"The trick is to bring the characteristics of the material through the production process into the finished structural component," explains Esser, who has already come up with 53 inventions for his employer in his capacity as a development engineer with Siemens Energy in Mülheim an der Ruhr. Esser holds 55 patents altogether. Previously, gas turbine blades were produced as so-called single-crystal components, but these were very prone to faults and expensive owing to the high reject rate. There was no alloy in the world that was capable of meeting the high quality requirements associated with large blades such as the ones that drive the Siemens A2 gas turbines.

So Esser’s team decided to work with a completely new alloy for which there had been no ideal production process up till then. It was the team’s job to discover just such a process. The alloy itself, called SieMet, originated with Howmet, one of Siemens’ partner companies based in Hampton, Virginia, USA. In fact, Siemens maintains a development office there in order to speed up the consultation process when staff members from the two partner companies are involved in development programs.

The cast blades must be reheated and then cooled in a controlled process so that the metal homogenizes and acquires optimal stability. The technical term for this is "solution annealing." "We couldn’t employ the normal temperature and timing for the solution annealing process, because when we did that the blades developed cracks," says Esser. The idea was to stop producing blades made from the new alloy in a single-crystal process and instead to produce them by means of the so-called directionally solidified process. During a single-crystal process all the atoms are arranged in a uniform lattice; however, in the directional process the grains of metal solidify in a particular direction, namely in the direction in which the centrifugal force will eventually act upon the operational blade. As a result, there will be no cracks in the blade. This technique produces significantly fewer rejects and thus reduces costs considerably.

"We discovered that the cracks only appeared at high temperatures," reports Esser. A further difficulty was that the metal must not be allowed to crack as a result of the cooling process that makes the casting core contract, thereby giving rise to the cavity in the blade. Gradually the team evolved a casting process that included solution annealing at reduced temperatures, which produced the optimal result and was suitable for use in production planning at the Siemens gas turbine plant in Berlin.

For years, Esser has possessed expert knowledge in the area of metals. He studied mechanical engineering at the University of Bochum and received his doctorate in materials science. He is now 58, and has worked for Siemens since 1981.