A diaphragm valve including a valve body, a diaphragm assembly and an actuator assembly having a housing body that isolates the actuator from the ambient atmosphere. The diaphragm assembly is welded to the valve body to reduce and/or eliminate fluid leakage around the diaphragm assembly. Additionally or alternatively, the housing body for the actuator assembly may be welded to the valve body to reduce fluid leakage. The welding may be performed using ultrasonic welding techniques.