Percussion Welding for Aerospace Heating Elements: Joining Nichrome, Kanthal, and Resistance Wire to Copper Leads 

Aerospace heating elements — de-icing systems, environmental control units, fuel line heaters, and sensor preheaters — use resistance wire (Nichrome, Kanthal, Evanohm) to convert electrical energy into heat. The engineering challenge is at the termination point: where the resistance wire must be connected to a copper or nickel lead wire for power delivery.

This termination is a dissimilar metal joint between materials with very different properties:

• Nichrome (Ni-Cr): Melting point ~1,400°C, high resistivity, oxidation-resistant
• Kanthal (Fe-Cr-Al): Melting point ~1,500°C, extremely high resistivity, forms protective alumina layer
• Copper lead wire: Melting point 1,085°C, very low resistivity, high thermal conductivity

The melting point mismatch and vastly different thermal conductivities make conventional fusion welding unreliable. TIG welding overheats the copper before the Nichrome reaches welding temperature. Soldering introduces a weak link with lower temperature rating than the heating element itself. Mechanical connections (crimps, wraps) loosen under thermal cycling.

Percussion welding completes the joint in under 3 milliseconds — fast enough that heat does not conduct down the resistance wire and change its calibrated resistance value, and fast enough that the copper lead does not overheat or anneal.

The process works as follows for a typical Nichrome-to-Copper heating element termination:

1. The Nichrome resistance wire and copper lead wire are positioned in the 726 Bench Fixture with a controlled gap between their ends
2. The 858 Percussion Welder discharges a stored electrical arc across the gap, melting a thin surface layer on both wires simultaneously
3. A percussive impact drives the wires together, forging the molten surfaces into a molecular bond
4. The joint is complete in under 3 milliseconds with near-zero heat-affected zone on both sides

The following parameters are from MTI Micro Welding's laboratory-verified weld schedules. These are starting points — we recommend varying one parameter at a time and testing the result for your specific application.

Nickel to Kanthal

Wire Dia.	Velocity	Time	Cap	Voltage	Pulse
.015"	70V	1.00 ms	2	50V	Short

Copper to Chromel (Ni-Cr thermocouple alloy)

Wire Dia.	Velocity	Time	Cap	Voltage	Pulse
.030"	55V	2.50 ms	3	50V	Short
.040"	55V	2.00 ms	3	50V	Short

Copper to Nickel (common lead-to-element connection)

Wire Dia.	Velocity	Time	Cap	Voltage	Pulse
.018"	70V	1.50 ms	3	70V	Short
.025"	62V	1.00 ms	2	55V	Long
.040"	48V	2.00 ms	3	65V	Short

Tungsten to Nichrome

Wire Dia.	Velocity	Time	Cap	Voltage	Pulse
.010"	48V	5.00 ms	2	40V	Long

View all 120+ verified weld schedules →

Aerospace heating elements operate in environments where failure is not an option — de-icing systems at -40°C, engine compartment sensors at 800°C+, and vibration levels that loosen mechanical connections. The percussion-welded termination provides:

• Full electrical conductivity at the joint — no added resistance at the transition point between heating element and lead wire
• Preserved resistance wire properties — the sub-3ms weld cycle does not alter the calibrated resistance of the heating element
• No contamination — no flux residue, no solder, no braze alloy that could outgas in vacuum or degrade at operating temperature
• Vibration resistance — the molecular bond does not loosen or fatigue like crimped or wrapped connections under sustained vibration per MIL-STD-810

Learn more about percussion welding for heater elements →