subject: Wear Coatings For Die Casting [print this page] Companies that make or use die castings during their daily production/ manufacturing know the importance of treating the die castings with wear coatings. It's common practice to fabricate die castings out of aluminum and magnesium metals. These metals can have a decreased hardness compared to other metals used in die castings, which makes the practice of treating the castings with wear coatings an important one. Applying wear coatings to die castings helps to prolong the life-expectancy of the castings, which in turn, allows the company to produce more castings from a single die.
Applying coatings to dies can especially improve a problem known as heat checking. Heat checking can be greatly reduced when wear coatings are applied from the beginning of the die's life. Prolonging the life of a single die translates into higher profits for the company, because the die is being used more heavily.
The process known as heat checking is a common reason that dies fail. It occurs when over stressing of the metals/ thermal fatigue happens to the dies. Dies are repeatedly heated and cooled over long periods of time. This alternate process and drastic change in temperatures causes fine cracks to appear in the die, which over time, can weaken dies and cause problems when casting. Applying wear coatings as pretreatments adds strength to the metal dies and helps to improve and prevent preexisting damage done by heat checking. Although wear coatings will not remove heat checks in their entirety, they will reduce the relentless damage that has been caused, and in turn, slow down the heat checking process.
During die casting, the alternate process of heating and cooling the metal die often results in severe wear over time. Heat energy is transferred to the die by passing through the metal and heating it rapidly. Once the rapid heating has ceased, it is then quickly cooled. This alternate process is the direct cause of heat checking; a process that occurs over a period of time and can go undetected. The fine cracks will lengthen and penetrate the metal die deeper if the die is not checked repeatedly. If left unchecked, the die may have severe heat checking which could result in costly repairs or die replacement.
By taking action at the first sign of heat checking, the life expectancy of dies can be drastically prolonged. This process of applying wear coatings to dies is not once and done. The applications must be done over the course of the die's lifetime in order to insure maximum performance and to minimize the effects of heat checking.
Once wear coatings are applied to dies that presented signs of heat checking, there will be one of two results. First, the coating will have filled the cracks and have smoothed the die surface. Second, the heat checks are severely reduce by wear coatings, but are not removed in their entirety as in the first instance. This happens because the heat checks were not at their initial stages when the coating was applied, making it more difficult to restore the die's surface to its appearance prior to heat checks. Whether the die presents with mild or severe heat checking, the benefits of applying wear coatings far outweigh the negatives associated with it; which is often the cost of the wear coatings process.
