Heat resistance of an alloy

It depends on the grain size and on the preferential distribution of impurities around the crystals. A buildup of impurities in the boundary volume that weakens the strong bond between the crystals can dramatically lower the heat resistance level.

Comparative steel properties

Coarse-grained steel has a higher degree of creep resistance than hot-rolled steel, which has a fine grain size in its base. In the test, the temperature level required for recrystallization was slightly exceeded. As a result, the coarse-grain steel showed less steep line slopes in the diagram. Considering the test results, we can draw the following conclusions. Fine-grained alloys, when tested at room temperature and at reduced temperature, have greater strength. At elevated temperatures the coarse-grained alloy has high heat resistance, but the plastic properties deteriorate. Such characteristics are also suitable for alloys with an austenitic structure and for alloys with a ferrite structure.

Effect of impurities

If there are impurities in the alloy, the grain size has a decisive influence. Harmful impurities that enter the boundary regions lower the heat resistance. When the alloy begins to solidify and crystallize, the impurities tend to accumulate in the boundary zone. This tendency is more pronounced in the cast material than in the deformed material. However, the deformed material also has weakened grain boundary strength at high temperature. The exception is the impurities of molybdenum, tungsten, niobium and other heat-resistant elements, whose additives in small amounts have a positive effect on the strength of the alloy, at high temperature.

Influence of the differentiated grain sizes

The heat resistance also decreases if a material has a mixed grain size. Only a sample with a homogeneous grain structure showed high heat resistance. If a specimen of heterograin composition is subjected to stress at high temperature, it can lead to cracking of the material at the grain boundary. Alloy with coarse grains is more heat resistant and practical. When materials of different specimens were tested for longevity, tears along the grain boundary were observed that had nothing to do with specimen fracture. The plastic properties of the material are greatly reduced by the second phase of testing.

Influence of surface quality

The nickel-plated specimens and those without such protection did not differ in strength tests. Material samples with a polished surface broke much later than samples that had a rough, untreated surface.

Effect of heat treatment

Overheating of steel forgings produces a reduction in heat resistance. Overheating causes structure coarsening and intergranular oxidation. The temperature conditions must be closely monitored. Hot-rolled and hot-formed materials, when aging gives a decrease in the heat resistance if the processing temperature is too high.

Buy, price

At the warehouse of Evek GmbH always in stock high-quality rolled metal products at the best prices. All batches of products have a quality certificate for compliance with the standards and technical conditions of operation. The certificate indicates the manufacturer, the number of drawings and part names, alloy grade, melting number, the mechanical properties of the parts, chemical composition and the results of additional tests. Orders are realized in the shortest possible time. Preferential discounts are offered to wholesale customers.