- From sprue removal to deburring work: our ceramic grain abrasives achieve high stock removal in a short space of time
- Our proven silicon carbide abrasive formulation is especially suited to titanium surface grinding
- Whatever the turbine – aircraft, gas or water – VSM offers a broad portfolio of abrasive belt and disc products ranging from coarse to fine
- In turbine grinding, structural changes or microfissuring due to heat input are real showstoppers
- With the geometrically shaped VSM ACTIROX abrasive grain, less heat is generated automatically, as a result of short contact times and a faster cut
- Maximum stock removal over time is also guaranteed with VSM CERAMICS in combination with TOP SIZE – with reduced heat input
Turbine blades: high precision work
The engine of an Airbus A-380 is an impressive work of art, designed for high performance. 20,000 individual parts, 6.5 tonnes in weight, and with full thrust, the temperatures in the combustion chambers rise to over 2,000 degrees. They have to be able to withstand that. In order to cope with these extreme temperatures, some of which can even cause them to anneal, as well as strong tensile loads and vibrations, the turbine blades are made of highly durable and long-lasting materials: Titanium alloys, nickel-based superalloys and tungsten-molybdenum alloys. 100% flawless work must be carried out here, with exceptional surface quality, maximum precision and dimensional accuracy. The industry for grinding engine components is therefore one of the most demanding market segments of all.
Air, gas and water turbines
Titanium turbine blades are primarily used by the aircraft industry in aircraft engines. The other relevant market is that of industrial gas turbines, usually manufactured from Inconel, which are used for power generation, but also as mechanical drive machines. The smallest stainless steel turbines on the market can be found in water turbines, which are used in recreational areas (pools, swimming pools) or for smaller hydropower plants, for example.
To further enhance their thermal resistance and resistance to wear and tear, a coating is often applied to titanium or Inconel turbine blades. However, these material properties pose particular challenges for machining, which VSM meets with its Ceramics and Compactgrain series. Titanium, which is around half the weight of steel, has a high strength and very good corrosion resistance in certain alloys. But under the influence of temperature, it is very sensitive and quickly becomes brittle. Due to the high pressure at the grain tip, there is a tendency for strain hardening and plastic deformation during machining. It is therefore necessary to work with sharp tools and at the correct cutting speed. Titanium is around 30 times more expensive than conventional steel due to the complicated manufacturing process.
Inconel, a high-temperature nickel-based alloy that is predominantly used in the gas turbine industry, is also very difficult to machine. But it can also be found in the oil and gas industry as well as in medical technology. The main benefits are good retention of strength and hardness at high temperatures and excellent corrosion resistance. In combination with chromium, manganese and other alloys, however, Inconel is extremely difficult to machine. The material is very tough and also there is also a tendency for strain hardening during cutting due to the high pressure at the grain tip. Sharp grain types and cool cutting are therefore also recommended here.
Special processing features
Curved surfaces and many hard-to-reach parts – grinding is therefore the first choice when manufacturing turbine blades. The greatest challenge in grinding is the heat generated in the grinding process, both for titanium and Inconel. Titanium for example, is extremely sensitive to heat. It must therefore not heat up too much, as it is a very poor heat conductor. The high concentration of heat fom machining in the chip formation zone otherwise leads to micro or stress cracks. There is also the inherently difficult machinability of titanium and Inconel. It is therefore particularly important to optimise abrasives and grinding parameters, i.e. to find the ideal combination of abrasives and machine settings.
Grinding tasks from coarse to fine
Machining of turbine blades primarily involves working on welds and sprues, deburring, chamfering and fabricating or restoring specified surface structures. For this kind of machining, the self-sharpening ceramic grain abrasive belts from the VSM Ceramics and VSM Ceramics Plus series are recommended. They ensure high stock removal in the shortest possible time and the additional grinding-active layer top size significantly lowers the temperature in the grinding zone. VSM Actirox, with its geometrically shaped abrasive grains and optimised self-sharpening effect, delivers particularly quick results and increased grinding performance with maximum stock removal. We recommend our silicon carbide abrasives especially for surface grinding.
Grinding processes and use of machines
Backstands, known as sanding blocks, are usually used for machine processing of turbine blades. In addition to traditional manual hand grinding, these are also stationary machines that are mainly operated by robots. Depending on the size of the workpiece, the grinding unit is either guided over the workpiece – or the robot guides the blade to the grinding block. Alternatively, “hand power tools” such as angle grinders, dynafile grinders, drum grinders and others are also used.
Different manufacturing and repair requirements
Abrasives must meet a wide range of requirements in the production and repair of turbine blades. In simple terms, production involves machining cast or forged parts that are ground in their raw state in order to achieve a finished surface or to produce a certain dimension, in accordance with the drawing. In addition to VSM ceramic grain abrasives, VSM silicon carbide is also used here, which achieves a particularly fine scratch pattern.
During repair, on the other hand, the used turbine blades are X-rayed for damage and then welded. The main task during grinding here is the post-treatment of the welding work in order to return the workpiece to the required dimension. It is therefore mainly a question of removing weld seams and treating surfaces without creating micro-cracks. VSM ceramic grain abrasives are also the ideal choice here – from VSM Ceramics to VSM Actirox.