IN738LC 是一种重要的镍基超级合金，广泛用于制造燃气涡轮发动机的热段部件。它具有优异的高温机械性能和良好的加工性能。
本指南详细介绍了 IN738LC，包括其成分、特性、加工、应用、优势、局限性、供应商以及与其他超级合金的比较。
介绍 IN738LC 超级合金
IN738LC 是一种可沉淀硬化的镍基超级合金，具有以下主要特性：
- 出色的高温强度和抗蠕变性
- 良好的抗热疲劳和抗氧化性
- 可在 ~1100°C 温度下保持特性
- 成分经过优化，易于加工
- 在燃气轮机中的广泛应用
- 可提供板材、中厚板、棒材和锻件
- 可采用适当的技术进行焊接
其均衡的特性使 IN738LC 适用于在苛刻条件下工作的各种燃气轮机部件。
IN738LC 的化学成分
IN738LC 的标称化学成分为
IN738LC 化学成分
| 要素 | 重量 % |
|---|---|
| 镍 | 巴尔 |
| 铬 | 16.0 |
| 钴 | 8.5 |
| 铝质 | 3.4 |
| 钛 | 3.4 |
| 钽 | 1.7 |
| 碳 | 0.11 |
| 硼 | 0.001 |
- 镍提供基体并提高延展性
- 抗热腐蚀和氧化的铬
- 用于强化的难熔元素，如 Ta、Ti、W
- 用于晶界强化的碳/硼
- 优化成分，提高焊接性
平衡合金设计兼具高温强度、延展性和可制造性。
IN738LC 的物理和机械特性
物理特性
- 密度：8.19 克/立方厘米
- 熔化范围1315-1370°C
- 导热系数：11 W/m-K
- 弹性模量：205 GPa
- 电阻率： 125 μΩ-cm
室温下的机械性能
- 拉伸强度： 1035 兆帕
- 0.2% 屈服强度：965 兆帕
- 伸长率：22%
- 疲劳强度：590 兆帕
高温机械性能
- 拉伸强度
- 704°C 时 750 兆帕
- 982°C 时为 255 兆帕
- 断裂强度：
- 760°C 时 240 兆帕（100 小时）
- 982°C 时 170 兆帕（100 小时）
这些特性使其适用于温度高达 ~9500C 的长期使用，并具有适当的设计余量。
IN738LC 超级合金的主要应用
IN738LC 适用于
- 燃气轮机热段部件：
- 燃烧器内衬
- 过渡管道
- 涡轮喷嘴
- 1 级和 2 级涡轮叶片和叶片
- 火箭发动机燃烧室
- 热处理装置
- Nuclear fuel rods
- Chemical process industry components
Its versatility makes it useful across several critical high temperature applications in demanding environments.
Manufacturing and Processing of IN738LC
Important manufacturing aspects for IN738LC include:
融化
- Vacuum induction melting and vacuum arc remelting
- Ensures chemical homogeneity
Forming
- Hot working above 1150°C
- Cold working for sheet and foils
热处理
- Solution treatment – 1120°C, fast cooled
- Precipitation hardening – 845°C, 24 hours, air cooled
加入
- Electron beam and vacuum brazing
- Fusion welding using matching filler alloys
涂料
- Diffusion aluminide and overlay coatings
- Thermal barrier coatings
Control of melting, hot working, heat treatment, joining and coatings is critical to achieve optimal properties.
Why Choose IN738LC Superalloy?
Some key advantages of IN738LC:
- 优异的高温机械性能
- Retains strength and creep resistance upto ~1100°C
- 良好的抗热疲劳和抗氧化性
- Better processing flexibility versus other Ni-superalloys
- Can be fused welded for fabricating complex parts
- Available as sheet, plate, bar and forgings
- Cost-effective compared to contemporary alloys
- Established processing methods and data available
- Approved for critical engine components
The balanced properties and processability of IN738LC make it an ideal choice for many gas turbine hot section components.
Limitations of Using IN738LC Superalloy
Some limitations to consider while using IN738LC are:
- Lower high temperature strength than latest single crystal alloys
- Not suitable for very high temperature turbine parts
- Susceptible to strain-age cracking during forming
- Requires carefully controlled heat treatment
- Lower oxidation resistance than Nb-bearing alloys
- Weldability not as good as IN718
- Forming can induce residual stresses
IN738LC may not be suitable for very demanding environments. Proper design and processing is key to mitigate limitations.
IN738LC Superalloy Suppliers
Some leading suppliers of IN738LC alloys include:
- Special Metals Corporation
- Allegheny Technologies
- Haynes International
- 木匠技术
- 山特维克材料技术
- Precision Castparts Corp.
IN738LC is available as:
- Sheet / Plate
- Bar
- Forging stock
- Wire
- Welding consumables
Various product forms are offered to suit different fabrication requirements.
IN738LC Superalloy Costs
IN738LC Cost Indicators
- Sheet: $90-110/kg
- Bar: $100-120/kg
- Forging stock: $110-130/kg
- Costs depend on size, quantity, supplier, and raw material costs
- Generally 10-15% economical than contemporary Ni-alloys
- Requires high purity raw materials increasing costs
IN738LC provides cost-effective performance for many gas turbine applications. Long term agreements can secure stable pricing.
Comparison of IN738LC with Alternative Superalloys
Comparison with IN718
- IN738LC has higher temperature capability
- Better creep and thermal fatigue properties
- Reduced forming issues versus IN718
- IN718 offers better weldability
Comparison with IN713C
- IN738LC has higher tensile and creep strength
- Improved phase stability
- Lower expansion coefficient than IN713C
- IN713C offers better fabricability
Comparison with Contemporary Ni-Alloys
- Advanced alloys like Renes N5, CMSX-4 offer higher temperature strength
- However, they also have poorer fabricability and higher costs
- IN738LC provides a cost-effective combination of properties
常见问题
Q: What are the main applications of IN738LC alloy?
A: Main applications are gas turbine hot section parts like combustors, transition ducts, nozzles, turbine vanes and blades. It is also used in rocket engines and nuclear fuel rods.
Q: What are the key properties of IN738LC?
A: It has excellent high temperature mechanical properties upto 1100°C, good fatigue and oxidation resistance, high strength, and better fabricability than other Ni-superalloys.
Q: What heat treatment is used for IN738LC?
A: Solution treatment at 1120°C followed by precipitation hardening at 845°C/24 hrs. Controlled heat treatment is critical to achieve required properties.
Q: How is IN738LC welded?
A: Electron beam and vacuum brazing are commonly employed. Fusion welding can also be done using matching filler alloys and carefully controlled processes.
Q: What are the alternatives to IN738LC?
A: Alternatives include IN718, IN713C and advanced Ni-alloys like Renes N5, CMSX. Each has relative pros and cons versus IN738LC.
Q: Does IN738LC need coatings?
A: Diffusion aluminide or overlay coatings may be used. Thermal barrier coatings are beneficial for turbine components. Coatings enhance oxidation and corrosion resistance.
Q: What precautions are needed when machining IN738LC?
A: It requires high cutting speeds with sharp tooling to avoid work hardening effects. Generous coolant is essential. Machining can induce residual stresses needing relief heat treatment.
Q: Where is IN738LC used in gas turbine engines?
A: It is widely used for combustion liners, transition ducts, nozzles, stage 1 and 2 turbine vanes and blades in the hot sections.
Q: What forms is IN738LC available in?
A: Common product forms include sheet, plate, bar, forgings, wire. Various forms are used to fabricate hot section components based on requirements.
