Chun & Vollerin: processing of semifinished products in Nickel Alloys, Duplex and Superduplex Alloys used in special enviroments such as high temperatures and high corrosion.
Chun & Vollerin provides for the marketing and processing of:
- Sheets and bars in nickel alloys and super alloys resistant to corrosion and high temperatures
- Copper Nickel alloys resistant to flowing clean seawater
- Cupronichel sheets and discs for tube plates
- Copper alloy tubes for heat exchangers
- Tubes for rolling
- Special tungsten materials for motor industry
- Welding materials
CORROSION RESISTANT ALLOYS
Maximum ability to withstand corrosion
Nickel and nickel alloys, have useful resistance to a wide variety of aqueous corrosive environemnts typically encountered in the chemical process industry and energy technology.
Nickel by itself is a versatile corrosion resistant metal. More importantly, its metallurgical compatibility over a considerable composition range with a number of other metals as alloying elements has become the basis for many binary, ternary and other complex nickel alloy system, having very unique and specific corrosion resistant behaviour for handling modern day corrosive environments of the chemical process industry.
Corrosion resistant depends on the chemical composition of the alloy, the alloy's micro-structural features, the chemical nature of the environment and the nature of the alloy / environment interface.
The main alloying element is chromium, which is necessary for a stable passive surface layer, upon which the corrosion resistance depends. After chromium, molybdenum is the most important alloying element by increasing the resistance to general corrosive attack in reducing media. Together with chromium it is of paramount importance for pitting and crevice corrosion resistance.
HEAT RESISTANT, HIGH-TEMPERATURE, HIGH-STRENGTH
Heat-resistant alloys are characterized by their specific resistance to the attack of hot gases and combustion products above 550° C (1,022° F). This specific resistance requires the formation of protective oxide layers on the surface. Of the three elements aluminium, silicon and chromium wich can be used for the formation of the protective oxide layers, chromium can be used most universally. However, aluminium has to be used for service temperatures in oxidizing atmospheres above 1,000° C (1,832° F).
The addition of small amounts of yttrium and of rare earth elements, e.g. cerium increases the adhesive strength of the protectiveoxide layer. Addition of silicon is effective, mainly in the initial stages of oxidation, as it contributes to a very rapid oxide film formation. Increasing nickel content produces increasing resistance to uniformly carburizing gases but has a more detrimental effect with regard to resistance to sulphur bearing media.
High-temperature high-strength materials have outstanding mechanical properties at high temperatures under long-term loading; this implies high resistance to creep and a high creep rupture strngth, even at temperatures above approximately 550° C (1,022° F). However, in many applications high-temperature-high-strength properties and specific resistance to the attack of hot gases and combustion products above 550° C (1,022° F), i.e. heat resistance as defined above, are required simultaneously.