Hastelloy alloy special material properties and introduction

Hastelloy alloy special material properties and introduction

Hastelloy alloy

I. Introduction

Hastelloy is a type of nickel-based alloy. It is currently divided into three series: B, C, and G. It is mainly used for strong corrosion that cannot be used in iron-based Cr-Ni or Cr-Ni-Mo stainless steel, non-metallic materials, etc. It has been widely used in petroleum, chemical industry, environmental protection and many other fields abroad.

In order to improve the corrosion resistance and cold and hot working properties of Hastelloy, Hastelloy has made three major improvements. The development process is as follows:

B series: B → B-2(00Ni70Mo28) → B-3

C series: C → C-276(00Cr16Mo16W4) → C-4(00Cr16Mo16) → C-22 (00Cr22Mo13W3) → C-2000(00Cr20Mo16)

G series: G → G-3 (00Cr22Ni48Mo7Cu) → G-30 (00Cr30Ni48Mo7Cu)

The most widely used materials at present are N10665 (B-2), N10276 (C-276), N06022 (C-22), N06455 (C-4) and N06985 (G-3). The third generation materials N10675 (B-3), N10629 (B-4), and N06059 (C-59) are in the promotion stage. Due to the advancement of metallurgical technology, multiple brands of so-called "super stainless steel" containing ~6% Mo have appeared in recent years, replacing G series alloys, causing a rapid decline in the production and use of G series alloys.

2. Mechanical properties

The mechanical properties of Hastelloy are very outstanding. It has the characteristics of high strength and high toughness, so it is difficult to machine. Moreover, its strain hardening tendency is extremely strong. When the deformation rate reaches 15%, it is about 18-8 Twice that of stainless steel. Hastelloy also has a medium-temperature sensitization zone, and its sensitization tendency increases with the increase in deformation rate. When the temperature is high, Hastelloy easily absorbs harmful elements, causing its mechanical properties and corrosion resistance to decrease.

Hastelloy C-276 alloy (Hastelloy C-276 alloy)

1. Corrosion resistance

Hastelloy C-276 alloy is a nickel-molybdenum-chromium-iron-tungsten series nickel-based alloy. It is one of the most corrosion-resistant modern metal materials. Mainly resistant to wet chlorine, various oxidizing chlorides, chloride salt solutions, sulfuric acid and oxidizing salts, and has good corrosion resistance in low and medium temperature hydrochloric acid. Therefore, in the past thirty years, it has been widely used in harsh corrosive environments, such as chemical industry, petrochemical industry, flue gas desulfurization, pulp and paper making, environmental protection and other industrial fields. The various corrosion data of Hastelloy C-276 alloy are typical, but they cannot be used as specifications, especially in unknown environments, and materials must be selected after testing. There is not enough Cr in Hastelloy C-276 alloy to resist corrosion in strong oxidizing environments, such as hot concentrated nitric acid. The production of this alloy is mainly for chemical process environments, especially in the presence of mixed acids, such as the discharge pipe of flue gas desulfurization systems.

Hastelloy C-276 alloy can be used as flue gas desulfurization components in coal-fired systems. In this environment, C-276 is the most corrosion-resistant material. The following table shows the comparative corrosion test results of C-276 alloy and typical 316 in the "green death" solution of the flue gas simulation system.

C-276 alloy has good corrosion resistance to mixed acid and salt solutions containing chloride ions. The addition of Cr, Mo, and W in Hastelloy C-276 alloy greatly improves the resistance of C-276 alloy to pitting corrosion and crevice corrosion. C-276 alloy is considered inert in seawater environments, so C-276 is widely used in marine, salt water and high chlorine environments, even in strong acid and low pH conditions.