Western Digital Corp. plans to approach lenders next week to start syndicating a $18 billion debt package backing its takeover of SanDisk Corp. in this year’s biggest test of the leveraged loan market’s strength.

Banks financing the deal will hold a meeting with investors March 15 to seek support for a $6 billion term loan B, typically purchased by mutual-fund investors, hedge funds and collateralized-loan obligations, according to people with knowledge of the matter, who asked not to be identified as the information isn’t public. It would be the biggest institutional loan since Avago Technologies Ltd. sold $9.75 billion of debt in November, according to data compiled by Bloomberg.

The push for financing by the drive maker comes as loan funds reported $425 million of inflows, the biggest weekly deposit since July, according to Wells Fargo & Co. New deals are trickling back into the market after a month-long rally has pushed up the prices for below investment-grade debt.

The transaction will be a gauge for investor demand to fund large deals, according to Jeffrey Ross, a partner at Debevoise & Plimpton, who advises on acquisitions and financings. “There certainly are green shoots out there but I haven’t heard people exuberant about where markets stand,” Ross said.

The Western Digital financing includes $9 billion in term loans, $8.1 billion in bridge loans, and a $1 billion revolving credit line, according to regulatory filings. The company is buying SanDisk to gain access to a supply of semiconductors that are at the heart of a fast-growing type of computer storage. SanDisk is one of the largest makers of the NAND flash chips, which use less power and access information faster, making them more beneficial for cloud-computing data centers.

JPMorgan Chase & Co., Bank of America Corp., Credit Suisse Group AG and Royal Bank of Canada have committed to provide the financing and will be arranging the debt sale.