This paper addresses the looming threat of quantum computing over blockchains by introducing a quantum-enhanced security solution, QKD, with the BB84 protocol. This approach targets a private blockchain infrastructure to replace the conventional cryptographic strategies with quantum-secured communication. The blockchain framework developed here is on Hyperledger Fabric, and quantum-secured smart contracts are designed in Solidity and deployed on the Ethereum testnet. Bridging the simulation gap are five QKD-enabled nodes forming the consensus network using IBM Quantum Experience and Hyperledger Fabric. Performance metrics include Security breaches, transaction latency, throughput, and scalability. Results show total resistance to eavesdropping by the QKD-enhanced blockchain, exhibiting zero security breaches in 1000 attempts; however, transaction latency at 200 ms and throughput of 100 transactions per second are quasi-scalably affected with QKD introduction into the system. Note that slight impact on scalability due to node increase is quite negligible within test parameters set for this experiment. Future works should focus on optimising computational overhead introduced by QDs in securing blockchain systems without compromising security obtained against eavesdropping on transactions.