinell indentation measured at 800°C. Two diameter measurements of 1.807 mm and 1.830 mm were averaged to determine the indentation diameter used for hardness calculation.

At 800°C, the measured indentation diameters were 1.807 mm and 1.830 mm, producing an average diameter of approximately 1.819 mm. The indentation diameter increased substantially at the higher test temperatures as the steel became softer under the same applied load.

The measured indentation diameters were then used to calculate Brinell hardness at each temperature. The results show a relatively gradual decrease from 96.12 HBW at 25°C to 79.69 HBW at 600°C, followed by a much sharper decrease to 38.18 HBW at 800°C and 15.40 HBW at 925°C.

Brinell Hardness Results

High Temperature Brinell Hardness Results
Temperature (°C) Diameter 1 (mm) Diameter 2 (mm) Average Diameter (mm) HBW (10/100)
25 1.153 1.145 1.149 96.12
200 1.150 1.201 1.176 91.82
400 1.165 1.261 1.213 86.21
600 1.265 1.258 1.262 79.69
800 1.807 1.830 1.819 38.18
925 2.858 2.833 2.846 15.40
Graph showing Brinell hardness of steel decreasing from 96.12 HBW at 25°C to 15.40 HBW at 925°C

The temperature-dependent trend is clear. Steel hardness decreased moderately between room temperature and 600°C, then declined rapidly at higher temperatures. Between 25°C and 925°C, the measured Brinell hardness decreased from 96.12 to 15.40 HBW, representing an overall hardness loss of approximately 84%.

These results demonstrate why hardness measured at room temperature alone may not fully represent material behavior in high-temperature applications. For this steel sample, the most substantial loss in hardness occurred above approximately 600°C.

总结

High temperature hardness testing revealed a strong temperature-dependent change in the Brinell hardness of the steel sample. Hardness decreased gradually as temperature increased from 25°C to 600°C, then declined much more sharply at higher temperatures. By 925°C, the measured hardness had fallen from 96.12 HBW to 15.40 HBW, representing an overall decrease of approximately 84%.

The study demonstrates the ability of the NANOVEA T2000 Tribometer to perform Brinell hardness measurements under elevated-temperature conditions. Using a 1000 N (~100 kgf) test force, the steel sample was evaluated from 25°C to 925°C, allowing its change in hardness to be measured directly across the tested temperature range.

The results also highlight the importance of selecting an appropriate force-diameter ratio across a wide temperature range. Because of the large difference in hardness between room temperature and high temperature, the study recommends a force-diameter ratio of 5 or 10 at lower temperatures, while a ratio of 1 is suitable above 900°C.

Frequently Asked Questions About High Temperature Hardness Testing

What is high temperature hardness testing used for?

High temperature hardness testing evaluates how a material’s resistance to indentation changes as temperature increases. It is useful for materials intended for thermally demanding applications where room-temperature hardness may not represent mechanical behavior at operating temperature.

Can Brinell hardness be measured at elevated temperatures?

Yes. Elevated-temperature Brinell hardness testing applies a controlled force using a ball of known diameter while the specimen is heated to the required test temperature. In this study, steel was tested from 25°C to 925°C using a 10 mm tungsten carbide ball and a 1000 N test force.

Why measure hardness while the material is hot?

Testing at temperature measures hardness under the thermal condition of interest rather than only after the specimen returns to room temperature. This makes it possible to directly characterize temperature-dependent softening and identify changes that may not be represented by room-temperature hardness values.

What equipment is used for high temperature hardness testing?

High temperature hardness testing requires controlled specimen heating, precise mechanical loading and measurement of the resulting indentation. The NANOVEA T2000 can integrate high-temperature environmental control with mechanical testing for evaluating material behavior under elevated-temperature conditions.

Can high temperature hardness testing be used for aerospace materials?

Yes. Elevated-temperature hardness measurements are relevant when evaluating materials intended for thermally demanding aerospace environments, including jet-engine and other high-temperature components. Testing helps characterize how hardness changes as exposure temperature increases.

Can NANOVEA perform high temperature hardness testing as a laboratory service?

NANOVEA provides materials testing services using its mechanical testing and tribology platforms. Application requirements, temperature range, load, specimen geometry and measurement method can be reviewed with a NANOVEA applications engineer to determine an appropriate high-temperature testing approach.

摩擦试验机测高温下划痕硬度

高温划痕硬度

使用摩擦仪

编写者

杜安杰,博士

简介

硬度衡量的是材料对永久或塑性变形的抵抗力。划痕硬度测试最初是由德国矿物学家弗里德里希-莫尔斯在1820年开发的,它确定了材料对尖锐物体的摩擦造成的划痕和磨损的硬度。1.莫氏标度是一个比较指数,而不是一个线性标度,因此,ASTM标准G171-03所述,开发了一个更准确和定性的划痕硬度测量方法。2.它测量金刚石测针产生的划痕的平均宽度并计算出划痕硬度数(HSP)。

高温下测量划痕硬度的重要性

材料是根据服务要求来选择的。对于涉及重大温度变化和热梯度的应用,测试材料在高温下的机械性能以充分了解其机械极限是至关重要的。材料,特别是聚合物,通常在高温下会软化。很多机械故障是由蠕变变形和热疲劳引起的,只有在高温下才会发生。因此,需要一种可靠的技术来测量高温下的硬度,以确保为高温应用正确选择材料。

测量目标

在本研究中,NANOVEA T50 摩擦试验机在室温至 300°C 的不同温度下测量特氟龙样品的划痕硬度。执行高温划痕硬度测量的能力使得 NANOVEA 摩擦仪 用于高温应用材料的摩擦学和机械评估的多功能系统。

NANOVEA

T50

测试条件

NANOVEA T50摩擦试验机可用于室温(RT)到300℃的温度范围内对特氟隆样品进行划痕硬度测试。特富龙的熔点为326.8°C。使用顶角为120°、尖端半径为200 µm的锥形金刚石测针。特氟隆样品被固定在旋转式样品台上,与平台中心的距离为10毫米。样品被烤箱加热,在RT、50°C、100°C、150°C、200°C、250°C和300°C的温度下进行测试。

测试参数

高温划痕硬度的测量

常态力 2 N
滑动速度 1毫米/秒
划痕长度 每个温度8毫米
气体环境 空气
温度 RT, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C。

结果与讨论

为了比较不同温度下的划痕硬度,图1显示了特氟龙样品在不同温度下的划痕轮廓。当测针以2N的恒定载荷行进时,在划痕边缘形成材料堆积,并刺入特氟隆样品,将划痕中的材料推向一侧并使之变形。

如图2所示,在光学显微镜下检查划痕。显微镜测量的划痕宽度和计算出的划痕硬度值(HSP)在图3中进行了总结和比较。 显微镜测量的划痕宽度与使用NANOVEA轮廓仪测量的划痕宽度一致,特氟隆样品在较高温度下表现出更宽的划痕宽度。当温度从RT上升到300℃时,它的划痕宽度从281微米增加到539微米,HSP从65MPa下降到18MPa。

使用NANOVEA T50摩擦磨损仪可以高精度、高重复性地测量高温下的划痕硬度。它提供了一个不同于其他硬度测量的解决方案,并使NANOVEA摩擦仪成为一个更完整的系统,用于全面的高温三坐标机械评估。

图1: 在不同温度下进行划痕硬度测试后的划痕轮廓。

图2: 在不同温度下测量后,显微镜下的划痕痕迹。

图3: 刮痕宽度和刮痕硬度与温度的变化。

结论

在这项研究中,我们展示了NANOVEA摩擦仪如何在高温下测量符合ASTM G171-03标准的划痕硬度。恒定载荷下的划痕硬度测试为使用摩擦仪比较材料的硬度提供了另一种简单的解决方案。在高温下进行划痕硬度测量的能力使NANOVEA摩擦仪成为评估材料高温三相力学性能的理想工具。

NANOVEA摩擦仪还提供精确和可重复的磨损和摩擦测试,使用符合ISO和ASTM标准的旋转和线性模式,在一个预集成的系统中可选择高温磨损、润滑和三相腐蚀模块。可选的3D非接触式轮廓仪,除了用于其他表面测量(如粗糙度)外,还可以对磨损轨迹进行高分辨率的3D成像。

1 Wredenberg, Fredrik; PL Larsson (2009)."金属和聚合物的划痕测试。实验和数值"。磨损266(1-2)。76
2 ASTM G171-03 (2009), "使用金刚石测针测试材料的划痕硬度的标准测试方法"

高温下的原位磨损测量

原位磨损测量 在高温下

使用摩擦仪

就地磨损测量 航空摩擦磨损仪

编写者

李端杰,博士

简介

线性可变差动变压器(LVDT)是一种用于测量线性位移的坚固电气变压器。它已被广泛用于各种工业应用,包括电力涡轮机、液压系统、自动化、飞机、卫星、核反应堆和许多其他应用。

在本研究中,我们展示了 NANOVEA 的 LVDT 和高温模块附加组件 摩擦仪 允许在高温磨损过程中测量测试样品磨损轨迹深度的变化。这使得用户能够将磨损过程的不同阶段与 COF 的演变联系起来,这对于提高对高温应用材料的磨损机制和摩擦学特性的基本了解至关重要。

测量目标

在这项研究中,我们想展示NANOVEA T50摩擦仪在高温下现场监测材料磨损过程的能力。

不同温度下硅酸铝陶瓷的磨损过程是以控制和监测的方式模拟出来的。

NANOVEA

T50

测试程序

摩擦学行为,如摩擦系数,COF,以及硅酸铝陶瓷板的耐磨性是由NANOVEA摩擦仪评估的。硅酸铝陶瓷板被加热炉从室温RT加热到高温(400℃和800℃),然后在这些温度下进行磨损测试。 

为了比较,当样品从800°C冷却到400°C,然后再冷却到室温时,进行了磨损测试。一个AI2O3球头(6毫米直径,100级)被用于测试样品。在现场对COF、磨损深度和温度进行了监测。

测试参数

的引脚在磁盘上的测量

摩擦仪LVDT样品

磨损率K是用公式K=V/(Fxs)=A/(Fxn)来评估的,其中V是磨损体积,F是法向载荷,s是滑动距离,A是磨损轨道的截面积,n是旋转次数。用NANOVEA光学剖面仪评估了表面粗糙度和磨损轨迹轮廓,并用光学显微镜检查了磨损轨迹的形态。

结果与讨论

图1和图2分别显示了现场记录的COF和磨痕深度。在图1中,"-I "表示当温度从RT增加到高温时进行的试验。"D "代表温度从800°C的较高温度下降。

如图1所示,在不同温度下测试的样品在整个测量过程中表现出可比的COF约为0.6。如此高的COF导致了加速的磨损过程,产生了大量的碎屑。如图2所示,在磨损测试期间,通过LVDT监测磨损轨迹深度。在样品加热前和样品冷却后的室温下进行的测试表明,硅酸铝陶瓷板在RT时表现出渐进的磨损过程,在整个磨损测试过程中,磨损轨迹深度逐渐增加,分别为~170和~150μm。 

相比之下,高温(400°C和800°C)下的磨损试验表现出不同的磨损行为--磨损过程开始时,磨损轨迹深度迅速增加,随着试验的继续进行,它的速度减慢。在400°C-I、800°C和400°C-D温度下进行的试验的磨损轨迹深度分别为~140、~350和~210μm。

在不同的温度下进行的针座测试中的COF

图1. 在不同温度下进行的针盘测试中的摩擦系数

不同温度下硅酸铝陶瓷板的磨损轨迹深度

图2. 不同温度下硅酸铝陶瓷板的磨损痕迹深度的演变

不同温度下硅酸铝陶瓷板的平均磨损率和磨损轨迹深度是用 NANOVEA 光学剖析器的概述如下 图3.磨损轨迹的深度与使用LVDT记录的深度一致。硅酸铝陶瓷板在800°C时显示出大幅增加的磨损率,约为0.5 mm3/Nm,而在400°C以下的温度下,磨损率低于0.2 mm3/N。硅酸铝陶瓷板在短暂的加热过程后并没有表现出明显增强的机械/三态性能,在热处理之前和之后拥有相当的磨损率。

硅酸铝陶瓷,也被称为熔岩和奇石,在加热处理之前是柔软的,可以加工。在高达1093°C的高温下进行长时间的烧制,可以大幅提高其硬度和强度,之后需要进行钻石加工。这样一个独特的特性使硅酸铝陶瓷成为雕塑的理想材料。

在这项研究中,我们表明,在短时间内以低于烧制所需的温度(800°C对1093°C)进行热处理并不能改善硅酸铝陶瓷的机械和摩擦学特性,这使得适当的烧制成为这种材料在实际应用中使用前的必要过程。

 
不同温度下样品的磨损率和磨损痕迹深度 1

图3. 不同温度下样品的磨损率和磨损轨迹深度

结论

基于本研究的综合摩擦学分析,我们表明,硅酸铝陶瓷板在从室温到800℃的不同温度下表现出相当的摩擦系数。然而,在800°C时,它显示出大幅增加的磨损率,约为0.5 mm3/Nm,显示出对这种陶瓷进行适当热处理的重要性。

NANOVEA摩擦仪能够评估材料在高达1000℃高温下应用的摩擦学特性。原位COF和磨损轨迹深度测量的功能使用户能够将磨损过程的不同阶段与COF的演变联系起来,这对于提高对高温下使用的材料的磨损机制和摩擦学特性的基本认识至关重要。

NANOVEA摩擦仪使用符合ISO和ASTM标准的旋转和线性模式提供精确和可重复的磨损和摩擦测试,并在一个预集成系统中提供可选的高温磨损、润滑和三相腐蚀模块。NANOVEA无与伦比的产品系列是确定薄或厚、软或硬的涂层、薄膜和基材的全部摩擦学特性的理想解决方案。

可选的3D非接触式轮廓仪,除了用于其他表面测量(如粗糙度)外,还可用于磨损轨迹的高分辨率3D成像。

原地磨损测量

旋转和线性往复磨损(使用Nanovea摩擦计的综合研究)

磨损是由于相对表面的机械作用而导致表面上的材料去除和变形的过程。它受到多种因素的影响,包括单向滑动、滚动、速度、温度等。磨损、摩擦学的研究跨越许多学科,从物理和化学到机械工程和材料科学。磨损的复杂性质需要对特定的磨损机制或过程进行单独的研究,例如粘着磨损、磨料磨损、表面疲劳、微动磨损和冲蚀磨损。然而,“工业磨损”通常涉及协同发生的多种磨损机制。

线性往复和旋转(销盘上)磨损测试是两种广泛使用的符合 ASTM 标准的装置,用于测量材料的滑动磨损行为。由于任何磨损测试方法的磨损率值通常用于预测材料组合的相对排名,因此确认使用不同测试设置测量的磨损率的可重复性极其重要。这使用户能够仔细考虑文献中报告的磨损率值,这对于理解材料的摩擦学特性至关重要。

阅读更多!

用摩擦学评估刹车片


评估防滑垫性能的重要性

刹车片是复合材料,是一种由多种成分组成的材料,必须能够满足大量的安全要求。理想的刹车片具有高摩擦系数(COF),低磨损率,最小的噪音,并在不同的环境下保持可靠。为了确保刹车片的质量能够满足其要求,摩擦学测试可以用来确定关键规格。


刹车片的可靠性被放在非常重要的位置;乘客的安全永远不应该被忽视。因此,复制操作条件并确定可能的故障点是关键。
与纳诺维亚 摩擦仪,在销、球或平面与不断移动的反向材料之间施加恒定负载。两种材料之间的摩擦力通过刚性称重传感器收集,从而可以收集不同负载和速度下的材料特性,并在高温、腐蚀性或液体环境中进行测试。



测量目标

在这项研究中,刹车片的摩擦系数是在从室温到700℃的持续升温环境下研究的。环境温度被就地提高,直到观察到刹车片的明显失效。一个热电偶被连接到针的背面,以测量滑动界面附近的温度。



测试过程和程序




结果和讨论

这项研究主要集中在刹车片开始失效的温度上。获得的COF并不代表现实生活中的数值;销轴的材料与刹车盘不一样。还应注意的是,收集的温度数据是销轴的温度,而不是滑动界面的温度。

 








在测试开始时(室温),SS440C销和刹车片之间的COF给出了一个稳定的值,大约为0.2。随着温度的升高,COF稳步上升,并在350°C附近达到了0.26的峰值。超过390°C,COF迅速开始下降。在450°C时,COF开始回升到0.2,但不久后开始下降到0.05的数值。


刹车片持续失效的温度被确定为500℃以上的温度。超过这个温度,COF就无法再保持0.2的起始COF。



总结




刹车片在超过500℃的温度下显示出一致的故障。其COF为0.2,慢慢上升到0.26的数值,然后在测试结束时(580℃)下降到0.05。0.05和0.2之间的差异是4倍。这意味着在580°C时的法向力必须比室温下的法向力大4倍,才能达到相同的停车力!这就是为什么在580°C时的法向力是4倍。


虽然不包括在这项研究中,Nanovea摩擦仪也能够进行测试,观察刹车片的另一个重要属性:磨损率。通过利用我们的3D非接触式轮廓仪,可以获得磨损轨迹的体积,以计算出样品的磨损速度。磨损测试可以在不同的测试条件和环境下用Nanovea摩擦仪进行,以最好地模拟操作条件。

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高温摩擦学

使用摩擦仪的高温划痕硬度

材料是根据服务要求来选择的。对于涉及重大温度变化和热梯度的应用,调查材料在高温下的机械性能以充分了解其机械极限是至关重要的。材料,特别是聚合物,通常在高温下会软化。很多机械故障是由蠕变变形和热疲劳引起的,只有在高温下才会发生。因此,需要一种可靠的技术来测量高温下的划痕硬度,以确保为高温应用正确选择材料。

使用摩擦仪的高温划痕硬度