Influence of spraying parameters on diamond decomposition of HVOF sprayed nickel-diamond coatings

Diamond is the hardest known material and hence opens up a large, diverse field of applications for industrial processing tools. For these tools, different types of diamonds are used. For example large diamonds are frequently used to industrially process minerals while fine diamonds are used to process glass or carbon fibre reinforced plastic as well as for grinding and lapping.

A main challenge when processing diamonds is the process temperature. Diamonds show decomposition effects at higher temperatures. Therefore, the thermal spray process is investigated as an alternative processing method for diamond-reinforced coatings. Advantages of this process are the low thermal influence on the diamond, due to the short dwelling time of the particles in the flame and the flexibility regarding the application process of contour accurate coatings.

This paper gives an insight into the relationship between spray process parameters and the diamond decomposition concerning the particle temperature during the spraying process. For this purpose, the process parameters are varied, the resulting coatings are characterized, and the influence on the diamonds in the coating is analyzed. One focus of this paper is the investigation of thermally induced carbonating of the diamonds by using Raman spectroscopy and scanning electron microscopy.