Back roller and preparation method thereof, and coating machine

A back roller, comprising:

• a roller body, having an axis and a roll surface disposed around the axis;
• wherein the roller body comprises a first part and two second parts, the first part has the axis and the roll surface, and the two second parts are respectively connected to two opposite ends of the first part along a direction of the axis;
• and
• a wear-resistant layer, covering the roll surface, wherein
• Vickers hardness of the wear-resistant layer is denoted as H, and 800 HV≤H≤1400 HV:
• wherein thickness of the wear-resistant layer is denoted as h, and h>0.1 mm;
• and
• wherein the wear-resistant layer is formed as a tungsten carbide plating;
• wherein the first part is made from a chromium-containing alloy steel having a uniform crystal distribution with retained austenite having been martensitized;
• and
• the two second parts are respectively embedded and hot fitted in two opposite ends of a through-hole in the first part, wherein welding joints are formed between the two second parts and the first part, wherein the roll surface is a frequency quenched surface.