In 6G networks, network softwarization is the crucial attribute, enabling to softwarize and virtualize dedicated hardware into software blocks and general-purpose hardware. Deploying chained software blocks on top of underlying general-purpose hardware is generally abbreviated as service function chain (SFC) in softwarization research. Though abundant results have been published, a variety of security challenges in SFC area, such as the decentralization, transparency, risks of data interoperability and privacy vulnerabilities, have not been well addressed yet. Blockchain emerges in recent years and is widely accepted as the most promising technology to deal with security and privacy issues in softwarized 6G networks. In this paper, the state-of-the-art survey on blockchain-enabled SFC in existing networks is conducted. Especially, typical SFC solutions, incorporating blockchain, are discussed and described. Next, major findings, derived from existing studies on blockchain-enabled SFC, are summarized and discussed. Finally, emerging directions are shed for blockchain-enabled SFC in 6G networks.