#alloys

Self-Healing Ceramic Coating Seals Turbine Cracks at 800 °C

Inspired by natural glaze layers in cobalt superalloys, the new coating uses cobalt oxide migration to fill cracks, limit spallation, and protect extreme-environment engine components from heat-driven damage. In a recent research article available as an Article in Press in the journal Communications Materials, researchers developed a self-healing ceramic coating based on phase segregation in the CoO–Cr2O3 system that autonomously repairs thermally induced cracks at elevated temperatures, enhancing durability and lubricity for gas turbine engine applications. Extreme Environment Material Challenges Gas turbine engines experience extreme thermal and mechanical stresses, with surfaces exposed to temperature gradients that can reach 2000 °C, leading to material degradation through cracking and wear. Enhancing surface durability is essential for improving engine efficiency and meeting environmental targets.

What is the difference between welding, brazing, and soldering?

A summary of the main points of difference between welding, brazing, and soldering are:

1. Temperature Range:

Welding: Above 1,200°C.

Brazing: From 450°C to 1,100°C.

Soldering: Below 450°C.

2. Strength of Joints:

Welding: Highest.

Brazing: Moderate.

Soldering: Lowest.

3. Applications:

Welding: Heavy-duty construction, automotive, aerospace.

Brazing: HVAC, electrical, automotive.

Soldering: Electronics, plumbing, jewelry.

4. Process complexity:

Welding: Requires high skill and complex equipment.

Brazing: Moderate skill and equipment.

You have probably heard the word alloy before but may not know exactly what that means. An alloy is a mixture of two or more chemical elements, often with at least one metallic element.

The mechanical properties of alloys will often be quite different from those of its individual constituents. This is very important, as alloys are made in an attempt to bring out the best characteristics of the different pieces. For example, both aluminum and copper are very soft metals but when melted together the resulting alloy is much stronger.

By adding a little bit of carbon to iron you create the alloy steel which makes it highly ductile and higher resistance to corrosion making it one of the mostly widely used alloys.

Copper/tin alloys bronze and copper/zinc alloy brass have been used for centuries due to their low melting points.

Amalgams, alloys made with mercury which can dissolve many metals, has been used in Chinese gilding for many centuries as well.

Many alloys are man made, but there are naturally occurring alloys such as meteoric iron (iron and nickel),

electrum or white gold (gold and silver),

and bronze.

Can you think of any other alloys?