**2. Development status of hardbanding materials**

The development process of the hardbanding material is divided into two stages: the first stage is the cemented carbide material stage (from the 1930s to the early 1990s); the second stage is the "casing-friendly" material stage (from the 1990s to the present) [7].

## **2.1 Cemented carbide material stage**

The cemented carbide hardbanding material was invented and marketed by Hughes Tool Company in the 1930s, which was designed to prevent the abrasive wear of drill pipe joints in the open hole section and improve the service life of drill pipe. This hardbanding material is composed of low carbon steel matrix and carbide particles, which is a very effective method of protecting drill pipe joints in shallow wells (<1500 m) and vertical wells (well deviation below 2°) [8, 9].

But as wells become more complex, the depth of the well is getting deeper, and the angle of the well is getting larger. The casing failures caused by the hardbanding of cemented carbide became more and more serious, which had aroused wide concern [10]. A lot of experimental studies have shown that during rotary drilling and tripping, the cemented carbide particles embedded in it will be soon exposed, because of the relatively soft base alloy of this wear-resistant belt. These exposed cemented carbide particles will cause serious abrasive wear on the casing wall and finally cause the casing failure.

In order to avoid the loss caused by casing failure, it was decided to stop using the cemented carbide hardbandings. Only the smooth drill pipes without hardbanding or other anti-wear technologies (such as rubber drill pipe protector, casing pipe blast joint, etc.) were allowed. Other anti-wear technologies could reduce casing wear to some extent but were generally faced with many problems, such as high cost, complex structure, difficult installation, low life, easy to cause downhole accidents, etc. [11].

Therefore, the major technical service companies began to develop new materials to replace the cemented carbide material. These materials are generally characterized by low friction, small wear to the casing, and high hardness, which can

protect the drill pipe joint to a certain extent. Since then, the development of drill pipe joint hardbanding material has entered the stage of "casing-friendly" material.
