HONG KONG — A Shanghai court imprisoned a tycoon who used a mountain of debt to buy the Waldorf Astoria hotel. Small Chinese companies are increasingly saying they cannot repay their bills, as money gets more expensive or harder to find. For other private businesses, the cost to borrow has shot up.

Faced with the looming consequences of a decade-long borrowing binge, the Chinese government is intensifying its efforts stamp out risky lending and speculative froth from the world’s second-largest economy. To do it, Beijing is putting the brakes on shadowy forms of underground lending and making public spectacles of the worst offenders, even as it takes steps to ensure that small investors and the broader economy are not shaken.

The most recent and visible sign came Thursday morning, when a court in Shanghai sentenced Wu Xiaohui, the founder of one of China’s biggest insurance companies, to 18 years in prison. Mr. Wu, a former car salesman who rose to become one of China’s most successful businessmen, was charged in March with fraud and accused of using his company, Anbang Insurance Group, to cheat investors out of more than $10 billion.

But other signs are emerging, including loan defaults from a growing number of companies and rising interest rates for many borrowers.