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There are many surface treatments used to improve some properties when manufacturing metal parts. The QPQ treatment is one of them, especially to improve the properties of the surface of the metal part.
Here you will learn everything you need to know about QPQ coating.
QPQ stands for “Quench Polish Quench”. It refers to a process used to increase corrosion resistance.
Yet, other properties can be improved by performing the QPQ treatment, including:
The QPQ coating offers several benefits. First of all, it improves the properties mentioned above.
Also, for many industries and applications, it is essential to increase corrosion resistance. So, quench polish quench becomes a very helpful treatment for them.
Some of the most relevant advantages of applying QPQ treatment include:
Unfortunately, the QPQ coating is not a perfect process.
The QPQ treatment will help you improve those properties you need. But, there are a few drawbacks to consider.
The most important disadvantages of QPQ coating are:
Several materials can be treated by applying the QPQ coating.
Ferrous materials are the most commonly treated by this process. This is because it is mainly used to improve corrosion resistance.
That said, here are some of the QPQ coating applicable materials:
A few tests have proved that the QPQ process may reduce the corrosion resistance of some stainless steels. So, caution is needed with this material.
Many applications can benefit from a treatment like QPQ coating.
Many industries want their products to be stronger and more durable. So, they may find the QPQ process very attractive.
Common industries that take the benefits provided by the QPQ treatment include:
Therefore, common application examples are:
The QPQ process is performed in three steps. Also, it requires high temperature, mechanical processing, and chemical reactions.
Like with any other treatment, precise control of important parameters is necessary.
There are many other processes used to treat metal parts which are like QPQ Coating. Among the most popular ones, we can find Nitride, DLC Coating, and Black Oxidize.
The main similarity is that they are all used to improve the properties of the finished part. However, there are many other similarities.
For example, Nitride is similar to QPQ Coating in the fact that both are considered case hardening processes. DLC Coating is used to increase wear resistance and lubricity. Meanwhile, black oxidized is used to increase corrosion resistance. Clearly, they are similar, so the question is what makes them different?
While both QPQ coating and Nitride create a layer of ε iron nitride on the material, they are not the same.
They both indeed belong to the group of thermochemical heat treatments. Yet, there are important differences in parameters. These are the temperature used, the completion time, and the steps to complete the process.
Take look at the table to better understand how these two processes compare.
|Hardness||HRC60 – HRC70||HRC14 – HRC65|
|Thickness||0.04mm – 0.45mm||0.0127mm – 0.6096mm|
|Temperature||480°C – 630°C||400°C – 590°C|
|Completion time||30 min – 5 hours||Up to 90 hours|
The most obvious difference between the QPQ Coating and DLC coating is the appearance of the surface treated.
Diamond-Like Carbon (DLC) coating results in a very reflective polished surface. This result makes it different from the QPQ Coating since it results in a more “mate-like” surface finish.
Other differences can be seen more clearly in the table below.
|Parameter||QPQ Coating||DLC Coating|
|Hardness||HRC60 – HRC70||1200HV – 7000HV|
|Thickness||0.04mm – 0.45mm||1µm – 10µm|
|Temperature||480°C – 630°C||<200°C|
|Completion time||30 min – 5 hours||From minutes to hours depending on part sizes|
The Black Oxidized process can be performed at different temperatures. This is an obvious difference with QPQ coating. The different temperatures make the process take different names. Such names are hot black oxidized, mid-temperature black oxidized, and cold black oxidized.
Another big difference is that Black Oxidized can be applied to non-ferrous materials such as copper and zinc.
Even so, the most important difference is that Black Oxidized does not increase the hardness of the part. Black Oxidized treatment only provides corrosion resistance, reduced light reflection, and desired appearance.
For a better view of other differences, take a look at the table below.
|Parameter||QPQ Coating||Black Oxidized|
|Hardness||HRC60 – HRC70||N/A|
|Thickness||0.04mm – 0.45mm||<1µm|
|Temperature||480°C – 630°C||Room temperature (cold), 104°C -118°C (mid-temperature), 141°C (hot)|
|Completion time||30 min – 5 hours||From minutes to hours depending on part size|
Quench Polish Quench or QPQ coating is a sophisticated heat treatment for ferrous metals such as steels and iron.
The main idea to use the QPQ process is to achieve very high corrosion resistance and lubricity. This makes it ideal for many different applications.
Besides, keep in mind that QPQ treatment is an environmentally friendly process. Also, it provides low distortion results.
And of course, there are many other advantages that you can get which were described above.
However, the QPQ coating is limited to ferrous materials. So, if you are thinking about treating other types of material, you may want to look for a different process.
You must also consider your budget. Higher energy consumption and the equipment required make it more expensive than others.
It is up to you to choose the surface treatment. Yet, the recommendation is to always consult with an expert. This way you can make sure you are investing your money wisely.
And you can get the help you need right here. Contact us at firstname.lastname@example.org and get the expert consultation you need.
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