High temperature creep characteristics of molybdenum plates

Release time:

2024-12-06

High-temperature molybdenum plates are a type of high-temperature resistant metal material primarily composed of molybdenum, widely used in high-temperature environments such as aerospace, nuclear industry, and high-temperature furnace equipment. The following is an analysis of its high-temperature creep characteristics.

High-temperature creep characteristics

Creep is the phenomenon of materials slowly deforming over time under high temperature and constant stress conditions. The high-temperature creep characteristics of molybdenum plates are as follows:

1.Strong high-temperature stability

Molybdenum has a melting point as high as2623°C, and under high-temperature conditions of 1000~2000°C, molybdenum plates can still maintain good mechanical properties, resulting in a low creep rate.

2.Creep behavior stages

The high-temperature creep of molybdenum plates is usually divided into the following three stages:

Initial creep stage: The deformation rate is relatively fast but gradually slows down. It is mainly related to grain boundary sliding and dislocation movement.
Steady-state creep stage: The deformation rate is stable, which is the most important stage in long-term high-temperature use, significantly influenced by the microstructure and environmental conditions.
Accelerated creep stage: Grain coarsening and the formation of microcracks within the material ultimately lead to failure.

3.Micro-mechanisms

Grain boundary sliding: Deformation is caused by atomic migration or sliding at the grain boundaries.
Dislocation climb and cross-slip: The movement of dislocations is an important deformation mechanism for molybdenum plates under high-temperature conditions.
Diffusion creep: At high temperatures, atoms diffuse through the lattice or grain boundaries, leading to overall deformation.

4.The role of alloying and microstructure optimization

By adding a small amount of rare earth elements (such as titanium, zirconium, or rare earth oxides), the grain size can be refined, enhancing the high-temperature creep resistance of molybdenum plates. For example:

Titanium-zirconium-molybdenum alloy (TZM alloy): Adding small amounts of titanium and zirconium to molybdenum improves creep resistance and high-temperature strength.
Yttrium oxide reinforced molybdenum alloy: Refines particles and enhances grain boundary stability.

Creep failure analysis

In high-temperature environments, molybdenum plates may experience creep failure due to the following reasons:

Grain coarsening: Grain growth at high temperatures reduces the resistance to grain boundary sliding.
Microcrack formation: Stress concentration leads to the propagation of microcracks, ultimately causing fracture.
Oxidation: Molybdenum is prone to oxidation in high-temperature air, forming a brittle oxide layer (It is recommended to use zirconia ceramics), which exacerbates creep failure.

Engineering application recommendations

Environmental control: Use in inert gas or vacuum environments to avoid oxidation-induced creep failure.
Alloy optimization: Select appropriate molybdenum alloys (such asTZM) to improve high-temperature creep performance.
Design redundancy: Design the size and shape of molybdenum plates reasonably based on the required operating temperature and lifespan to avoid excessive stress concentration.

By selecting appropriate materials and optimizing usage conditions, the impact of high-temperature creep on the performance of molybdenum plates can be effectively reduced.

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