Quenched and tempered HB220-270, nitriding HRC>65, foreign countries use titanium carbide coating to improve the corrosion resistance of the screw surface, but it is reported that its wear resistance is not good enough.

Foreign countries have adopted a series of measures to improve the wear resistance and corrosion resistance of the screw. One way is to use highly wear-resistant and corrosion-resistant alloy steel. Such as 34CrAlNi, 31CrMo12, etc. There is also a method of spraying Xaloy alloy on the surface of the screw. This Xaloy alloy has high wear and corrosion resistance.