Heat treatment of nickel based alloy composite plates

　　There are many similarities between the heat treatment of nickel based alloy composite plates and that of austenitic stainless steel composite plates. Firstly, it is necessary to consider both the microstructure, state, and performance characteristics of the substrate and composite materials. Secondly, the influence of heat treatment on the strength of the bonding interface should be considered. The heat treatment of nickel based alloy composite plates has certain particularity. The solution treatment temperature of nickel based alloy itself is very high and requires a fast cooling rate. Within the range of normalizing temperature for carbon steel substrates, most nickel based alloys are heavily sensitized and precipitate various intermetallic compounds, reducing the corrosion resistance of nickel based alloys.

　　Nickel based alloy composite plates based on carbon steel and low alloy steel are mostly subjected to stress relieving heat treatment in order to balance the mechanical properties of the substrate and the corrosion resistance of the composite. The heat treatment method of stainless steel is similar to that of nickel based alloys, therefore, there is another option for the heat treatment of nickel based alloy composite plates based on stainless steel, which is solid solution treatment.

　　Below is a brief introduction to several heat treatment methods for nickel based alloy composite plates.

　　a. Heat Treatment of Hastelloy C-276 Composite Plate

　　The solid solution temperature of C-276 alloy introduced in the data is between 1150 and 1175 ℃. From Figure 2, it can be seen that C-276 alloy begins to sensitize within a short period of time within the temperature range of 700~1050 ℃. Therefore, the C-276 composite plate should undergo stress relief heat treatment below 700 ℃ as much as possible. If stainless steel is used as the substrate, high-temperature solid solution treatment can also be chosen.

　　b. Heat Treatment of Incoloy 825 Composite Plate

　　According to information, the heat treatment temperature range of 825 alloy is 920-980 ℃, with the most suitable temperature being 940 ± 10 ℃. Rapid cooling ensures the corrosion resistance of the material.

　　The base materials that can be combined with 825 alloy include C-Mn steel, Cr Mo steel, and stainless steel. Composite plates based on C-Mn steel and stainless steel can directly adopt the recommended heat treatment process of 825 alloy. Composite plates made of Cr Mo steel can be normalized, tempered, or tempered. The recommended heat treatment process for normalizing is 825 alloy, while the recommended tempering process is 700 ± 10 ℃ for rapid cooling.

　　c. Heat Treatment of Inconel 625 Composite Plate

　　The sensitization time of 625 alloy is relatively long, and it is not easy to undergo sensitization under normal heat treatment conditions. Therefore, the heat treatment of 625 composite plates can be normalized or stress relieved. Composite plates made of stainless steel can choose between solid solution treatment or stress relieving heat treatment. Inconel

　　After heat treatment at 1000 ℃, the 625+Q345R composite plate can achieve good mechanical properties and corrosion resistance.

　　With the increasing requirements for the use of various equipment, more and more nickel based alloy composite plates are being applied. During the manufacturing process of composite plates, it is necessary to pay special attention to the quality control of heat treatment. In the manufacturing process of nickel based alloy composite plates, appropriate heat treatment processes should be selected based on the characteristics of the laminated nickel based alloy, corrosion performance requirements, and the characteristics of the composite plate itself. Practice has shown that an appropriate heat treatment process can not only eliminate the stress generated during the explosion process to the greatest extent, restore and improve the mechanical properties of the substrate, but also ensure the corrosion resistance of the laminated nickel based alloy.



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