Thermal fatigue study of tungsten alloy WNi28Fe15 cladded on AISI H13 hot work tool steel

• Thermal fatigue resistance of WNi28Fe15 alloy was studied.
• WNi28Fe15 alloy in combination with GTAW results in prolonged lifetime of cladded specimens.
• The tempering effect results in decrease of hardness of heat treated AISI H13 steel.
• WNi28Fe15 alloy has lower coefficient of linear thermal expansion compared to AISI H13 hot work tool steel.

In this paper thermal cycling of tungsten alloy WNi28Fe15 used as a filler material for cladding of the surfaces on the high pressure die casting tools is presented. Gas tungsten arc welding was used for deposition of the tungsten alloy in a form of a welding rod on the cylindrical specimens made of AISI H13 hot work tool steel. High frequency generator working with 20 kHz was used for thermal cycling of the 40 mm high specimens with the diameter of 30 mm. Water with a temperature of 8 °C was flowing through the internal hole of the specimen. Each thermal cycle consisted of 5 s long heating section and 30 s long cooling section. The temperature of the surface during thermal cycling was measured using infrared camera. The resulting clad was studied by means of microstructural analysis. The results have shown superior thermal fatigue resistance of cladded layer compared to reference heat treated hot work tool steel AISI H13. Surface hardness of the specimens cladded with tungsten alloy is approximately 100 HV0.5 higher compared to heat treated AISI H13 steel at the end of thermal cycling. Additionally coefficient of the linear thermal expansion was measured for WNi28Fe15 alloy in the range from room temperature to 1100 °C. An average value of the coefficient of the linear thermal expansion in the range between 25 °C and 700 °C is 12.3 · 10− 6 K− 1.