New Thoughts On Hydrogen Embrittlement Of 10.9 Bolts

Recently the International Organization for Standardization, known as ISO put out a new technical report relating to hydrogen embrittlement. Hydrogen embrittlement of fasteners is often something that many customers will be discussing ahead of time. Much like with most potential problems that you might face as a result of your fasteners, hydrogen embrittlement of 10.9 bolts is a complicated issue with ways in which you can potentially avoid it from taking place. This is why it is particularly important for people to understand what these terms mean in order to proceed with your fastener with confidence without worrying about it being destroyed in your hands.
When it comes to hydrogen embrittlement there are many things to consider, from the types of hydrogen embrittlement to the manufacturing process, to testing. All these different aspects are part of ensuring that your fastener is in the best possible condition and will continue to hold strong over time. Especially in projects that require 10.9 bolts, this can be particularly important as any mistake can end up being very costly.

 

 

What is Hydrogen Embrittlement?

Hydrogen embrittlement, at times referred to as HE is the deterioration of the structural properties of metals because of the existence of hydrogen. Hydrogen embrittlement can occur in multiple different forms. Most commonly tensile stress along with the hydrogen that dissolved in the metal is enough to cause hydrogen embrittlement. Different materials might have different chances of having to go through hydrogen embrittlement. This is why it is important to know the material you are using and how they interact with the space around them in order to determine which material would serve the best for your project.

 

 

What is a 10.9 bolt?

A Grade 10.9 bolt is the type of bolt that is most commonly used in the automotive industry. Some will refer to these bolts as “car bolts.” In terms of material, they are constructed of boron or carbon steel and are particularly well known for their tensile strength.

 

 

What does the grade in a bolt show?

 

The bolt grade shows the maximum amount of stress, or tensile stress, that the bolt can handle without being destroyed or breaking. For example, a 10.9 bolt is much stronger than an 8.8 bolt. The strength of this bolt and its ability to easily handle high amounts of stress while also being able to avoid corrosion because of the high-quality material is on most occasions the reason why bolt 10.9 is used in the automotive industry.
If you are searching for high-quality 10.9 bolts in different materials then the best place to look is AYA fasteners. AYA fasteners guarantee not only quality but also incredible fasteners that will help you secure every project you have in every location you need. To learn more about the different options offered by AYA fasteners, you can visit our website.

 

 

Is it a problem if my 10.9 bolts are experiencing hydrogen embrittlement?

Fasteners sustaining hydrogen embrittlement (HE) will be affected by permanent loss of ductility. This is because of the atomic hydrogen coupled with tensile stress which can really affect the metals and their way of connection. This is a particularly big risk as it is possible for fasteners to fail completely after experiencing hydrogen embrittlement.

 

 

What significant points are raised in the ISO report about hydrogen embrittlement?

 

One of the most controversial aspects of that technical report is that for the first time, it appears to present 10.9 fasteners as not being significantly susceptible to hydrogen embrittlement failure. This is only in cases when the bolts have been manufactured with carefully selected and well-controlled steel. This is one of the reasons why it is particularly important to check the manufacturer when you are selecting where to buy your bolts from.
This approach is continuous in the newest version of the ISO 4042 standard (Fasteners: Electroplated coated systems) where 'baking' following plating is considered an option following the end of the verification.
Another important concern that is mentioned in the ISO report regarding bolts belonging to the property class of 10.9 that are experiencing environmental hydrogen embrittlement is that often times the blame is placed entirely on the manufacturer. In most of these cases where the fasteners fail within a few months, the fault is usually found to have been with the manufacturing process, which is why the manufacturer would be found to be at fault in cases of hydrogen embrittlement.
However, in environmental hydrogen embrittlement, the blame for something going wrong usually falls on the Engineer, as they are the ones to have selected either the wrong material or the wrong fastener grade. There is also a chance of having the application blamed.
In general, high-strength fasteners, have always been believed to be inherently susceptible to hydrogen embrittlement however with the report that changes slightly.
 

 

What are the two types of Hydrogen embrittlement?

 

There are two different distinct types of hydrogen embrittlement. These are:

1. Internal Hydrogen Embrittlement
This type of embrittlement occurs during the first phase of manufacturing and specifically during the type when the metal is cast into components. Internal hydrogen embrittlement means that atomic hydrogen has entered the molten metal and at times become supersaturated upon solidification. Once the excess hydrogen settles your material is likely going to be experiencing molecular irregularities, leading to compromised electrical and mechanical properties of all the components manufactured and affected by internal hydrogen embrittlement.

2. External Hydrogen Embrittlement
External hydrogen embrittlement is affected by environmental conditions which could lead to the metal being affected by the hydrogen being absorbed into the metal body. Generally, the environmental conditions need to be relatively extreme in order for external hydrogen embrittlement to take place. These include extreme heat, very long chemical treatments, electroplating, cathodic protection, operation in areas with high-pressure hydrogen, and corrosion.

 

 

Why is hydrogen embrittlement a problem?

 

Hydrogen embrittlement can actually be one of the costliest problems that one can encounter regardless of their industry. This is because in the case of a hydrogen embrittlement change you most likely are going to require a full product campaign change.

 

How can you prevent hydrogen embrittlement?

 

Some steps can be taken in order to reduce the chances that your steel bolts have been exposed to hydrogen. Most notably these steps include reducing hydrogen exposure and baking after electroplating. Specifically, baking hydrogen embrittlement of electroplated components needs to be done at 375 to 430 °F (190 to 220°C) within a few hours of the end of the electroplating process.

 

 

What is required for hydrogen embrittlement to cause failure?

There are three requirements for failure caused by hydrogen embrittlement. These are the following:

 

1. A susceptible material: specifically, any high-steel steels with high tensile strength are likely to be vulnerable to hydrogen embrittlement.
2. An environment where exposure to hydrogen is possible: this is why it is particularly important to ensure that there is no exposure to hydrogen when the surface is finished.
3. Tensile stress: in the case of embrittled material tensile stress can be the toe that broke the camel’s back. What that essentially means is that the stress could lead to the fastener permanently failing.

 

What are the methods for evaluating hydrogen embrittlement?

 

There are two different tests that you have to use if you want to evaluate whether the processing you have undertaken leads to steel hydrogen embrittlement. These are:
1. ASTM F1940 Standard Test Method for Process Control Verification to Prevent Hydrogen Embrittlement in Plated or Coated Fasteners
2. ASTM F519 Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating Processes and Service Environments

 

 

Conclusion:
Hydrogen embrittlement can be a particularly big problem because there are two different types. As a result, you are likely going to have to face either internal hydrogen embrittlement which is caused by poor manufacturing practices, or external hydrogen embrittlement which is affected by environmental factors. While there are techniques that can help reduce hydrogen embrittlement as well as tests that you can use to evaluate the process, the reality is that once something goes wrong with a component there is no immediate way to fix it. As such, the quality of the fasteners and 10.9 bolts being used in your projects are particularly important as good manufacturing practices can significantly reduce your chances of having to deal with hydrogen embrittlement.

 

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