An EGR cooler includes an elongated, stainless steel cooler housing with a first end having a stainless steel end plate and a second end opposite the first end, and an Inconel diffuser having an inlet end defining a gas inlet and an outlet end welded to the stainless steel end plate. The stainless steel end plate having a first thickness and the outlet end of the Inconel diffuser including a sidewall having a second thickness that is 50% or less of the first thickness.