Surface modification technology is one of the methods to improve the wear resistance of stainless steel surfaces.


1. Ion implantation

Ion implantation uses an accelerated and separated high-energy ion beam to act on the surface of the material to produce an implanted layer of a certain thickness, thereby changing the surface properties of the material. The specific method is: place the workpiece (metal, alloy, ceramic, etc.) in the vacuum target chamber of the ion implanter, and accelerate, focus, and inject the ions of the required elements into the workpiece under a voltage of tens to hundreds of kilovolts. surface. The ion implantation method can be used to obtain different structures such as supersaturated solid solution, metastable phase, amorphous state, and equilibrium alloy, which greatly improves the performance of the workpiece.

The advantages are:
(1) Any element can be injected and is not affected by solid solubility and diffusion coefficient;
(2) The amount of element injection can be precisely controlled, enabling large-area and local surface modification;
(3) Performed under vacuum, the surface of the workpiece will not be oxidized;
(4) Two or more layers of composite coatings with different properties can be obtained, with little impact on the size of the workpiece;
(5) With the help of a magnetic analyzer, pure ion beam current can be obtained;
(6) The straight-forward nature of ion implantation and small lateral expansion are suitable for micro-machining requirements;
(7) High-speed ions can be injected into the metal matrix through the film, forming an alloy layer at the interface between the film and the matrix, enhancing the bonding force between the film and the matrix, and achieving radiation-enhanced alloying and ion beam-assisted enhanced adhesion.

weakness is:
(1) Metal ions have high melting point and high injection energy, so their use is limited:
(2) Irrigation and temperature rise sputter corrosion caused by high-dose implantation, as well as how to optimize sputtering and complex shape (inclined injection, rotational injection, column injection) injection, etc. are all problems that need to be solved day by day.


2. Laser surface treatment

Laser surface modification is a high-tech technology developed in the 1970s. It uses the characteristics of high brightness, high monochromaticity, high directionality and high coherence of laser to act on the surface of metal materials to improve the surface properties of the materials. In particular, improvements in material surface hardness, strength, and wear resistance have increased the service life of the product. Laser surface modification can be divided into laser surface phase change hardening, laser shock hardening, laser cladding, laser alloying and laser amorphization. From a process perspective, their respective characteristics are caused by different laser power densities acting on the material surface and different cooling rates.

The characteristics of laser surface treatment in stainless steel plate material processing are:

(1) Energy transfer is convenient, and the surface of the workpiece to be processed can be selectively and locally strengthened;
(2) The laser energy is concentrated, the processing time is short, the heat affected zone is small, and the workpiece deformation is small;
(3) Workpieces with complex surface shapes can be processed and automated production can be easily realized;
(4) The modification effect is more significant than ordinary methods, with fast speed, high efficiency and low cost;
(5) Usually it can only handle some thin sheet metals and is not suitable for processing thicker sheets;
(6) Since the damage of laser to human eyes affects the safety of workers, we must devote ourselves to the development of safety facilities.


3. Contour surface treatment

Chemical reactions in plasma are easier to carry out than thermochemical reactions. The charged particles in the discharge space (gas) have thermal motion, migration motion under the action of electric field, and diffusion motion in the direction of decreasing concentration of charged particles. In terms of technology, it can be divided into: plasma nitriding, plasma carburizing, carbonitriding, plasma sulfurizing, sulfur-nitrotriding, sulfur-carbonitriding, etc.

Plasma nitriding can greatly improve the hardness and wear resistance of stainless steel, but the corrosion resistance of the treated stainless steel decreases. The hardness of the ion nitriding surface layer is very high, and the maximum microhardness can reach 1290Hy3. Tian Xiubo et al. used immersed high-frequency high-pressure plasma nitriding (IHHPN) technology to perform low-temperature nitriding treatment on SS304 austenitic stainless steel. Under the treatment conditions of 300℃×2.5h, a 0.3um thick high-nitrogen layer was obtained, and the surface showed The microhardness is significantly higher than that of the untreated sample, and expanded austenite is formed in the modified layer.