Moving and fixed blades for steam and gas turbines are very important elements. They sufficiently affect the reliability and efficiency of the whole turbine. Moving blades are subjected to high rotational speeds and strenuous environment of steam and gas flow, which invoke intense dynamic and temperature stress inside the blades, including vibration load.Many steam turbine blades work in steam of high temperature, some of them work in steam of different levels of humidity.Gas turbine blades work at high temperatures over 1000ºC.
Such conditions and requirements make it necessary to use heat-resistant and stainless steels, for example, 18H11MFNB-sh,15H11MF-sh, 20H13-sh, etc. and also alloys containing over 65% of nickel, for example, HN65KMVUB (EP-800-VD) for producing blading systems. It affects the cost of blade production making it a significant part of the whole turbine cost (about 25-30%).
Metal roll (squares and bars) and stamp blanks are used for production of blades.
Percentage of metal used in production of blades from metal roll is 10 – 15%.Blades made from stamp blanks have high percentage of metal use and save labour costs during the machining.
Blades are machined on modern OKUMA's (Japan), C.B.Ferrari's (Italy) 4- and 5-axis milling machining centers with the use of hard-alloyed tools produced by the leading foreign manufacturers.Accuracy of blades production is checked on DEA's (Italy) inspection and measuring machine.
At present, steam and gas turbine blades are manufactured from stamp blanks up to 550 mm long and up to 3.6 kg and from metal roll up to 400 mm long and up to 2 kg.
The minimal length of the manufactured blades is 55 mm, the minimal weight is 0.10 kg.
Also the production of blades from titanium alloy VT-8 for aircraft engines was mastered. The maximum length of a blade is 700 mm.
The blades are produced for steam turbines with power capacity of 25-1000 MW used at thermal and nuclear power stations, and also for gas turbines used at gas compressor stations.