TH420 Spray Wires
TH420 is a 400 series stainless wire containing chromium, and carbon. This is a very economical spray material and likely the most used in the thermal spray industry, it has excellent wear characteristics with unlimited build up capabilities for most applications. It can be single point tooled for many applications, however to obtained a very smooth finish grind finishing is required.
Average Bond Strength:
3,000 PSI (tested on ordinary steel in accordance to ASTM C 633-79). TH420 is self-bonding to materials with moderate hardness, whereas a 3-5 mil surface preparation profile can be obtained. For spraying onto hard materials where a surface profile cannot be obtained, a bond coat of TH-202 is recommended.
Thickness Limits:
TH420 is considered a low shrink high build material, for many objects unlimited thickness can be obtained. Coating thickness is dependent on several factors one being the substrate hardness and ability to obtain a quality surface preparation.
Ductility
The sprayed coating will withstand severe bending and stress loading of the substrate material. The coating will maintain character up to the elastic limit of the substrate material.
Hardness:
Rc 40
Parameters:
1/16" (1.6mm), 3/32" (2.3mm) 1/8" (3.2mm) diameter wire Current, Amps 150-350 Volts 33-36 Air Pressure, psi 90-100 Spray Distance 6"-10" Thickness Per Pass 1-2 mils
Spray Rate:
TH420 sprays very well, and is considered one of the smoothest spraying wires with trouble free operations. 1/16" (14 gauge, 1.6mm), 3/32" (11 gauge, 2.3mm) dia., and 1/8" dia. wire provide excellent coatings where finish machining is required. The 1/8" diameter sprays at 50 pounds per hour in Thermion Arc Spray systems.
Surface Finish:
The sprayed coating is best finished by grinding, an RMS 12 or better (mirror) finish can be obtained by grinding and polishing.
Use:
TH420 is recommended for use on items that are subject to wear, and/or wear, corrosion, and moderate heat oxidation. Wear items include crankshafts, seal areas, fan blades, Yankee dryers etc. This material works well on cast iron due to the close match of coefficient of expansion. This material has been the workhorse of the industry for wear resistance coatings; it performs well for crankshaft journals and similar type applications. It can be single point tooled on a lathe, or finished by grinding to achieve a very smooth finish.