Myth 2 about Thermal Spray

       Recently, I found that some customers have misunderstandings about coating, and I will share with you here.



1. The hardness of the coating is not enough



A customer hit the coating with a hammer, and then the coating was dented. The customer said, "The hardness of the coating is not good. It is impossible for the steel I quenched to be deformed. Hard enough."



A very important feature of thermal sprayed coatings is that they are very brittle. When I communicate with customers, I always remind customers that "the coating is not impact-resistant". The most suitable coating is friction and wear resistance, but if there is impact, corrosion, etc. at the same time as friction and wear, then it is necessary to carefully consider whether to use the spraying process. Because impact destroys the coating, corrosion then erodes the entire coating and product matrix from where it broke.



Tapping the coating with a hammer to deform it does not prove any problem. I have explained in detail how the hardness of the coating is judged before.



Here I give a very simple example:



We can break one chopstick by hand, but we cannot break 10 chopsticks at the same time, because the strength is different. Most of the coatings we spray are only about 0.2mm, so what if the thickness of the spray is 10mm? The author has sprayed the thickest coating up to 32mm, which is extremely hard, but even with such a thick coating, the brittleness has not changed, and it will still be broken when encountering a strong impact.



2. The coating is not wear-resistant



A customer recently used an angle grinder to grind the coating we sprayed, and then told me "the coating you make is not wear-resistant, and I can use an angle grinder to grind it off."



Later, I gave this client an example of "drops of water through the stone". I believe everyone understands this simple truth. There is nothing in this world that doesn't wear out. It doesn't wear out because the work is not enough. And there is another problem. The oxide layer on the surface of the coating is polished off, revealing the metallic color. This does not mean that the coating is gone. The tungsten carbide coating will become brighter after being polished. When many customers use it, if the coating is smooth, it means that the coating is gone. This analysis is very arbitrary. The only way is to use a spectrometer to analyze whether the coating is still there. .



     When we judge the hardness, wear resistance and corrosion resistance of the coating, we must use scientific methods to judge, so as to be justified, rather than judge by some methods that violate the rules. I have briefly explained some testing methods of coatings before. In order to make it easier for customers to choose coatings and test coatings, I will explain the hardness, porosity, bonding strength, toughness, wear resistance and corrosion resistance of coatings in detail later. Test methods for resistance, oxidation resistance, thermal shock resistance, etc.