Issues To Be Aware Of When Hardening The Ball And Seat Of A Hard-Seal Ball Valve

The selection of valve ball and seat:

For metal hard-seal ball valves, the valve ball and seat materials are generally made of stainless steel or corrosion-resistant materials. Otherwise, the bonding layer between the hard alloy and the valve seat (or valve ball) is easily corroded by the medium, causing the hard alloy layer to peel off and affecting the life of the ball valve. In addition, appropriate hardening processes should be selected for different valve seat (or valve ball) materials. In the coal chemical industry, duplex stainless steel is widely used because it has good resistance to corrosion fatigue and wear corrosion.

Duplex Stainless Steel:

Duplex stainless steel is a type of steel that possesses both ferritic and austenitic microstructures, with each phase comprising approximately 50%. These two phases exist independently, resulting in performance characteristics that combine those of both austenitic and ferritic stainless steels. In ferritic stainless steel, prolonged holding at temperatures between 400-500°C leads to severe embrittlement, a phenomenon generally known as 475°C embrittlement. Temperatures exceeding 400-500°C degrade the properties of duplex stainless steel. If duplex stainless steel is subjected to spray welding or hard alloy overlay processes, the melting process

between the hard alloy and the substrate (generally at temperatures above 900°C) will damage the microstructure of the duplex stainless steel. Therefore, duplex stainless steel is not suitable for hard alloy overlay processes. Ultrasonic spraying is suitable for surface hardening of duplex stainless steel, but the hardening process must ensure that it does not damage the microstructure of the duplex stainless steel matrix.